Department of Astronomy Annual Report 2008

(1)

Observatory

University of Helsinki Annual Report 2008

Observatory P.O. Box 14, FI-00014 University of Helsinki, Finland

http://www.astro.helsinki.fi/

(2)

Foreword

The vision in the operational plan of the Observatory has been that we are the most efficient Finnish institute in researcher training in Astronomy during the period 2005–2010.

We can reach this vision only by maintaining an exception- ally high level of both research and teaching. Our long-term plan for the period 2005–2015 has consisted of ten operational measures, which have been systematically executed, followed and analysed in close collaboration with our three research groups, as well as with all students majoring in As- tronomy. Now in June 2009, we have already reached our vision, because 12 PhD theses have been completed after Jan- uary 2005. This is a fine achievement, considering that 9 PhD degrees were completed during the past ten years before Jan- uary 2005. The past year 2008 was exceptional: 3 PhD degrees, 1 Ph Lic degree and 11 M.Sc. degrees were completed.

The number of degrees completed between 1995 and 2008 has been as follows:

M.Sc. Ph.Lic. Ph.D.

1995 1 – 2

1996 – 1 –

1997 2 – 1

1998 – – 1

1999 4 – 2

2000 – – 1

2001 1 – 1

2002 – – –

2003 5 – 1

2004 2 – –

2005 2 – 2

2006 6 – 3

2007 5 – –

2008 11 1 3

We have also been able to maintain the high levels of the number of refereed articles published and external funding received. This volume and the funding of our research between 1995 and 2008 is illustrated in the attached figure. where the following notations have been used:

Number of articles in refereed journals (scale on the right) Budget funding from the University of Helsinki (scale on the left) ke.

•

Project funding for Observatory (scale on the left) ke.

◦

Project funding for Observatory including industrial sub- contracts (scale on the left) ke.

But success and hard work did not shield us. All small departments in Helsinki University will be merged with bigger departments (e.g. Astronomy with Physics). The reasons for this manoeuvre did not originate from the needs of research or education. Some said the reasons were financial and ad- ministrational, following from changes in the law of Finnish universities. Others invented other reasons. What would hap- pen, if Korkeasaari Zoo was ordered to put all animals into 30 cages? The last ones alive would probably be scavengers.

Would it not be interesting to see tigers and lions in the same cage?

It has been frustrating to experience how little we could actually control the course of events. Soon we shall no longer decide as an independent department what is best for Astron- omy in the University of Helsinki. Perhaps a faint glimmer of hope can be seen in the work of the group planning the future of Astronomy in the “new” Department of Physics. But it also now seems that all of us have to leave the 175 year old Ob- servatory building designed by Engel. I sincerely hope that such a mistake could be avoided. The ongoing year 2009 was nominated as the international year of Astronomy by United Nations. This completes the irony.

I wish to acknowledge the support of the Board of the Ob- servatory and the student association Meridian, and the work by faculty, staffand students in maintaining the high level of research and teaching at the Department of Astronomy.

Lauri Jetsu

Director of the Observatory Helsinki, June 6th, 2009

(3)

Photo: Leith Arar

(4)

1 Interstellar medium, star formation and magnetic activity of stars

Staffwith a Ph.D. Lauri Haikala, Docent Jorma Harju, Docent Thomas Hackman, Ph.D.

Mika Juvela, Docent Maarit Korpi, Docent Petri K¨apyl¨a, Ph.D.

Kimmo Lehtinen, Docent Kalevi Mattila, Prof.

Ilkka Tuominen, Prof.emer.

Ph.D. students Jouni Kainulainen, M.Sc Anne Liljestr¨om, M.Sc Tuomas Lunttila, M.Sc.

Johanna Malinen, M.Sc.

Minja M¨akel¨a, M.Sc.

Oskari Miettinen, M.Sc.

Jan Snellman, M.Sc.

Veli-Matti Pelkonen, M. Sc.

Marianna Ridderstad, M.Sc.

Ky¨osti Ryyn¨anen, M.Sc.

Olli Sipil¨a, M.Sc.

Associated scientists Axel Brandenburg, Ph.D., Prof.

(Nordita, Stockholm, Sweden), Thorsten Carroll, Ph.D.

(Astroph. Inst. Potsdam, Germany) Stephan Hotzel, Ph.D.

(Stuttgart, Germany) Ilya Ilyin, Ph.D.

(Astroph. Inst. Potsdam, Germany), Peter Johansson, Ph.D.

(University Observatory, Munich) Oleg Kochukhov, Ph. D.

Uppsala University, Sweden), Heidi Korhonen, Ph.D.

(ESO, Garching, Germany) Jaan Pelt, Ph.D.

(Tartu Observatory, Estonia) Peter Petrov, Ph.D.

(Crimean Astroph. Obs., Ukraine), Nikolai Piskunov, Ph.D., Prof.

(Uppsala University, Sweden), Mark Rawlings, Ph.D.

(JAC, Hawaii) Petri V¨ais¨anen, Ph.D.

(SALT, South Africa)

1.1 Research activities

The activities of the research group are directed to the following fields: (1) the formation of protostars in dense molecular cloud cores; (2) the properties and evolution of dust and molecular gas in interstellar clouds; (3) radiative transfer and magnetohydrodynamic (MHD) modelling of interstellar clouds and protostellar accretion discs; (4) MHD-modelling of solar and active late-type star convection and turbulent dynamos and related optical spectropolarimetric observations using inversion methods; (5) the optical and infrared extragalactic background radiation.

The group uses ground-based and space-borne optical/infrared, (sub)millimetre, and radio telescopes. The studies often are conducted in collaboration with research groups from other countries. As an example of the international as- pect, a Japanese-Finnish workshop ‘Interstellar matter and star formation in the Southern sky” took place at the Ob- servatory Aug. 5th to 7th. The Japanese participants were Prof. R. Kawabe (NRO/NAOJ), Prof. M. Momose (Ibaraki University), Dr. M. Hiramatsu (ASIAA, Taiwan) and Mr. Y.

Shimariji (NRO/NAOJ).

In recent years the ESO facilities have been of growing importance. The group has successfully performed several ESO/VLT observing programs and special attention is paid to the 12-m Atacama Pathfinder Experiment (APEX) and to the Atacama Large Millimetre Array (ALMA). APEX became publicly available in 2006 and ALMA will start its operation in 2010. The group has been well informed about available ESO telescopes and facilities: Mattila is since 2004 Finland’s representative in the ESO Council. Haikala is since 2007 (after Tuominen) Finland’s representative in the Scientific Tech- nical Committee. Harju is since 2004 member of the ALMA European Scientific Advisory Committee. In 2008, Juvela served a member and Harju an Expert Advisor in the ESO Observing Programmes Committee.

During the past several years ESA’s Infrared Space Ob- servatory (ISO) has been important for the group. The ex- ploitation of the ISO data has continued intensively, often in combination with near-IR and (sub)mm data from ESO and other ground based telescopes such as the Australian Tele- scope Compact Array, the Effelsberg 100-m and the Onsala 20-m radiotelescopes, and the 2.5-m Nordic Optical Tele- scope.

Based on its ISO experience, the group has been participating in the relevant Planck Surveyor science projects.

Among the other future ESA missions the group is particu- larly well-prepared to make use of the Herschel Space Obser- vatory mission and already participates in two Herschel open time key programmes. Our plans also include expanding and emphasizing our theoretical research of star formation and interstellar cloud physics.

Spectropolarimetric observations of active late-type stars using the high resolution Echelle spectrograph SOFIN at the Nordic Optical Telescope, La Palma, Spain, have continued successfully. The time series of spectroscopic observations for surface temperature maps already extend over 17 years.

Simultaneous local and global MHD modelling and model development has been actively carried out, applications ranging from the solar dynamo activity to the active rapid rotators followed up by the observational programme, also including MHD turbulence in accretion disks around pre- or protostellar cores, and molecular clouds and star-forming regions in galaxies.

1.2 Progress and highlights of scientific results in 2008

(for references see the list of publications)

1.2.1 Star formation in cometary globule GC 12

Low and intermediate mass star formation takes mostly place in isolated clusters and in low mass star forming regions. As the stars form in dense gas and dust clouds, which are tightly

(6)

Figure 1: Colour coded SOFI image of CG12. The J, H and K bands are coded in blue, green and red, respectively. Square root scaling has been used to better bring out the faint surface brightness structures.

concentrated in the plane, star formation far out of the plane is not a likely event. The well known nearby star forming regions have been studied in great detail from visual to radio wavelengths but less is known of star formation regions off the Galactic plane.

Despite being classified as a cometary globule, together with those in the Gum nebula, the high latitude globule CG 12 is actually a high latitude low and intermediate mass star formation region. With a galactic latitude of 21 degrees and at the distance of∼550 pc CG 12 lies more than 200 pc above the plane. The structure of the globule in molecular line emission has been extensively studied by us at SEST (Haikala and Olberg 2007) and at APEX (Haikala et al. 2006). CG12 is an active site formation site but only the brightest stars in the associated stellar cluster are known. We have conducted NIR JHK imaging of the globule with SOFI at the NTT telescope at La Silla. The imaging reveals several new deeply embedded member stars. The visual extinction towards the cluster members ranges from a few magnitudes up to about 40 magnitudes. Besides the two bright NIR reflection nebu- lae surrounding already known member stars, the SOFI imaging reveals an hour glass shaped nebulosity with a stellar like source at the “waist”. The hour glass lies at the centre of a highly collimated molecular outflow and is projected on a compact high density molecular core. The NIR imaging shows that active star formation is still going on in this low and intermediate mass star formation region high above the Galactic plane.

1.2.2 Prestellar and protostellar cores in Ori B9

Most stars form in clusters and smaller groups in the densest parts of giant molecular clouds (GMCs). By studying their physical and chemical characteristics, we hope to learn the conditions leading to protostellar collapse and the timescale related to this process.

We have carried out studies of the Ori B9 cloud. The 870 µm dust continuum was observed with the APEX telescope and data on the N₂H⁺(1−0) and N₂D⁺(2−1) lines were obtained with the IRAM telescope (see Figs. 2 and 3). To- gether with our previous H₂D⁺data (Harju et al. 2006), these were used to derive the degree of deuteration and other chemical characteristics. Using additional information from far- infrared Spitzer/MIPS maps, prestellar and protostellar cores were identified, and the evolutionary stages of the protostars were estimated. Two of the new submm cores are previously unknown class 0 protostellar candidates. The equal number of prestellar and protostellar cores found implies that the du- ration of the prestellar phase is comparable with the free-fall time. However, this interpretation can be questioned on the basis of chemical data. In some sources, depletion has lead to the disappearance of gas phase N2H⁺and the most abun- dant ionic species are probably H⁺and HCO⁺. The ionization degree was found to be x(e)∼10⁻⁷. The estimated ambipo- lar diffusion timescales are∼70−100 times longer than the free-fall time.

The mass of the clump associated with IRAS 05405-0117 was found to be∼14 solar masses. It has an elongated structure and, according to our data, consists of multiple low- to intermediate-mass dense cores. This suggest that it will even- tually form a small stellar group.

1.2.3 Near-infrared radiation as a tracer of cloud mass Near-infrared scattered light was observed towards several interstellar clouds using ESO/NTT and UKIRT telescopes.

In Corona Australis, in accordance with previous theoretical predictions (Juvela et al. 2006), the observed surface brightness could be explained by pure light scattering. The near-infrared surface brightness was found to be an accurate tracer of cloud mass. This means that observations of scattered light could become an important new method in studies of dense, quiescent clouds (Juvela et al. 2008; ESO press release 06/08).

Near-infrared observations and the role of dust scattering was investigated also in connection with external galaxies. We performed a radiative transfer simulation study where the near-infrared reddening signatures of extragalactic dust clouds were examined in a simple plane-parallel model mim- icking a face-on spiral galaxy (Kainulainen et al. 2008).

Based on the simulations, we described the expected wavelength dependency of the reddening signatures for different scale heights of the dust distribution and thereby showed that the observed wavelength dependency can be used as an indi-

(7)

Figure 2: The IRAS 05405-0117 clump region. The large plus signs mark the positions of our molecular-line observations. Also shown are the 24 µm peak positions of SMM 4 and IRAS 05405-0117, and the 24µm peak near SMM 5 (small green plus signs). The beam size is shown in the bot- tom left.

Figure 3: N₂H⁺(1−0) and N₂D⁺(2−1) spectra toward IRAS 05405-0117.

cator of the dust scale height. We also investigated the corre- lation between near-infrared reddening and total column density in the models, and concluded that only about 10-20%

of the total mass of dust clouds is recovered by their near- infrared reddening signature.

One question of great current interest in star formation is the possible connection between the mass function of dense cores in molecular clouds and the initial mass function of stars. Recently, dust column density data derived from near- infrared extinction maps were used to derive the core mass function for the nearby Pipe Nebula. Collaborating with the research group responsible for the observational work, we performed a simulation study where we examined the fea- sibility of the method employed in composing the mass function (Kainulainen et al. 2009). Using simulations, we described the accuracy at which the mass function can be derived from dust column density data, and how the essential parameters of the core population affect the accuracy. In particular, we showed that the core mass function can be derived quite reliably for relatively sparse clouds like the Pipe Neb- ula.

1.2.4 MHD phenomena: observations and modelling We have succesfully continued the investigation of the magnetic field structure, especially the polarity of the field in spots of two active longitudes, in active late-type stars (detected earlier on by the group using surface temperature maps and named as ”active star Hale rule”). Spectroscopic observations, based on which surface temperature maps have been inverted, were started in 1991 with the high resolution spectrograph SOFIN at the Nordic Optical Telescope, La Palma.

The time series collected since is one of the few most extensive and complete existing data sets to study long-term vari- ability (cycles) in active late-type stars. An important development is the magnetic inversions based on new spectropo- larimetic data with upgraded spectropolarimeter and reduction software, giving the first observational proof for the theoretical prediction of the magnetic field polarity. The work is done in collaboration with astronomers in Uppsala, Sweden, and Potsdam, Germany, most of the collaborators originally having worked in Helsinki Observatory and/or Oulu Univer- sity.

Simultaneously to the observations, local and global MHD models (PENCIL-CODE, MEFISTO; Korpi, Käpylä, Liljeström, Lindborg, Snellman) have been developed and utilized, to be able to investigate the transformation from solar-like dynamo activity to the activity seen in the active rapid rotators. This includes participation in a solar dynamo benchmark project which is likely to be helpful in the devel- opement and validation dynamo codes (Jouve et al. 2008).

Numerical modeling has yielded new results in a variety of systems: local turbulence models have been utilized to study the turbulent transport of angular momentum (K ¨apyl¨a

(8)

& Brandenburg 2008; Liljestr öm et al. 2009) and turbulent transport coefficients relevant for dynamo action (Bran- denburg et al. 2008; Mitra et al. 2009; Käpylä & Branden- burg 2009). Numerical studies of convection have, for the first time, revealed a large-scale dynamo (Käpylä et al. 2008, 2009a,b, in press). The latter project was accepted to the CSC grand challenge programme (DYNAMO08 PId by Ko- rpi), wherefrom 1 660 000 CPU hours of computing time was granted and used during the year 2008. Furthermore, a hydro- dynamic instability discovered earlier in isotropically forced turbulence was studied in detail numerically (Käpylä et al.

2009c).

1.2.5 Magnetic fields in interstellar clouds

Studies were carried out of the polarized sub-millimeter emission from dust grains in interstellar clouds. In a magnetic field, dust grains remain aligned as long as their rotation speed is significantly larger than their thermal rotation speed.

The grains are believed to be spinned up mainly by radiative torques. The efficiency of radiative torques was investigated using magnetohydrodynamic cloud simulations and detailed radiative transfer modelling (Pelkonen et al. 2009). Results indicate large spatial variations in the polarization efficiency.

In particular, in dense clouds, the dust emission is not likely to probe magnetic fields deeper than a few magnitudes in A_V. Through Zeeman effect, magnetic fields cause splitting of some radio lines. Because the split components have oppocite circular polarization, the line-of-sight component of the magnetic field can be estimated from the Stokes I and V spectra.

With radiative transfer modelling, three-dimensional magnetohydrodynamic simulations could be compared with existing measurements of the Zeeman effect in cloud cores (Lunttila et al. 2008). Good agreement was found between models of super-Alfv´enic turbulence, combined with self-gravity, and available observations of OH molecule lines. This suggests that the average magentic field of molecular clouds may be low and supports the idea of turbulence as a central factor behind the formation of self-gravitating cloud cores.

1.2.6 The Planck and Herschel satellite projects

We participate in several science projects within the Planck Surveyor satellite consortium. Our emphasis is on studies of dense interstellar clouds. Preparations were made to study Galactic cold and compact cloud cores using Planck data.

The population of cold cores (Tdust < 12 K) is still poorly known and Planck will be the first space borne mission that will be sensitive to their radiation. Methods were developed for the detection of cold cores and for the analysis of their dust emission. We also participate in some other Planck science projects, including the study of nearby galaxies.

We coordinated a successful open time key program proposal which was awarded ∼151 hours of observing time on the Herschel satellite. The aim of this project is to use

Herschel satellite for follow-up observations of a number of cold cloud cores detected in the Planck survey. Herschel will observe wavelengths close to the peak of dust emission, λ∼100−500µm, and, compared to Planck, will have much higher spatial resolution. Therefore, we will be able to study the internal structure of the selected cores, determine their evolutionary stages and their relation to future star formation.

We also participate in the Herschel key programme HiGal that will map a large fraction of the plane of our Galaxy.

1.2.7 Extragalactic background light

Using our understanding of the light scattering in dense interstellar clouds of dust, we have been developing a method for the detection of the optical extragalactic background light.

This is the so-called ‘shadow of a dark cloud method”. Based on our previous photometric EBL observing program we have developed a spectroscopic analogy for it. This new tech- nique utilizes the difference between the spectra of the diffuse galactic scattered light (absorption line spectrum) and the EBL (pure continuum spectrum with possible discontinu- ities). For the spectroscopic observing program we (Mattila, Lehtinen, Vaisanen) have received earlier 20 hours observing time at ESO VLT telescope and FORS instrument . For the ESO Period 82 18.5 hours were again allocated but only a few hours were realised in 2008/09. The reductions and analysis of these data are currently being performed by Mattila and Lehtinen. The modelling of the FORS spectra requires knowledge of the spectrum of the Local Interstellar Radia- tion Field (ISRF). A new synthetic spectral model is being developed along the lines of an earlier model by Mattila (1980 A&AS 39, 53) based on the high-resolution stellar spectrum library STELIB (Borgne et al. 2003, A&A 4002, 433).

Using data from the ISOPHOT instrument of the ISO satellite, we have completed a study of the extragalactic far- infrared background light (Juvela et al. 2009). The signal represents a significant fraction of the cosmic energy output from stars that has been reprocessed by interstellar dust and is redshifted to far-infrared wavelengths. Our study is the first independent test of the results obtained with the COBE satellite some ten years earlier. Our values are in agreement with the published COBE results, confirming the intensity of this extragalactic component at a level of∼1 MJy sr⁻¹ at wavelengths∼150–180µm.

1.3 External financing and resources

2008: Person-months of work: 177 Academy of Finland: 472 000e Ministry of Education: 100 000e University of Helsinki: 32 000e Foundations: 24 300e

(9)

1.4 Tests of learning

M¨akel¨a, Minja

M.Sc. thesis: High-latitude clouds in H-alpha;

2008, University of Helsinki, Department of Astron- omy

Eronen, Mikko

M.Sc. thesis: Chamaeleon I -t¨ahtiensyntyalueen kaukoinfrapunakartoitus; 2008, University of Helsinki, Department of Astronomy

Schultz, Minerva

M.Sc. thesis: Rikin kemian mallintamisesta raskaiden t¨ahtien syntyalueilla; 2008, University of Helsinki, Department of Astronomy

Yl¨osm¨aki, Maija

M.Sc. thesis: Chemistry of a dark cloud core;

2008, University of Helsinki, Department of Astron- omy

1.5 Visits abroad

Haikala, Lauri

European Southern Observatory, Chile, 29.2.–

12.3.2008

Onsala Space Observatory, Sweden, 15.–

19.3.2008

European Southern Observatory, Germany, 10.–

15.10.2008

ESO STC meeting; Garching, Germany, 20.–

22.10.2008

ESO STC meeting; Garching, Germany, 15.–

18.4.2008 Harju, Jorma

Universit¨at zu K¨oln, I. Physikalisches Institut, Germany, 6.2.–9.2.2008

15.1.2008

15.4.2008

29.5.2008

15.9.2008

20.11.2008

Juvela, Mika

Nordita, Stockholm (Turbulence and Dynamos meeting), Sweden, 17.–20.3.2008

IAS, Orsay (Planck workgroup 7 meeting), France, 5.–7.5.2008

ESO, Garching (OPC meeting), Germany, 26.–

30.5.2008

ESTEC, Noordwijk (Herschel KP workshop), The Netherlands, 1.–2.6.2008

Institute for Theoretical Physics (Z ¨urich), As- troSim conference in Ascona, Switzerland, 14.–

18.7.2008

MPIA, Heidelberg (Cosmic dust near and far, meeting), Germany, 8.–12.2008

MPIA, Heidelberg (Cosmic dust and radiative transfer, workshop), Germany, 15.–17.9.2008

Niels Bohr Institute, Copenhagen (Planck Science Team meeting), Denmark, 23.9.2008

ESO, Garching (OPC meeting), Germany, 17.–

21.11.2008

ESTEC, Noordwijk (Herschel KP workshop), The Netherlands, 4.–5.12.2008

Mattila, Kalevi

ESO Committee of Council, Stockholm, Sweden, 3.–4.3.2008

ESO Council, Prague, Czech Republic, 2.–

4.6.2008

Cosmic Dust Conference, Heidelberg, Germany, 9.–10.9.2008

ESO Committee of Council, Copenhagen, Den- mark, 6.–7.10.2008

ESO Council, Garching, Germany, 1.–3.12.2008 Pelkonen, Veli–Matti

CSI/ERCSC workshop at IPAC, Pasadena, CA, USA, 31.1.–9.2.2008

ESO observatory La Silla, Chile, 6.–18.4.2008 CMB Component Separation and The Physics of Foregrounds conference, Pasadena, CA, USA, 10.–

22.7.2008

CESR, Toulouse, France, 8.–13.12.2008 Miettinen, Oskari

Max-Planck-Institut f¨ur Radioastronomie, Heidel- berg, Germany, 5.–14.3.2008

Observations with the NRA VLA radiointerfer- ometer, New Mexico, USA, 5.–18.6.2008

(10)

Korpi, Maarit

NORDITA, Stockholm, Sweden, 17.3.–11.4.2008 NORDITA, Stockholm, Sweden, 6.–11.10.2008 K¨apyl¨a, Petri

NORDITA, Stockholm, Sweden, 16.3.–11.4.2008 Queen Mary College, University of London, U.K., 12.–17.5.2008

NORDITA, Stockholm, Sweden, 28.5.–6.6.2008 University of Leiden, The Netherlands, 18.–

22.8.2008

NORDITA, Stockholm, Sweden, 8.–12.9.2008 NORDITA, Stockholm, Sweden, 30.9.–

15.10.2008

NORDITA, Stockholm, Sweden, 1.–7.12.2008 Liljestr¨om, Anne

Turbulence and Oscillations in Accretion Discs, NORDITA, Stockholm, Sweden, 8.–10.10.2008

Observations with VLA; Albuquerque, USA, 4.–

18.6.2008 Tuominen, Ilkka

Turbulence and Dynamos meeting; Stockholm, Sweden, 16.–20.3.2008

Cool Star workshop; St. Andrews, U.K., 20.–

27.7.2008

IAU symposium, Tenerife, Spain, 2.–9.11.2008,

1.6 Papers read at scientific conferences, sym- posia, meetings etc.

Hackman, Thomas

”Correlating magnetic field strength and starspots on FK Com” (Korhonen, S.; Hubrig,; Th. Granzer;

T. Hackman; M. Schoeller; K.G. Strassmeier; M. We- ber)”, 15th Cambridge Workshop Cool stars, stellar systems and the Sun, 21.–25.7.2008, St Andrews, Scot- land, U.K., poster

Haikala, Lauri

”Cometary Globule 12, a star-forming region 200 pc above the Galactic plane ”, Milky Way Star Forma- tion, 3.–6.3.2008, Santiago, Chile, poster

”Atacama Path Finder Experiment APEX, the ESO submm telescope”, National meeting of the Finnish ESO scientists and students, 23.–24.10.2008, Tuorla Observatory, Finland, invited talk

”Cometary Globule 12, a high latitude low mass star formation region.”, National meeting of the Finnish

ESO scientists and students, 23.–24.10.2008, Tuorla Observatory, Finland

Harju, Jorma

”H2D⁺ as a probe of physical conditions in prestellar cores”, H2D⁺ meeting, 7.–8.2.2008, . Physikalisches Institut, Universit¨at zu K¨oln, Germany, invited talk

”Studies of prestellar and protostellar cores – from APEX to ALMA”, National meeting of the Finnish ESO scientists and students, 23.–24.10.2008, Tuorla Observatory, Finland

Juvela, Mika

”Scattered Near-Infrared Radiation – a New View of Interstellar Clouds”, XLII Annual Conference of the Finnish Physical Society, 27.–29.3.2008, Turku, Fin- land

”Simulated observations of turbulent interstellar medium”, Turbulence and Dynamos, 19.3.2008, Nordita, Stockholm, Sweden, invited talk

”Cold Cores”, Planck WG7 meeting, 6.5.2008, IAS, Orsay, France, invited talk

”Radiative transfer in the study of molecular clouds”, Frontiers in computational astrophysics, 14.7.2008, Ascona, Switzerland, invited talk

”Modelling and observations of scattered light and thermal emission by dust ”, Cosmic dust near and far, 8.–12.9.2008, Heidelberg, Germany, poster

”Radiative transfer of AMR grids”, Cosmic dust and radiative transfer, 17.9.2008, Heidelberg, Ger- many, invited talk

”High Resolution Mapping of Interstellar Clouds with NIR Scattered Light”, National meeting of the Finnish ESO scientists and students, 23.–24.10.2008, Tuorla Observatory, Finland, invited talk

Korpi, Maarit

”Suppression of MRI by supernova explosions in galactic disks”, Turbulence and dynamos, 17.–

20.3.2008, Nordita, Stockholm, Sweden, invited talk

”MRI in forced turbulence”, Turbulence and oscillations in accretion disks, 1.–15.10.2008, Nordita, Stockholm, Sweden

”Stellar nonlinear dynamos: observations and modelling”, Cosmic Magnetic Fields, IAU Symposio 259, 3.–7.11.2008, Puerto Santiago, Tenerife, Spain, poster

”Dynamically dominant magnetic fields in the diffuse interstellar medium”, Cosmic Magnetic Fields, IAU Symposio 259, 3.–7.11.2008, Puerto Santiago, Tenerife, Spain, poster

(11)

K¨apyl¨a, Petri

”Turbulent diffusivity quenching due to large- scale magnetic fields”, Turbulence and Dynamos, 16.3.–11.4.2008, Nordita, Stockholm, Sweden

”Large-scale dynamos in turbulent convection with shear”, Pencil Code Workshop 2006, University of Leiden, The Netherlands

”Convective angular momentum transport in accretion discs”, Turbulence and oscillation in accretion discs, Nordita, Stockholm, Sweden

Lehtinen, Kimmo K.

”Optical and nearIR observations of surface brightness of dark clouds”, National meeting of the Finnish ESO scientists and students, 23.–24.10.2008, Tuorla Observatory, Finland

Mattila, Kalevi

”Neljä vuotta ESO-jäsenyyttä”, National meeting of the Finnish ESO scientists and students, 23.–

24.10.2008, Tuorla Observatory, Finland, invited talk

”Avaruuden pilvet ja t¨ahtien synty” (Clouds of space and the birth of stars), From the Core of the Earth to the Space symposium, Finnish Academy of Science and Letters 10 years, 11.1.2008, Helsinki, Finland, invited talk

”E-ELT, Preparing for the Construction of the Eu- ropean Extremely Large Telescope”, Finland and the European research infrastructure projects, 6.2.2008, Helsinki, Finland, invited talk

”The spectrum of the ISRF as observed via the scattered light from a dust cloud”, Cosmic Dust Con- ference, 8.–12.9.2008, Heidelberg, Germany, poster Miettinen, Oskari

”The initial conditions of star formation in Ori B9 – N₂H⁺, N₂D⁺, and dust emission”, National meeting of the Finnish ESO scientists and students, 23.–

24.10.2008, Tuorla Observatory, Finland Pelkonen, Veli–Matti

”The Polarization of Dust Emission by Radiative Torque Alignment”, XLII Annual Conference of the Finnish Physical Society, 27.–29.3.2008, Turku, Fin- land

”Observing a Corona Australis cloud filament in NIR scattered light”, National meeting of the Finnish ESO scientists and students, 23.–24.10.2008, Tuorla Observatory, Finland

Ridderstad, Marianna

”The orientation of the northern gate of the Goseck solar observatory”, Cosmology Across Cul- tures – SEAC 2008, 7.–14.9.2008, Granada, Spain, poster

Tuominen, Ilkka

”Stellar nonlinear dynamos: observations and modelling”, Turbulence and dynamos, 17.–20.3.2008, Nordita, Stockholm, Sweden

”Stellar nonlinear dynamos: observations and modelling”, 15th Cambridge Workshop Cool stars, stellar systems and the Sun, 21.–25.7.2008, St An- drews, Scotland, U.K., poster

”Magnetic Doppler imaging of II Peg”, IAU Sym- posium 259: Cosmic magnetic fields: from planets to stars and galaxies, 3.–7.11.2008, Tenerife, Spain, poster

”Stellar nonlinear dynamos: observations and modelling”, IAU Symposium 259: Cosmic magnetic fields: from planets to stars and galaxies, 3.–7.11.2008, Tenerife, Spain, poster

”The surface magnetic field evolution of II Peg – A Zeeman-Doppler imaging approach”, IAU Sym- posium 259: Cosmic magnetic fields: from planets to stars and galaxies, 3.–7.11.2008, Tenerife, Spain, poster

1.7 Visiting academics

Haikala, Lauri

Kawabe, Ryohei, PhD, Prof, National Radio Ob- servatory, Japan, 4.–8.8.2008

Momose, Munetake PhD, Prof, Ibaraki Univer- sity, Japan, 4.–8.8.2008

Hiramatsu, Masaaki, PhD, Researher, ASIAA, Japan, 4.–8.8.2008

Shimariji, Yoshito, PhD Student, National Radio Observatory, Japan, 4.–8.8.2008

Harju, Jorma

Ristorcelli, Isabelle, PhD, researcher, Centre d’Etude Spatial des Rayonnements (CESR), Toulouse, France, 20.–23.1.2008

Klotz, Alain, PhD, Senior Lecturer, Centre d’Etude Spatial des Rayonnements (CESR) & Paul Sabatier University, Toulouse, France, 20.–23.1.2008

(12)

Juvela, Mika

Montier, Ludovic, PhD, CESR/CNRS-UPS, Toulouse, France, 21.–23.4.2008

Forero, Jaime, PhD, IAP, Potsdam, Germany, 17.–

20.6.2008

Rao, Srinivasa, PhD, Indian Institute of Astro- physics, Bangalore, Intia, 8.–15.10.2008

Marton, Gabor, MSc, E ¨otv¨os University, Bu- dapest, Hungary, 13.–17.10.2008

Mattila, Kalevi

Alves, Joao, Ph.D., Director, Calar Alto Observa- tory, Spain, 10.–13.11.2008

Oliver Krause, Ph.D., Head of IR Space Astron- omy, MPIA, Germany, 25.–29.8.2008

V¨ais¨anen, Petri, FT, South African Astronomical Observatory, South Africa, 22.–25.10.2008

1.8 Membership in scientific and scholarly so- cieties

Hackman, Thomas

Nordic Optical Telescope, Observing

Nordic Optical Telescope, Instrument User Group for High Resolution Optical Spectroscopy, Chair Haikala, Lauri

Europen Southern Observatory/Scientific Techni- cal Committee, expert

Harju, Jorma

European Southern Observatory, time allotment committee, 16.4.–5.6.2008, 13.10.–28.11.2008, expert

European ALMA Science Advisory Committee, expert

Finnish National Committee of URSI, Finland Juvela, Mika

The organizing committee of IAU Division VI, In- terstellar Matter, France

Steering committee of the project ASTROSIM, European Science Foundation, France

European Southern Observatory, Observing Pro- grammes Committee, Germany, expert

Mattila, Kalevi

Odin Science Team, 1991–

ISO/ISOPHOT Consortium, 1991–

Planck LFI, 1998–

Finnish National Committee for Astronomy (IAU), Finland, chair

European Southern Observatory, Council

Tuorla Observatory of University of Turku, advisory board, Chair

Ridderstad, Marianna

Finnish Astrobiology Network, 2006–

Tuominen, Ilkka

Finnish National Committee for Astronomy (IAU), representative for Finnish Academy of Science and Letters

Deutsche Forschunggemeinschaft, expert

1.9 Refereeing and Other Publishing Activities

Harju, Jorma

Astronomy and Astrophysics, referee (twice) Juvela, Mika

Publications of the Astronomical Society of Japan, Japan, referee

Nature, U.K., referee

Astrophysical Journal Supplement, USA, referee Mattila, Kalevi

Astronomy and Astrophysics, France, referee Astrophysical Journal, USA, referee

Monthly Notices of the R.A.S., U.K., referee Pelkonen, Veli–Matti

Monthly Notices of the R.A.S., referee Tuominen, Ilkka

Astronomy and Astrophysics, member of board of directors

(13)

2 High Energy Astrophysics

Project number 91525005

Research agreements Academy of Finland Tekes

ESA, ESO

Type of research Basic research, share: 50 % Development work, share: 50 % Director of research Docent Huovelin, Juhani

Telephone 19122948

Fax 19122952

E-mail Juhani.Huovelin@Helsinki.Fi

Senior (Ph.D. or higher) Juhani Huovelin, Docent Jukka Nevalainen, docent Thomas Hackman, Ph.D.

Linnea Hjalmarsdotter, Ph.D.

Ph.D. student(s) Lauri Alha, Ph.Lic.

Karri Koljonen, M.Sc.

Tuomas Lehto, M.Sc.

Sami Maisala, M.Sc.

Tero Oittinen, M.Sc.

Otto Solin, M.Sc.(Tech.) Auni Somero, M.Sc.

Tuure Takala, M.Sc.

Mikko Väänänen. M.Sc.

Students Jussi Ahoranta

Eero Esko Jasmin Haikonen Associated scientists Pasi Hakala, docent (Turku)

Diana Hannikainen, Docent (Helsinki Univ. of Technology)

2.1 General approach

The activities of high energy astrophysics research of HESA (High Energy Space Astronomy) are divided into three areas:

(1) fundamental science, (2) developing of new instruments for space research, and (3) developing of data analysis software.

The first part consists of scientific return (guaranteed time) from the instrument projects (INTEGRAL, SMART-1, Chandrayaan-1), complemented by data from other satellites (e.g. XMM-Newton, HST, RXTE, Chandra, Suzaku). The second part is a continuation to the ongoing hardware projects including research also in detector physics. The science topics addressed include coronae and flaring in active stars and the Sun, and studies of clusters of galaxies and related ques- tions in cosmology. In particular, the very broad spectral coverage (INTEGRAL) and the possibility for a very long mon- itoring (SMART-1, Chandrayaan-1), coupled to the sophisti- cated modelling, are the key ingredients of the science.

Development of new instruments is a natural continuation to the ongoing projects, providing valuable access to the guaranteed time also in the future. The aim is to utilise the ad- vances in instrument performances carried along with bigger telescopes, larger field-of-view and decreased noise of new systems in the future plans of ESA, NASA and JAXA (IXO, International X-ray Observatory, and Lobster). The specific improvements which are meaningful are: (1) the huge enhancement of sensitivity and spectral resolution with IXO, which enables studies of X-ray spectra of Galactic sources with the same quality we nowadays can investigate the so-

lar corona, (2) almost full sky field-of-view in X-rays with moderate spectral resolution (Lobster)) giving a freedom to select targets of interest and study their temporal and spectral behaviour in all time scales from seconds to months.

The systems under development are: (1) The SIXS instrument for BepiColombo (2) common DPU and onboard software of SIXS and MIXS instruments for BepiColombo, and (3) SQUID readout electronics for the X-ray Spectrome- ter (XRS) for IXO. The activities of HESA have resulted in the completion of three space science instruments, and a successful launch of INTEGRAL, SMART-1 and Chandrayaan-1 missions with our working hardware onboard. The scientific use of INTEGRAL resulted in a number of scientific papers published in 2003-8. SMART-1/XSM made effective observations of the Sun from March 2004 to August 2006. Sev- eral refereed papers on the instruments have already been published, and several papers on solar coronal science with very high quality data from XSM/SMART-1 are in prepara- tion, and one PhD thesis is just under submission. At present, the scientific utilization of INTEGRAL and SMART-1 con- tinues. Observation programs with other satellites (RXTE, XMM-Newton, Chandra, Suzaku) were continued.

The activities have also evolved, and grown to a higher level of collaboration with new plans for instruments and satellites, which combine the expertise and experience of the group and its collaborators. The wide scientific and techno- logical expertise within this framework have made it possible to start planning bigger contributions in international space science programs, e.g. participation at PI level in the next ESA cornerstone mission to Mercury (BepiColombo). We are also involved at Co-PI level in the India-ESA collabora- tive Moon mission Chandaryaan-1 (launched in 2008) with an XSM similar to that of SMART-1. The in-kind contribution of Finland’s entrance fee to ESO was completed successfully by the Finnish Sampo project, and ESO continued to support the development of ESO Reflex by our team with one and a half year’s extension with ESO funding.

2.2 Science topics

2.2.1 The solar corona

The aim of this research is to disentangle the properties of the hot solar corona by analysing the X-ray spectra obtained with our own instruments flying on-board space missions, like XSM/SMART-1 and XSM/Chandrayaan-1. The hot corona of the Sun radiates strongly in X-rays. The solar corona ex- hibits in apparently random intervals very strong eruptions, which are called flares. Big flares are associated with strong enhancement of electromagnetic emission at all wavelengths, and large amounts of accelerated energetic particles. The eruptions occur most frequently and they are strongest on average during Sunspot maximum.

In solar flares and also generally in the solar corona the radiation in X-rays dominates, which is due to the high tem-

(14)

perature of the ionized gas (plasma).

Our research aims at clarifying the physical mechanism of the eruptions by examining the X-ray spectrum and its vari- ation during flares, and by comparing different flares. Also time behaviour over longer time span is studied with the aim of studying the changes of the properties of solar corona during the Sunspot (11 years) cycle. The methods include developing improved theoretical models based on extensive new very high quality spectroscopic X-ray data.

The observations of the Sun are made with X-ray instruments on-board satellites. The most important of the instruments is the Finnish XSM X-ray spectrometer on the ESA’s SMART-1 satellite. In addition, data from the RHESSI and the GOES satellites are used as complementary sources of information. After the end of SMART-1 operations (September 2006), more similar data has already been received from a Finnish solar monitor on the Indian Chandrayaan-1 mission (launch in September 2008), and later, especially, with the Finnish solar monitor SIXS on ESA’s BepiColombo (launch scheduled in August 2014), which all are projects lead by the HESA group.

The data will enable obtaining a thorough new insight in electromagnetic processes and X-ray emission mechanisms in hot coronal plasma of the Sun, and will also form a basis in producing a realistic model database for modelling the X- ray spectra of other stars, with the aim of understanding their coronae.

Figure 4: The X-ray brightness of Ophiuchus cluster of galaxies obtained with XMM-Newton PN instrument. The white contours show the radio brightness obtained with VLA (Gov- oni et al., 2009).

2.2.2 Clusters of galaxies

Our research aims in characterising the thermal and non- thermal processes in clusters of galaxies. We use this information to derive the distribution of baryonic and dark matter in clusters and to constrain the cosmological parameters. We also derive properties of the relativistic electron populations and magnetic fields in clusters.

Figure 5: The distribution of non-thermal emission in Coma cluster as seen by XMM-Newton (color pixels). The blue contours show the 1.4 GHz radio halo (Deiss et al., 1997, A&A, 321, 55).

The main analysis tools utilized by us are high resolution imaging and spatially resolved spectroscopy of the hot intra- cluter gas. For this work we use X-ray and gamma-ray data of clusters of galaxies obtained with XMM-Newton, Suzaku and INTEGRAL satellites. We have obtained observation time via our own proposals which we combine with the available archival data.

Since clusters of galaxies are massive and hot, they inter- act with the Cosmic Microwave background via the Sunyaev- Zeldovich effect. In a working group of Planck satellite, we are planning the usage of this effect based on the Planck data.

We are participating in a international project IACHEC which aims at studying the cross-calibration of high energy satellites. JN is leading the cluster working croup of the project. Comparison of X-ray measurements of clusters of galaxies allows us to estimate the calibration accuracy of different instruments. We are currently developing cluster-based calibration tools for the future X-ray missions.

(15)

2.3 Development of data analysis software

ESO-connected data analysis activities have also grown significantly since the beginning of Finland’s membership in 2004. The project, called ESO-Sampo, conducts development of science data analysis environment for ESO. Four IT professionals worked full time for the in-kind contribution in the period 1.1.2005- 31.1.2008 in a Tekes-funded project at the Observatory, University of Helsinki, and has continued the same work with partial funding from ESO since then. The main result of the project is the ESO Reflex workflow engine, an advanced science analysis environment which ESO plans to implement as standard ESO software for the reduction of VLT and other ESO data.

HESA team has also participated actively in the prepa- ration of national technology return from ESO. These have already lead to a request from ESO to continue ESO Reflex development by partial ESO funding, and a parallel development of an application for other sciences and also com- mercial use with Tekes funding, which are still an ongoing activities. Further, future activities from this are (1) a Tekes project for developing a Situation Awareness System using Multidimensional Information (MIFSAS), and (2) a proposal to the Academy of Finland for Development and Applica- tion of New Computational Methods and Analysis for Re- mote Sensing Data of Planets and the Earth (CorePlane).

2.4 External financing and resources

2008: Man-months of work: 108 Academy of Finland: 109 320e

National Technology Agency: 2 500 000e European Space Agency: 165 000e European Southern Observatory: 100 000e

2.5 Tests of learning

Alha, Lauri

Licentiate’s thesis: The performance of X-ray So- lar Monitor (XSM) and the first results; 2008, Univer- sity of Helsinki, Department of Astronomy

Takala, Tuure

M.Sc. thesis: Study of GOMOS instrumental age- ing and applicability for stellar spectroscopy; 2008, University of Helsinki, Department of Astronomy Ahoranta, Jussi

M.Sc. thesis: Measuring dark energy with super- novae Ia, Department of Astronomy

Raja-Halli, Arttu

M.Sc. thesis: Mass function of clusters of galaxies – a study on systematic uncertainties on cosmological parameters due to the mass-observable relation, De- partment of Astronomy

2.6 Visits abroad

Alha, Lauri

Chandrayaan-1 C1XS science team meeting;

UCL, London, U.K., 7.–8.2.2008 Esko, Eero

CIXS Science Team Meeting; Aberystwyth Uni- versity, U.K., 15.–18.10.2008

Huovelin, Juhani

Chandrayaan-1 CIXS science team meeting;

UCL, London, U.K., 7.2.2008

BepiColombo SWG meeting ESTEC; Noordwijk, The Netherlands, 26.–27.3.2008

ESO Reflex project meeting, Munich, Germany, 2.4.2008

ESO-Reflex project meeting; Munich, Germany, 8.9.2008

BepiColombo SWG meeting; Sendai, Japan, 14.–

19.9.2008 Maisala, Sami

Sampo team meeting; ESO Garching, Germany, 16.–18.1.2008

SPIE Defence + security conference; Orlando, USA, 13.–22.3.2008

Sampo2 Kick-offmeeting; ESO, Garching, USA, 2.–3.4.2008

Sampo2 meeting; ESO,Garching, Germany, 8.–

9.9.2008

Interactive Tools/ESO-reflex meeting; ESO, Garching, Germany, 16.–18.12.2008

Nevalainen, Jukka

Universite Paris-Sud, France, 4.–7.5.2008 Granada conference center, Spain, 24.–31.5.2008 Oittinen, Tero

SPIE Defence + security conference; Orlando, USA, 13.–22.3.2008

Sampo2 Kick-offmeeting; ESO, Garching, Ger- many, 2.–3.4.2008

IBM Boeblingen Lab, application platform training; Stuttgart, Germany, 12.–13.6.2008

(16)

Sampo2 meeting; ESO,Garching, Germany, 8.–

9.9.2008

Interactive Tools/ESO-reflex meeting; ESO, Garching, Germany, 16.–18.12.2008

Väänänen, Mikko

7th International IGPP Conference, Kauai, Hawaii, USA, 6.–19.3.2008

2.7 Papers read at scientific conferences, sym- posia, meetings etc.

Esko, Eero

”Chandrayaan-1 XSM”, C1XS Science Team Meeting, 16.10.2008, Aberystwyth University, U.K., invited talk

”Mapping the non-thermal component in Coma cluster”, The X-ray Universe 2008, 28.5.2008, Granada, Spain, invited talk

Väänänen, Mikko

”Time evolution of the size of solar flare plasma loops along the main sequence”, 7th International IGPP Conference, 8.3.2008, Kauai, Hawaii, USA

2.8 Visiting academics

Bonamente, Massimiliano, PhD, assistant profes- sor, University of Alabama in Huntsville, USA, 18.–

22.5.2008

2.9 Membership in scientific and scholarly so- cieties

Finnish COSPAR committee, Finland

Research school for astronomy and space physics, Finland, board

Tuorla Observatory of University of Turku, advisory board

Academy of Finland assessor pool, Finland, expert

Finnish Space Committee (ANK), permanent expert

XMM-Newton AO8 Time Allocation Committee, 23.–26.1. 2008, U.K.

Planck Working Group 5, 30.3.2007–, expert International Astronomical Consortium for High Energy Calibration, 9.5.2007–, expert

2.10 Refereeing and Other Publishing Activi- ties

Earth and Planetary Science, Japan, referee Nevalainen, Jukka

Astrophysical Journal, referee

(17)

A group of Observatory faculty, students and staff March 26, 2008. (Photo: Anu Palo)

(18)

Photo: Leith Arar

(19)

3 Planetary System Research

Project number 02525008

Research agreements Academy of Finland Type of research Basic research Director of research Docent Muinonen, Karri

Telephone 19122941

Fax 19122952

E-mail Karri.Muinonen@Helsinki.Fi

Research staffwith a Ph.D. Karri Muinonen, Docent Kari Lumme, Prof. emer.

Serge Mouret, Ph.D.

Mikael Granvik, Ph.D.

Johanna Torppa, Ph.D.

Phd students Jyri N¨ar¨anen, M.Sc.

Dagmara Oszkiewicz , M.Sc.

Hannu Parviainen, M.Sc.

Antti Penttil¨a, M.Sc.

Jani Tyynel¨a, M.Sc.

Hannakaisa Lindqvist, M.Sc.

Students Jarkko Niemel¨a

Associated scientists Markku Poutanen, Prof.

Lauri Pesonen, Prof.

Jouni Peltoniemi, Docent Timo Nousiainen, Docent Jenni Virtanen, Ph.D.

3.1 Research activities

Research within the Planetary-System Research -group (PSR) at the University of Helsinki Observatory entails theoretical, observational, and experimental studies on key topics of solar-system exploration. In fundamental planetary physics, PSR theoretical research is focused on light scattering by single small particles, on multiple scattering by complex media of small particles, and the celestial mechanics of the few-body problem. Experiments have been carried out to measure backscattering characteristics of particulate media (scatterometer at the Observatory), to assess the X-ray fluorescence by planetary-regolith analog samples (at the Depart- ment of Physical Sciences), and to measure meteorite spectra in visible and near-infrared wavelengths (at the Geologi- cal Survey of Finland and at the Finnish Geodetic Institute).

Observations have been made using both space-based and ground-based telescopes.

The numerical method for computing coherent backscattering by complex particulate media developed at UHO has been successfully applied to polarimetric observations of transneptunian objects (TNOs). At ESO/VLT, PSR has continued to participate in polarimetric observations of TNOs, for example, through participation in the Large Program on the physical properties of TNOs. Furthermore, PSR has taken part in polarimetric observations of cometary nuclei at VLT:

these observations are the first-ever systematic polarimetric observations of cometary nuclei.

Among the highlights of the TNO studies was the dis- covery of two distinct polarimetric behaviours of transneptunian objects by Bagnulo et al. (2008B1). Polarimetric observations of the dwarf planet (136199) Eris were reported by Belskaya et al. (2008B1). Belskaya et al. (2008abB2) reviewed the polarimetric VLT observations, assessing the sur-

Figure 6: Linear polarimetry of nine TNOs as a function of phase angle. Two distinctly different populations are distin- guished: on the left, the large TNOs show rather shallow dependences; whereas, on the right, the small TNOs show steep dependences. The difference can be explained by the differing physical properties of the surfaces of large and small TNOs.

face properties of Kuiper-Belt objects and centaurs from photometry and polarimetry. The first polarimetric observations of a cometary nucleus, concerning comet 2P/Encke, were reported by Boehnhardt et al. (2008B1, 2008B2).

The single-scattering polarization and intensity mecha-

Figure 7: All dipoles of the Gaussian-random-sphere particle which have the intensity of the longitudinal component at least 30% from the maximum. The volume-equivalent-sphere size parameter x=8, the refractive index m =1.55, the rel- ative standard deviation of radiusσ=0.245, and the power- law index of the covariance functionν = 4. The incident polarization (blue color) and the wave vector (gray color) are shown on the lower left.

(20)

Figure 8: An aggregate of 100 spheres and its concave-hull transformations. The concave-hull transformation provides a method for generating nonspherical particle shapes and inhomogeneous internal compositions, which are essential quali- ties in modeling light scattering by small solar-system particles.

nisms deriving from the internal electric fields of Gaussian- random-sphere particles were studied by Tyynel ¨a et al.

(2008B1), similar to the study previously carried out for spherical particles. The study was further continued for ori- ented spheroids by Tyynel¨a et al. (2008B2). Tyynel¨a et al.

(2008abB2) carried out radar-scattering computations from spherical and spheroidal particles, as well as clusters of spherical particles in the C-band using the discrete-dipole approx- imation method (DDA). The results were compared to those from exact methods.

Parviainen and Lumme (2008B1) investigated scattering from rough thin films using DDA. Erkkil ¨a and Muinonen (2008B2) studied light scattering by inhomogeneous concave-hull-transformed clusters of spheres. Nousi- ainen et al. (2008B2) focused on optical modeling of thin calcite flakes using DDA. Zubko et al. (2008abcB2) studied light scattering by highly absorbing irregularly shaped particles, light scattering by agglomerated debris particles com- posed of highly absorbing material, and the applicability of DDA to conductive particles. Muinonen et al. (2008aB2) in- troduced diffuse scatterers in the ray-optics treatment for light scattering by particles large compared to wavelength.

In studies of orbit computation, Granvik and Muinonen (2008B1) presented a new method for the previously un- solved problem of linking scarce sets of astrometry of solar- system objects over apparitions. The new method is based on statistical orbital inversion, typically Ranging, and results from tests with simulated data were presented by Granvik and Muinonen (2008aB2). Granvik et al. (2008bB2) published an open-source orbit-computation package called OpenOrb which includes, for example, the statistical ranging method.

Virtanen et al. (2008B2) reviewed transneptunian orbit computation.

Figure 9: Al/Si elemental ratios on the Moon as measured with X-ray fluorescence spectrometers onboard the Apollo 15 and 16 missions. Red and blue imply high and low ratios, respectively. As the lunar silicon abundance as determined by these missions is relatively constant, this map depicts effec- tively the aluminium abundance. Picture courtesy of NASA.

(21)

Figure 10: Collapse of orbital-element p.d.f.s with improving accuracy of the observations. Sets of distributions each com- posed of 5000 possible orbit solutions for (4) Vesta obtained from simulated Gaia data for the epoch of 2010 Aug 5.0 TDT.

The distributions were obtained using four observations from a single scan (0.32 days observational time interval). Different colors correspond to different assumptions about the observational astrometric error in Right Ascension and Declination (red color impliesσα,δ=1.0 arcsec, greenσα,δ=0.1 arcsec, blueσα,δ=0.01 arcsec, and blackσα,δ=0.001 arcsec). The yellow asterisk indicates the end-of-mission least-squares solution. The distributions were obtained using MCMC ranging.

Figure 11: Comparison of reflectance spectra from a variety of meteorite subgroups. All of these, except one, are Chondrites that are primitive form of meterorite. The Eucrite is an HED that is from a differentiated body. The legend shows chart labels that consist of a letter and a number. The letter denotes the amount of free iron in the meteorite (High or Low) and the number denotes the amount of thermal alteration with 3 being the lowest and 6 the highest amount. Numbers below 3 refer to aqueous alteration. All groups have similar spectral characteristics with broad absorption bands (band I and band II) due to the presence of olivine and pyroxene. The bands are superimposed on a continuum that may increase or decrease with wavelength. Analyzing the features in the spectra can make a quantitive comparison between spectra.

(22)

Oszkiewicz et al. (2008B2) reported preliminary results of novel Markov-chain Monte-Carlo methods (MCMC) for asteroid orbit computation. The methods are to be applied, in particular, in the data analysis and processing chain for the ESA Gaia mission. Lindegren et al. (2008B2) described the training of the next generation of space astrometrists in the context of the ELSA project supporting the Gaia mission. Hildebrand et al. (2008B2) showed that the Near- Earth-Object Surveillance Satellite (NEOSSat) Mission will conduct an efficient space-based asteroid survey at low solar elongations. Grundy et al. (2008B1) developed a statistical ranging method for instrinsic orbit computation in binary systems such as those involving two asteroids or two TNOs.

They scheduled astrometric observations for (42355) Typhon Echidna based on the new method.

In studies of asteroid phase curves and lightcurves, Muinonen et al. (2008bB2) presented methods for the deriva- tion of empirical magnitude and polarization systems for asteroid phase curves. Their goal is to develop a new magnitude system for asteroids, revising the two-parameter H, G magnitude system. Torppa et al. (2008B1) provided asteroid shape and spin statistics from convex models. They showed that the resulting convex shape models can be fitted by ellipsoids at the 5% level but that the convex method is a key element in obtaining such ellipsoid models. Muinonen (2008B2) and Muinonen and Oszkiewicz (2008B2) provided preliminary results for lightcurve inversion using Markov-Chain Monte- Carlo methods.

Laboratory measurements on the effect that the physical properties of the regolith (primarily surface roughness) have on soft X-ray fluorescence spectroscopy of planetary surfaces were performed both at the University of Helsinki (in collaboration with the Department of Physics) and at the University of Leicester (UK) Space Research Centre. Preliminary results from these studies were published by N¨ar¨anen et al. 2008B1.

They confirmed that a hardening of the spectrum occurs as a function of growing phase angle and that the hardening is also larger for rougher surfaces. This effect will be important for the analyses of present and future X-ray spectrometer data from orbiting platforms (e.g., BepiColombo at Mercury and Chandrayaan-1 at Moon).

PSR has been collaborating with the Finnish Geodetic In- stitute during the past years in laboratory and field studies of multiangular light-scattering properties of terrestrial surfaces (such as understory vegetation of boreal forests). Peltoniemi et al. (2008B1) described parts of the equipment used in these studies and presented the highlights of the studies.

Parviainen and Muinonen (2008abB2) studied volume and surface shadowing in particulate random media, providing a realistic light-scattering model for rough particulate surfaces. Muinonen et al. (2008B2) assessed the scalar approxi- mation to coherent backscattering by spherical media. Foing et al. (2008B2), Koschny et al. (2008B2), and Grieger et al.

(2008B2) described the ESA SMART-1 mission lunar high-

lights, lunar science planning, and the coverage and pointing accuracy of SMART-1/AMIE images. PSR launched an in- depth study on the interpretation of the AMIE photometry:

the results of these investigations were submitted for publica- tion.

Preparations continued for the Marco Polo near-Earth- object sample return mission, with PSR represented in the ESA Science Study Team of the mission. The Marco Polo mission was described by Koschny et al. (2008B2) and Dotto et al. (2008B2).

3.2 External financing and resources

2008: Man-months of work: 100

Academy of Finland, ’Mercury, Lunar and Solar Science with BepiColombo and SMART-1: X-ray fluorescence from small-particle media’:

20 000e

European Commission, ’European Leadership in Space Astrometry’ (ELSA)’: 64 000e

Finnish Cultural Foundation 16 000e

Tekes project Nanopap (Improvement of Optical Properties of Paper by Increasing Refractive Indices of Materials): 21 000e

Tekes forest cluster project Re-engineering paper:

30 448e

3.3 Tests of learning

Granvik, Mikael

Ph.D. Thesis: Asteroid identification using statistical orbital inversion methods; 2008, University of Helsinki, Department of Astronomy

Torppa, Johanna

Ph.D. Thesis: Lightcurve inversion for asteroid spins and shapes; 2008, University of Helsinki, Depart- ment of Astronomy

Erkkil¨a, Hannakaisa M.Sc. thesis: Light scattering by small inhomogeneous solar-system particles; 2008, University of Helsinki, Department of Astronomy

3.4 Visits abroad

Muinonen, Karri

International Space Science Institute (ISSI), Switzerland, 6.–12.1.2008

Observatoire de Paris, France, 29.–30.1.2008 ESA/EST, The Netherlands, 18.–19.3.2008 ESA/ESTEC, The Netherlands, 26.–27.3.2008

(23)

ESA/ESTEC, The Netherlands, 13.–14.4.2008 Li`ege Observatory, Belgia, 14.–17.5.2008 Observatoire de la Cote d’Azur, France, 5.–

7.6.2008

AOGS meeting, Busan, South Korea, 12.–

20.6.2008

ACM’2008 meeting, Baltimore, USA, 13.–

18.6.2006

ELSA meeting, Barcelona, Spain, 31.8.–6.9.2008 ELS meeting, Hatfield, U.K., 7.–12.9.2008 ESA/ESTEC, The Netherlands, 29.–30.10.2008 Observatoire de Bordeaux, France, 19.–

22.11.2008

International Space Science Institute (ISSI), Switzerland, 30.11.–5.12.2008

Mouret, Serge

IMCCE – Paris observatory, France, 80 days Oszkiewicz, Dagmara

ESAC, Spain, 15.–19.1.2008 ESAC, Spain, 15.–20.6.2008 GAIA DPAC, Belgia, 14.–17.5.2008

Johns Hopkins University Applied Physics Labo- ratory, USA, 12.–19.7.2008

Li`ege University, Belgia, 24.–29.8.2008 Barcelona University, Spain, 29.8.–7.9.2008 Parviainen, Hannu

SMART-1 meeting; Madrid, Spain, 9.–12.4.2008 ELS XI meeting, U.K., 7.–12.9.2008

DPS 2008, USA, 9.–20.10.2008

MIXS IPDR; London, U.K., 10.–13.11.2008 Penttil¨a, Antti

ISSI – International Space Science Institute, Switzerland, 1.–5.12.2008

3.5 Papers read at scientific conferences, sym- posia, meetings etc.

Mouret, Serge

”Asteroid mass determination with Gaia mission”, The 10th Asteroids, Comets, Meteors, Baltimore, MD, USA

Muinonen, Karri

”Light scattering by solar-system small particles”, Visit at the Physics Department, University of Jyväskylä, 7.3.2008, Jyväskylä, Finland, invited talk

”Polarimetry of transneptunian objects and cometary nuclei with VLT”, National meeting of the Finnish ESO scientists and students, 23.–24.10.2008, Tuorla Observatory, Finland

”Planetary-System Research at UH/Obs”, Visit at the Finnish Geodetic Institute, 11.11.2008, Helsinki, Finland, invited talk

”Marco Polo: a near Earth object sample return mission”, Lunar and Planetary Science XXXIX, 10.–

14.3.2008, League City, TX, USA

”SMART-1 lunar highlights”, Lunar and Plane- tary Science XXXIX, 10.–14.3.2008, League City, TX, USA

”Coverage and pointing accuracy of SMART- 1/AMIE images”, Lunar and Planetary Science XXXIX, 10.–14.3.2008, League City, TX, USA

”Marco Polo: Near-Earth object sample return mission”, European Geosciences Union, General As- sembly, 13.–18.4.2008, Vienna, Austria, invited talk

”Physical properties of cosmic dust particles from light scattering”, Asia Oceania Geosciences Society, 16.–20.6.2008, Busan, South Korea, invited talk

”Marco Polo: NEO sample return mission”, Asia Oceania Geosciences Society, Annual Meeting, 16.–

20.6.2008, Busan, South Korea

”Polarimetry of transneptunian objects”, Astro- nomical Polarimetry 2008, 6.–11.7.2008, La Malbaie, Quebec, Canada

”First phase-angle resolved polarimetry of a bare comet nucleus: comet 2P/Encke”, Astronomical Po- larimetry 2008, 13.–20.7.2008, La Malbaie, Quebec, Canada, poster

”Science of Marco Polo: Near-Earth object sample return mission”, 37th COSPAR Scientific Assem- bly, 13.–20.7.2008, Montreal, Canada, invited talk

”Effect of regolith on planetary X-ray fluorescence spectroscopy: laboratory and numerical studies”, 37th COSPAR Scientific Assembly, 13.–20.7.2008, Montreal, Canada, poster

”Photometric study of the Moon with SMART- 1/AMIE”, 37th COSPAR Scientific Assembly, 13.–

20.7.2008, Montreal, Canada

”Planetary protection issues for the Marco Polo NEO sample return mission”, 37th COSPAR Scientific Assembly, 13.–18.6.2008, Montreal, Canada, invited talk

Department of Astronomy Annual Report 2008

Observatory

University of Helsinki Annual Report 2008

Observatory P.O. Box 14, FI-00014 University of Helsinki, Finland

Foreword

•

◦

Contents

1 Interstellar medium, star formation and magnetic activity of stars

1.1 Research activities

1.2 Progress and highlights of scientific results in 2008

1.3 External financing and resources

1.4 Tests of learning

1.5 Visits abroad

1.6 Papers read at scientific conferences, sym- posia, meetings etc.

1.7 Visiting academics

1.8 Membership in scientific and scholarly so- cieties

1.9 Refereeing and Other Publishing Activities

2 High Energy Astrophysics

2.1 General approach

2.2 Science topics

2.3 Development of data analysis software

2.4 External financing and resources

2.5 Tests of learning

2.6 Visits abroad

2.7 Papers read at scientific conferences, sym- posia, meetings etc.

2.8 Visiting academics

2.9 Membership in scientific and scholarly so- cieties

2.10 Refereeing and Other Publishing Activi- ties

3 Planetary System Research

3.1 Research activities

3.2 External financing and resources

3.3 Tests of learning

3.4 Visits abroad

3.5 Papers read at scientific conferences, sym- posia, meetings etc.