Department of Astronomy Annual Report 2007

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Observatory

University of Helsinki Annual Report 2007

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

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

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Foreword

The art of strategic planning and the execution of such plans is far from easy to master. One of the most famous plans in human history was the vision of presi- dent Kennedy in 1961 “of landing a man on the moon and returning him safely to the Earth”. This vision was so clear that all people involved into the execution of this plan understood it. The vision inspired and guided people towards trying to achieve an exceptionally high level of performance in their everyday work for the common plan. The definition of failure and success of the plan was also clear to everybody involved.

One can only hope that the University of Helsinki could formulate a similar strategic plan. A good vision is always ambitious. Such a vision defines failure and success, and hence it requires courage to express this vision precisely and openly. However, in absence of a clear vision the operations of an organization become unfo- cused. The leaders and the people involved are allowed to invent randomly selected criteria of success or failure both in the past and future operations of the organization itself. Some may even proudly call this academic freedom.

The vision in the operational plan of the Observatory is to be the most efficient Finnish institute in researcher training in Astronomy during the period 2005–2010. It is possible to reach this vision only if we have and can maintain an exceptionally high level of both research and teaching. The plan consists of ten operational measures, which are systematically executed, followed and analysed in close collaboration with our three research groups, as well as with all students majoring in Astronomy. Today, I am confident that we will succeed in reaching the vision of our operational plan.

Finally, I wish to acknowledge the support of the Board of the Observatory and the student association Meridian, and the work by faculty, staff and students in maintaining the high level of research and teaching at the Department of Astronomy. It is a privilege to be the director of this Observatory.

Lauri Jetsu

Director of the Observatory Helsinki, June 6th, 2008

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1 Strategy of the Observatory

In order to guarantee the development of astronomical research and teaching at the University of Helsinki, we aim for high quality research in those fields of Astron- omy that are pursued by the three research groups cur- rently working at the Observatory. During the period 2007–2009, one of the many goals in the strategy of the University of Helsinki is: “The university will continue to maintain a high profile in research and researcher ed- ucation.” This is very much the same goal which the Observatory emphasizes. The chosen strategic means are:

Participation in large astronomy and space research projects: We are now regularly utilizing the new resources offered by the Finland’s ESO (European Southern Observatory) membership, which started in July, 2004. Our increasing space research activity is also an investment to the future of Astron- omy. Our space research instrument development guarantees us future observing time with several satellites. High quality research requires access to the best existing instruments. The membership in international organizations offers this ad- vantage. The Observatory is actively involved in several ESA (European Space Agency) projects:

BepiColombo, Gaia, ISO, INTEGRAL, Herschel, Planck and SMART-1. Among our other ongoing joint research projects has also been the use of the Nordic Optical Telescope (NOT). Our active participation in the aforementioned, and several new international projects (e.g. ISRO’s Chandrayaan- 1, Marco Polo and XEUS satellites) secures conti- nuity of high quality astronomical research.

Increasing the research volume with external funding: Modern astronomical research is team work, where one often encounters the term “critical mass”

used in defining an effective research group. The Observatory encourages all efforts by the perma- nent staff to acquire external funding for their research groups. The most important funding sources are the Academy of Finland, the Finnish Funding Agency for Technology and Innovation, the Euro- pean Union, and private foundations.

Efficient PhD training: Ph.D. is the “basic degree”

for a researcher in Astronomy. We aim for a more efficient Ph.D. student supervision inside the research groups, which will lead to faster graduation.

We will continue active participation in the national “Graduate School for Astronomy and Space Physics”. In spring 2001, we initiated a program where a personal “teacher tutor” is appointed for every undergraduate student studying Astronomy as his/her main subject. In short, we do our best to encourage close connections between the students and the research groups.

Public Outreach: Astronomy enjoys the interest of the general public, and it is also a highly popular minor subject at the University of Helsinki. We aim to improve our efficiency in reporting about astronomical research, e.g. in the press, television and www. We also have a close connection to the Finnish Amateur Astronomer Association URSA.

The popularity of basic courses in Astronomy has been constantly growing. Continuous development of these basic courses also strengthens the motivation of students majoring in Astronomy. Another major goal for these basic courses is to teach the modern world pic- ture of natural science to the students in all faculties of the University of Helsinki. Direct connection between Astronomy courses and the research performed at the Observatory will be strengthened. As an example of the effectiveness of this strategy, the research projects performed by the students during an undergraduate level course have already been published in international refereed journals and several exercises in another course have lead to successful observing time proposals for space science missions.

Funding and volume of our research between 1995 and 2007 is illustrated in the figure on the next page.

The chosen strategy seems to predict a successful future for the Observatory of the University of Helsinki.

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Closed diamonds: Articles in refereed journals.

Scale on the right.

Closed squares: Budget funding from the University of Helsinki.

Scale on the left ke.

Closed circles: Project funding for Observatory.

Open circles: Project funding for Observatory including industrial subcontracts.

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2 Interstellar medium, star for- mation and magnetic activity of stars

Staff with a Ph.D. Lauri Haikala, Docent Jorma Harju, Docent Mika Juvela, Docent Maarit Korpi, Ph.D.

Petri K¨apyl¨a, Ph.D (Jan-Sept 07) 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.

Oskari Miettinen, M.Sc.

Veli-Matti Pelkonen, M. Sc.

Marianna Ridderstad, M.Sc.

Ky¨osti Ryyn¨anen, 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) Heidi Korhonen, Ph.D.

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

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

(Crimean Astroph. Obs., Ukraine), Mark Rawlings, Ph.D.

(JAC, Hawaii) Petri V¨ais¨anen, Ph.D.

(SALT, South Africa)

2.1 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. In recent years the ESO facilities have been of growing importance. The group has successfully performed several ESO/VLT observing programs (e.g., Kainulainen et al.

2007). Special attention is paid to the 12-m Atacama Pathfinder Experiment (APEX) and to the Atacama Large Millimetre Array (ALMA). APEX became pub- licly 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 Technical Committee. Harju is since 2004 member of the ALMA European Scientific Advi- sory Committee. Juvela became a member and Harju an Expert Advisor of the ESO Observing Programmes Committee in 2007.

During the past several years ESA’s Infrared Space Observatory (ISO) has been important for the group.

The exploitation of the ISO data has continued inten- sively, often in combination with near-IR and (sub)mm data from ESO and other ground based telescopes such as the Australian Telescope Compact Array, the Effels- berg 100-m and the Onsala 20-m radiotelescopes, and the 2.5-m Nordic Optical Telescope.

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 particularly well-prepared to make use of the Herschel Space Observatory mission. 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.

2.2 Progress and highlights of scientific results in 2007

(for references see the list of publications)

2.2.1 Deuterium fractionation and the degree of ionization in dense star-forming cores Most of the Galactic star formation takes place in clusters and smaller groups which are embedded in the dens- est parts of giant molecular clouds (GMCs). The frag- mentation of molecular clouds results in a dense struc- tures such as filaments and clumps which contain still denser cores. By studying the physical and chemical characteristics of these cores, one hopes to understand how fragmented clumps evolve and form stars. The 870 µm submillimetre dust continuum observations toward the Ori B9 cloud were carried out in 2007 Au- gust 4 with the 295 channel bolometer array LABOCA

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Figure 1: N2H⁺(1−0) and N2D⁺(2−1) spectra toward the low-luminosity far-infrared source IRAS 05405-0117 within the clump in the central part of Ori B9.

(Large APEX Bolometer Camera) at the APEX. The N2H⁺(1−0) and N2D⁺(2−1) spectral line observations toward the clump in the central part of Ori B9 have been performed with the IRAM 30 m telescope in Pico Veleta, Spain, in May 2007 (see Fig. 1). The total mass of gas and dust of the clump as derived from the dust continuum emission is ∼42 M⊙. Thus the clump has enough mass to form a small stellar group. This is also supported by the morphology of the clump, which is filamentary and fragmented into several cores. The relatively high degree of deuterium fractionation as derived from the N2D⁺ and N2H⁺ column density ratio, together with the physical properties of the cores within the clump indicate that they are low- to intermediate- mass star-forming cores. The ionization fraction in the cores, as derived using our previous H2D⁺ observations (Harju et al. 2006) together with the present observations, is in the range of about ∼ 10⁻⁹ < x(e) < 10⁻⁷ and they appear to be evolving quasi-staticly through the process of ambipolar diffusion.

2.2.2 Density distribution in molecular clouds Theoretical star formation scenarios predict the radial density distribution for a molecular cloud at the initial stage of the collapse of a cloud. The form of the density distribution is linked to the rate at which a protostar ac-

cretes mass from the surrounding envelope and further to the timescale of the collapse. It is thus an essen- tial factor considering the process of star formation. We have exploited the near-infrared color excess technique to study the radial density distributions of two cloud cores: we determine the mass distribution of a core that has very recently formed a star, and a core which is re- garded to be quiescent, close to hydrostatic equilibrium and thus possibly close to the initial stage of star formation. This study is based on near-infrared data taken with the ISAAC instrument on ESO’s VLT (Very Large Telescope). The two cores have significantly different radial density distributions; the core with star formation has a distribution well fitted with a single power-law, while the distribution of the core without star formation flattens at small radii. For the latter core, the distribution can be interpreted as the presence of significant additional support or very slow contraction.

2.2.3 Variations of far-infrared emissivity of dust particles

Recent observations have indicated that the far-IR emissivity (measured by the ratioτ(far-IR)/A^V) of dust particles in molecular clouds increases with decreasing temperature. Probable reasons for increased emissivity are coagulation of dust particles into large, fluffy aggregates and formation of ices on grain surfaces in dense regions.

We have combined ISO (Infrared Space Observatory) far-infrared observations with extinction measurements of the cloud L1642. We find that there is about a two- fold increase in emissivity when dust temperature de- creases from 19 K to 14 K. Our radiative transfer calculations show that, in order to explain the observed decrease of dust temperature towards the centre of L1642, an increase of emissivity of dust at far-IR is necessary.

This temperature decrease cannot be explained solely by the attenuation of interstellar radiation field.

2.2.4 High-latitude Hαclouds

Bright emission nebulae, or HII regions, around hot stars are readily seen in photographs. However, the all- pervasive faint Hαemission has only recently been detected and mapped over the whole sky. Mostly the Hα emission observed along a line of sight is produced by ionised gas in situ. There are, however, cases where all or most of the Hαradiation is due to scattering by elec- trons or dust particles which are illuminated by an Hα emitting source off the line of sight. We have shown that diffuse, translucent and dark dust clouds at high galactic latitudes are in many cases observed to have an excess of diffuse Hαsurface brightness, i.e. they are brighter than the surrounding sky. We have shown that the majority of this excess surface brightness can be understood as light

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scattered off the interstellar dust grains. The source of incident photons is the general Galactic Hαbackground radiation impinging on the dust clouds from all over the sky. (Mattila, Juvela and Lehtinen, 2007)

2.2.5 Scattered continuum radiation in interstellar and circumstellar clouds and in galaxies

Near-infrared scattered light was observed towards several interstellar clouds using ESO/NTT and UKIRT telescopes. In Corona Australis, part of the molecular cloud filament was mapped in three near-infrared bands. In accordance with previous theoretical predictions (Juvela et al. 2006), the observed surface brightness could be explained by light scattering. The near-infrared surface brightness was found to be an accurate tracer of cloud mass distribution. Therefore, observations of scattered light could become an important new method in studies of dense, quiescent clouds (Juvela et al. 2008). The study resulted in the publication of an ESO press release (ESO 06/08).

Near-infrared observations and the role of dust scattering was investigated also in connection with external galaxies. Numerical simulations indicated large uncertainty in the mass and mass spectrum of clouds detected with near-infrared observations (Kainulainen et al. 2007).

A separate study was conducted on the dust envelope of the carbon star IRC+10216, leading to new con- straints on the properties of the dust formed in stellar envelopes (Lunttila & Juvela 2007).

2.2.6 MHD phenomena: observations and modelling

We have successfully 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 by the group using surface temperature maps) and named on the basis of numerical modelling as ”active star Hale rule”. Spectroscopic observations 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 variability (cycles) in active late-type stars.

An important recent development is the magnetic inver- sions based on new spectropolarimetric data with up- graded spectropolarimeter and reduction software, giving the first observational proof for the theoretical pre- diction of magnetic field polarity.

The work is done in collaboration with astronomers in Potsdam, Germany and earlier with Uppsala, Swe- den, most of the collaborators originally having worked

in Helsinki Observatory and/or Oulu University.

Simultaneously to the observations, local and global MHD models (PENCIL-CODE, MEFISTO; Korpi, Käpylä, Lindborg) 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 development and validation of dynamo codes (Jouve et al. in press). Local turbulence models have been utilized to study the turbulent transport of angular momen- tum (Käpylä & Brandenburg 2007), and the importance of magnetic helicity conservation in laboratory (Bran- denburg & Käpylä 2007) and astrophysical settings have been studied (Brandenburg et al. 2007).

2.2.7 The Planck-satellite project

We participate in several science projects within the Planck Surveyor satellite project. The main emphasis is on studies of dense and cold parts of molecular clouds.

Simulations were carried out of the polarized emission of dust grains aligned in a magnetic field. The efficiency of radiative torques was investigated using magnetohydrodynamic cloud simulations and radiative transfer modelling. Predictions were made for future Planck observations (Pelkonen et al. 2007). 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 participate also in other Planck science projects, including one where Planck observations will be used for the study of nearby galaxies.

We coordinated a successful open time key program proposal for the Herschel satellite. The aim of that project is to use Herschel satellite for follow-up observations of a number of cold cloud cores detected in the Planck survey. The higher resolution of the Herschel instruments will be used to measure the internal structure of selected cores and to determine their relation with future star formation.

2.2.8 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 technique utilizes the

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difference between the spectra of the diffuse galactic scattered light (absorption line spectrum) and the EBL (pure continuum spectrum with possible discontinuities). For the spectroscopic observing program we have received 20 hours observing time at the ESO VLT/UT4 telescope, and the reductions and analysis of these data have been performed by Mattila and Lehtinen largely during 2007.

2.3 External financing and resources

The letters refer to project numbers in the following way:

a – 81525002, b – others)

2007: Person-months of work: 70^a, 35^b

Academy of Finland: 135 700 e^a, fellowship 54 000 e, research grants 82 000e

Private foundations 5 000e^a

2.4 Visits abroad

Haikala, Lauri

IRSF, South Africa, 7.–20.1.2007, 14 days ESO, La Silla Observatory, Chile, 31.1.–

16.2.2007, 17 days

ESO ALMA Day, Germany, 3.–7.9.2007, 5 days

MPIfR, Bonn, Germany, 18.– 20.9.2007, 3 days

ESO stc meeting; Garching, Germany, 22.–

25.10.2007, 3 days

NRO/NAOJ, Japan, 24.11.–3.12.2007, 10 days

UKIDSS, ESO, Garching, Germany, 16.–

19.12.2007, 4 days Harju, Jorma

European ALMA Science Advisory Commit- tee, ESO/Garching, Germany, 16.–17.4.2007, 2 days

Plack Consortium Meeting, Toulouse, France, 17.–21.6.2007, 5 days

ESO OPC Meeting, ESO/Garching, Ger- many, 22.–24.8.2007, 3 days

European ALMA Science Advisory Commit- tee, ESO/Garching, Germany, 18.–20.9.2007, 3 days

ESO OPC Meeting, ESO/Garching, Ger- many, 19.–22.11.2007, 3 days

Centre d’Etude Spatiale des Rayonnements, Toulouse, France, 2.–6.12.2007, 5 days

Juvela, Mika

Osservatorio Astrofisico di Catania (Planck galactic and solar system science work group meeting), Italy, 11.–18.1.2007, 6 days

ESA/ESTEC (Herschel open time key programme workshop), The Netherlands, 19.–

22.2.2007, 3 days

Nordita, Stockholm (New Trends in Radiation Hydrodynamics, workshop), Sweden, 9.–11.5.2007, 3 days

ESO, Garching (OPC meeting), Germany, 21.–25.5.2007, 4 days

CESR, Toulouse (Planck Consortium meeting), France, 17.–21.6.2007, 4 days

KAVLI, Santa Barbara (Star formation through cosmic time, workshop), USA, 3.–

30.9.2007, 28 days

Physikalisches Institut Universit¨at zu K¨oln (FIR2007 meeting), Germany, 4.–8.11.2007, 5 days ESO, Garching (OPC meeting), Germany, 18.–23.11.2007, 5 days

Ecole Normal Superieure, Lyon (Viva voce), France, 29.11.–1.12.2007, 2 days

Kainulainen, Jouni

Calar Alto observatory, Spain, 6.–16.2.2007, 11 days

K¨apyl¨a, Petri

XLI Annual Conference of the Finnish Physi- cal Society, 15.–17.3.2007, Tallinn, Estonia, 3 days NORDITA/Stockholm University (Workshop:

New Trends in Radiation Hydrodynamics), 9.–

11.5.2007, 3 days

Astrophysicalisches Institut Potsdam (5th Potsdam Thinkshop: Meridional flow, differential rotation, solar and stellar activity), Germany, 24.–

29.6, 5 days

NORDITA (Pencil Code User Meeting), Stockholm, Sweden, 19.–20.7.2007, 2 days

Kiepenheuer–Institut f¨ur Sonnenphysik, Freiburg, Germany, 18.–20.9, 3 days

Institute for Theoretical Physics (ASTROSIM steering committee meeting), Z¨urich, Switzerland, 21.9, 1 day

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Korpi, Maarit

XLI Annual Conference of the Finnish Physi- cal Society, 15.–17.3.2007, Tallinn, Estonia, 3 days NORDITA, Stockholm, Sweden, 19.- 21.4.2007, 3 days

Lehtinen, Kimmo K.

UKIDSS, ESO, Garching, Germany, 16.–

20.12.2007, 5 days Liljestr¨om, Anne

Queen’s University, Belfast, U.K., 3.–6.1.2007, 4 days

XLI Annual Conference of the Finnish Physi- cal Society, 15.–17.3.2007, Tallinn, Estonia, 3 days NORDITA, Stockholm, Sweden, 19.–

21.4.2007, 3 days

Pencil Code User Meeting; NORDITA, Stock- holm, Sweden, 19.–20.7.2007, 2 days

Mattila, Kalevi

ESO Committee of Council, Potsdam, Ger- many, 19.–20.3.2007, 2 days

European Southern Observatory, ESO Coun- cil, Garching, Germany, 5.–6.6.2007, 2 days

European Southern Observatory, ESO Com- mittee of Council, Oxford, U.K., 1.–2.10.2007, 2 days

European Southern Observatory, ESO Coun- cil, Garching, Germany, 4.–5.12.2007, 2 days

European ALMA day, Garching, Germany, 3.–5.9.2007, 3 days

Miettinen, Oskari

Observations with IRAM:in 30-m radio telescope, Granada (Pico Veleta), Spain, 17.–

20.5.2007, 4 days

”Massive Star Formation: Observations Con- front Theory” Conference, Heidelberg, Germany, 9.–14.9.2007, 6 days

Pelkonen, Veli–Matti

Planck WG 2 ja WG 7 meeting, Catania, Italy, 11.–18.1.2007, 8 days

ESO observatorio La Silla, Chile, 1.–

13.6.2006, 13 days

Planck consortium meeting, Toulouse, France, 17.–22.6.2007, 6 days

4. Spitzer meeting (The Evolving ISM in the Milky Way and Nearby Galaxies), USA, 1.–

8.12.2007, 8 days

Tuominen, Ilkka

Astronomy & Astrophysics Journal, board of directors meeting, Wien, Austria, 4.–5.5.2007, 2 days

5th Potsdam Thinkshop: Meridional flow, differential rotation, solar and stellar activity, Ger- many, 24.–29.6.2007, 7 days

MHD laboratory experiments for geophysics and astrophysics, Catania, Italy, 29.9.–4.10.2007, 7 days

2.5 Papers read at scientific conferences, symposia, meetings etc.

Harju, Jorma

”H2D+ – a tool for interpreting Planck data on cold cores”, Planck Consortium Meeting, 17.–

21.6.2007, Toulouse, France, poster Juvela, Mika

”Cold cores”, Planck galactic and solar system science work group meeting, 15.1.2007, Catania, Italy, invited talk

”Cold cores – a proposal for a Herschel open time key programme”, Herschel open time key programme workshop, 19.–21.2.2007, ESTEC/ESA, The Netherlands

”Radiation transfer in molecular clouds”, New Trends in Radiation Hydrodynamics, 10.5.2007, Nordita, Sweden, invited talk

”Radiative transfer modelling of interstellar clouds”, seminar series, 25.5.2007, Munich Univer- sity Observatory, Germany, invited talk

”Cold cores”, Planck Consortium meeting, 19.6.2007, Toulouse (CESR), France, invited talk

”Galactic Cold Cores”, Star formation through cosmic time, workshop, 24.9.2007, Kavli, Santa Barbara, CA, USA, invited talk

”Modelling polarized radiation from interstellar clouds”, FIR 2007: Far-infrared and sub- millimeter emission of the interstellar medium, 5.–7.11.2007, Bad Honnef (Physikalisches Institut Universit¨at zu K¨oln), Germany, poster

K¨apyl¨a, Petri

”α-effect and turbulent pumping from local 3D convection models”, XLI Annual Conference of the Finnish Physical Society, 15.–17.3.2007, Tal- linn, Estonia, talk

”Turbulent viscosity and Λ-effect from numerical turbulence models”, 5th Potsdam Thinkshop:

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Meridional flow, differential rotation, solar and stellar activity, 24.-29.6.2007, Potsdam, Germany, talk

”High resolution MHD calculations on the Finnish Louhi machine”, Pencil- Code User Meet- ing 2007, 15.8.2007, Stockholm, Sweden, talk Korpi, Maarit

”Kinematic frames and active longitudes:

Does the Sun have a face?”, XLI Annual Confer- ence of the Finnish Physical Society, 15.–17.3.2007, Tallinn, Estonia, poster

Liljestr¨om, Anne

”On the Ratio of the Maxwell to Reynolds Stresses in MRI-active Protostellar Disks”, XLI Annual Conference of the Finnish Physical Soci- ety, 15.–17.3.2007, Tallinn, Estonia

”Predicting turbulent stresses in MRI active disks”, Suomen t¨ahtitieteilij¨aseura ry (Finnish Astronomical Association): Astronomers’ Day, 1.6.2007, Tuorla, Finland

”Reynold stresses in shearing boxes”, Pencil Code User Meeting 2007, 15.8.2007, Stockholm, Sweden

Mattila, Kalevi

”Kolme vuotta ESO-j¨asenyytt¨a” (”Three years of ESO membership”), The XI Meeting of Finnish National COSPAR (FinCOSPAR), 4.–

5.10.2007, Espoo, Finland, invited talk Miettinen, Oskari

”SiO and CH3CCH abundances and dust emission in high-mass star-forming cores”, Mas- sive Star Formation: Observations Confront The- ory, 9.–14.9.2007, Heidelberg, Germany, poster Pelkonen, Veli–Matti

”Radiative transfer modelling of clouds and cores”, FIR Workshop 2007, 5.–7.11.2007, Physikzentrum, Bad Honnef, Germany, poster

”Two views on dust: polarized thermal dust emission and near-infrared scattering”, 4th Spitzer Science Center Conference: The Evolving ISM in the Milky Way and Nearby Galaxies, 2.–5.12.2007, Hotel Hilton, Pasadena, Kalifornia, USA, poster Ridderstad, Marianna

”3D Modeling of the High-Latitude Cloud L1780”, The XI Meeting of Finnish National COSPAR (FinCOSPAR), 4.–5.10.2007, Espoo, Finland, poster

”Teaching & public outreach in the field of astrobiology: Finland as an example”, EANA 2007 – 7th European Astrobiology Workshop, 21.–

24.10.2007, Turku, Finland, poster

2.6 Visiting academics

Harju, Jorma

Hotzel, Stephan, PhD, J¨org Gmbh, Germany, 13.–27.3.2007, 15 days

Hieret, Carolin, Dipl.Phys., Max-Planck- Institut f¨ur Radioastronomie, Bonn, Germany, 11.–17.3.2007, 7 days

Juvela, Mika

Collins, David, MSc, CASS/UCSD, USA, 1.–

16.7.2007, 15 days

Ristorcelli, Isabelle, PhD, CESR/CNRS-UPS, Toulouse, France, 8.–10.10.2007, 3 days

Montier, Ludovic, PhD, CESR/CNRS-UPS, Toulouse, France, 8.–10.10.2007, 3 days

Korpi, Maarit

K¨apyl¨a, Petri, FT, Nordita, Sweden, 19.–

30.03.2007; 14.–16.11.2007, 14 days Mattila, Kalevi

Lemke, Dietrich, Prof., MPI Astronomie, Ger- many, 30.5.–8.6.2007, 10 days

Leinert, Christoph, Prof., MPI Astronomie, Germany, 18.–26.6.2007, 9 days

Hennemann, Martin, Dipl. Phys., MPI As- tronomie, Germany, 19.11.–26.6.2007, 29 days

Goncalves, Jos, PhD, University of Lissabon, Portugal, 1.10.–23.12.2007, 90 days

Rawlings, Mark, PhD, Joint Astronomy Centre, Hawaii, USA, 29.9.–8.10.2007; 25.11.–

3.12.2007, 18 days

V¨ais¨anen, Petri, FT, South African As- tronomical Observatory, South Africa, 27.11.–

4.12.2007, 8 days

2.7 Acting as Opponent and pre- examinations of doctoral disser- tations

Juvela, Mika

Jaime Forero-Romero: ”Applications de l’approche hybride – predictabilit´e, galaxies in- frarouges et lentilles gravitationelles”, Ecole normal superieure, Lyon, 30.11.2007, France, opponent

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2.8 Membership in scientific and schol- arly societies

Haikala, Lauri

ESO Scientific technical committee, 2007, Germany, expert

Harju, Jorma

European ALMA Science Advisory Commit- tee, 1.1.–31.12.2007

ESO OPC LABOCA Special Panel, 1.–

24.8.2007

ESO OPC Panel C – ’Interstellar Medium, Star Formation and Planetary Systems’, 1.11.2007–29.5.2008

Finnish National Committee of URSI, 1.1.–

31.12.2007, Finland Juvela, Mika

The organizing committee of IAU Division VI, Interstellar Matter, 1.1.–31.12.2007, USA

Steering committee of the project AS- TROSIM, European Science Foundation, 1.1.–

31.12.2007, France

European Southern Observatory, panel member in Observing Programmes Committee, 25.1.2007–, Germany, expert

European Southern Observatory, member in Observing Programmes Committee, 6.9.2007–, Germany, expert

Planck satellite consortium, coordinator in two technical and a scientific working group Mattila, Kalevi

ISO/ISOPHOT Consortium, 1991–

Planck LFI, 1998–

Finnish National Committee for Astronomy, 1973–, Finland

Finnish National Committee for Astronomy, 14.8.2007–, Finland, chair

Odin Science Team, 1991–

European Southern Observatory, Council

Ridderstad, Marianna

Finnish Astrobiology Network, 2006–, Finland Tuominen, Ilkka

Finnish National Committee for Astronomy (IAU), 1.1.–13.8.2007, Finland, chair; board member 14.8.2007–

Astronomy & Astrophysics Board of Direc- tors, France

2.9 Refereeing and Other Publishing Activities

Harju, Jorma

Astrophysical Journal, 7.–29.3.2007; 13.–

27.7.2007, referee

Astronomy & Astrophysics, 12.–31.12.2007, referee

Juvela, Mika

Astronomy & Astrophysics, France, referee Astrophysical Journal, 22.8.–11.9., 19.–28.11., 21.12.; 5.–16.4.2007, USA, referee

Astrophysical Journal Letters, 27.12.2007–, USA, referee

K¨apyl¨a, Petri

Astronomische Nachrichten, Germany, referee Mattila, Kalevi

Astronomy and Astrophysics, 1.1.–31.12.2007, France, referee

Astrophysical Journal, 1.1.–31.12.2007, USA, referee

Monthly Notices of the R.A.S., 1.1.–

31.12.2007, U.K., referee Tuominen, Ilkka

Astronomy & Astrophysics, France, referee

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3 High Energy Astrophysics

Project number 91525005

Research agreements Academy of Finland Tekes

ESA

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

Telephone 19122948

Fax 19122952

E-mail Juhani.Huovelin@Helsinki.Fi Senior (Ph.D. or higher) Diana Hannikainen, Docent

Juhani Huovelin, Docent Thomas Hackman, Ph.D.

Jukka Nevalainen, docent Ph.D. student(s) Lauri Alha, M.Sc.(Tech.) Kristiina Byckling, M.Sc.

Linnea Hjalmarsdotter, M.Sc.

Tuomas Lehto, M.Sc.

Sami Maisala, M.Sc.

Tero Oittinen, M.Sc.

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

Jukka-Pekka Saarikko , M.Sc.

(Dept. of Physical Sciences) Mikko Väänänen. M.Sc.

Students Jussi Ahoranta

Eero Esko Jasmin Haikonen Karri Koljonen Tuure Takala Minttu Uunila

Associated scientists Pasi Hakala, docent (Turku)

3.1 General approach

The activities of high energy astrophysics research of HESA (High Energy Space Astronomy) are divided into three areas, fundamental science, developing of new instruments for space research, and developing of science data analysis software.

The first part consists of scientific return (guaranteed time) from the instrument projects (INTEGRAL, SMART-1), complemented by data from other satellites (e.g. XMM-Newton, HST, RXTE, Chandra). The second part is a continuation to the ongoing hardware projects including research also in detector physics. The science topics addressed include accretion discs and su- perorbital periods of Low Mass X-ray Binaries, multifrequency behaviour of Microquasars, coronae and flaring in active stars and the Sun. In particular, the very broad spectral coverage (INTEGRAL and the AGN- collaboration) and the possibility for a very long moni- toring (SMART-1 cruise phase), coupled to the sophis- ticated modelling, are the key ingredients of the science programme.

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 advances in instrument performances carried along with bigger telescopes, larger field-of-view and decreased noise of new systems in the future plans

of ESA (XEUS,LOBSTER). The specific improvements which are meaningful are: 1) the huge enhancement of sensitivity and spectral resolution with XEUS, which en- ables studies of X-ray spectra of Galactic sources with the same quality we nowadays can investigate the solar 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 on- board software of SIXS and MIXS instruments for Bepi- Colombo (3) new PowerPC based DPU board for future space missions, like XEUS, (4) the XSM solar monitor for ISRO’s (India) Chandrayaan-1 Moon mission, and, (5) ESO Reflex software.

The activities of HESA have resulted in the com- pletion of three space science instruments, and a successful launch of INTEGRAL and SMART-1 missions with our working hardware onboard. The scientific use of INTEGRAL has already resulted in a number of scientific papers published in 2003-5. SMART-1/XSM has made effective observations of the Sun from March 2004 to August 2006. Several 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 preparation. At present, the scientific utilization of INTEGRAL and SMART-1 contin- ues.

SMART-1 mission was terminated in September 2006. Observation programs with other satellites (RXTE, XMM-Newton, Chandra) and ground-based telescopes (e.g. NOT, ESO, ATCA), 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 technological 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, i.e. BepiColombo. We are also involved at PI level in the India-ESA collaborative Moon mission Chandaryaan-1 (launch in 2008) with an XSM similar to that of SMART-1, and newly emerged (2005) collaborative plan Spectrum-X-Gamma/EROSITA/Lobster of ESA and Russia (launch in 2012-13) with GEM-based detectors for Lobster and possibly also for the Russian X-ray telescopes. The in-kind contribution of Finland’s joining fee to ESO was completed successfully by the Finnish Sampo project.

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3.2 Science topics

3.2.1 Interacting compact binaries

The main aims of this research program are to study X- ray binaries in novel ways. X-ray binaries are systems in which a compact primary (black hole, neutron star, or in the case of cataclysmic variables, white dwarf) accretes matter from a non-degenerate companion. This matter swirls around the compact object in an accretion disk the accretion disk is the main source of X-ray radiation from X-ray binaries. X-ray binaries radiate at all wavelengths, from the radio to the hard X-rays.

One aim of this research program is to study the numbers, structure and evolution of very short period binary systems. These systems consist of a degenerate primary star and a mass-losing secondary component that in the ultra-short period systems is either a white dwarf or a helium star. In systems with periods above about 80 minutes the donor can also be a main sequence star.

These systems are also the main source of gravitational radiation to be measured for the first time by some future mission like ESAs and NASAs joint project LISA. These systems are crucial in verifying the theory of general relativity. We also intend to continue developing new data modeling techniques for accretion process studies (i.e. probing the structure and shape of accretion disks).

These include combining Doppler tomography of disks with lightcurve modeling.

Another important aspect of this research program is to disentangle and thus decipher the high energy spectra of accreting low mass X-ray binaries. This is done through a truly physical (as opposed to largely phe- nomenological) model and observations from e.g. IN- TEGRAL where our group is a Co-I team and major radio telescopes. We expect to explain many of the phenomena related to accretion the acc retion disk, a corona (or pl asma cloud) sur rounding the central parts of the accretion disk (and hence the compact accretor which is usually a black hole), and possible outflows seen as bipolar jets in the case of microquasars.

To summarize, the aims of our project are threefold.

We observe ultrashort binaries which are essentially test laboratories of general relativity and gravitation. We will use various tomographic methods in order to resolve disk structure and dynamics. We shall study the high energy processes in X-ray binaries containing black holes to resolve jet launching mechanisms and jet-disk-corona interactions.

3.2.2 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. 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 ener- getic 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 temperature of the ionized gas (plasma).

Our research aims at clarifying the physical mecha- nism of the eruptions by examining the X-ray spectrum and its variation 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 is expected from by a Finnish solar monitor on the Indian Chandrayaan-1 mission (launch scheduled in 2008), and later, especially, with the Finnish solar monitor SIXS on ESA’s BepiColombo (launch August 2013), both of which are projects lead by the HESA group.

The data will enable obtaining a thorough new in- sight in understanding 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 modeling the X-ray spectra of other stars, with the aim of understanding their coronae.

3.2.3 Clusters of galaxies

Our research aims in characterizing thermal and non- thermal processes in the clusters of galaxies. We examine and utilize the hydrostatic equilibrium of cluster material and use it to derive baryonic and dark matter density distributions. We use this information to con- strain cosmological parameters (e.g. Sadat et al, 2005).

We also examine the ”soft X-ray excess” component in clusters (e.g. Bonamente et al. 2005).

The main obsevational tools utilized by us are high resolution imaging and spatially resolved spectroscopy of the X-ray emission of the hot intracluster gas. We carry out analysis of the cluster data obtained with XMM-Newton and Chandra X-ray satellites. The total cluster mass determination within the virial radius

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is a complicated task because the cluster brightness de- creases rapidly with the radius. Both XMM-Newton and Chanda suffer from Solar particle induced flaring background which renders the background modeling uncer- tain. These uncertainties, if not properly accounted for, reduce the accuracy of the measurement of cluster temperature and consequently the total masses.

In order to examine the background stability, we carried out a systematic study of a sample of XMM-Newton blank sky observations (Nevalainen et al, 2005). We developed a double-filtering method,which reduces the background uncertainties significantly, compared to the commonly used method. By comparing the background estimate with the blank sky data we evaluated the involved uncertainties and presented a practical method to propagate the uncertainties when measuring cluster temperatures. Our work is acknowledged by the XMM- Newton telescope team who advertise our background method in their web site.

3.3 The ESO-Sampo project

ESO-connected activities have also begun effectively since the beginning of Finlands membership in 2004.

HESA group leads the University of Helsinki share of the Finnish in-kind project for partial payment of the entrance fee to ESO. The project, called ESO-Sampo, conducts development of science data analysis environment for ESO. Four IT professionals works full time for the in-kind contribution in the period 1.1.2005- 31.1.2008 in a Tekes-funded project at the Observatory, Univer- sity of Helsinki. The main result of the project was the ESO Reflex workflow engine, an advanced science analysis environment which ESO will implement in 2008 as standard ESO software for the reduction of VLT and other ESO data.

The Observatory has also participated actively in the preparation of national technology return from ESO.

These have already lead to a request from ESO to continue ESO Reflex development by partial ESO funding in 2008. Other activities arosen from this are proposals to Tekes for (1) development of a multidisciplinary knowledge discovery system, and (2) another similar application for security systems.

3.4 External financing and resources

2007: Man-months of work: 160 Academy of Finland: 239 000 e

National Technology Agency: 2 399 000e European Space Agency: 100 000e Foundations: 6 000e

3.5 Tests of learning

Kajatkari, Perttu

M.Sc.-thesis: ULX M82 X-1: spectral and lightcurve analysis; 2007; University of Helsinki, Department of Astronomy

Mynttinen, Johanna

M.Sc.-thesis: GRS 1015+105: a spectral study of different classes observed with INTE- GRAL; 2007; University of Helsinki, Department of Astronomy

Savolainen, Petri

M.Sc.-thesis: Modelling the X-ray spectrum of the neutron star LMXB GX 9+9; 2007; University of Helsinki, Department of Astronomy

Uunila, Minttu

M.Sc.-thesis: Investigations of particle detection capability of the XSM om SMART-1; 2007;

University of Helsinki, Department of Astronomy

3.6 Visits abroad

Hannikainen, Diana

University of Sydney, School of Physics, Aus- tralia, 27.2.–22.3.2007, 23 days

University of Grenoble, Laboratoire d’Astrophysique de l’Observatoire de Greno- ble, France, 25.–27.4.2007, 3 days

Southampton, Department of Physics and As- tronomy, U.K., 10.–13.5.2007, 4 days

ESO, Germany, 21.–24.5.2007, 4 days

Laboratori Nazionali di Frascati, INAF, Italy, 27.5.–3.6.2007, 8 days

Physikalisches Institut, Friedrich-Alexander- Universit¨at, Germany, 22.–26.7.2007, 5 days

Yerevan State University, Armenia, 19.–

25.8.2007, 7 days

Service d’Astrophysique, CEA Saclay, France, 20.–27.9.2007, 8 days

INAF – Istituto di astrofisica spaziale e fisica cosmica, Italy, 16.–19.10.2007, 4 days

Mullard Space Science Laboratory, UCL, U.K., 24.–27.10.2007, 4 days

University of Florida, USA, 27.10.–2.11.2007, 7 days

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Huovelin, Juhani

XLI Annual Conference of the Finnish Physi- cal Society, 15.–17.3.2007, Tallinn, Estonia, 3 days BepiColombo SIXS ISRR meeting, ESTEC;

Noordwijk, The Netherlands, 14.–15.5.2007, 2 days ESO-Sampo meeting, Garching, Germany, 31.5.2007, 1 day

BepiColombo SWG meeting, ESTEC, Noord- wijk, The Netherlands, 25.–26.6.2007, 2 days

Meeting with ESO Director General, ESO, Garching, Germany, 16.11.2007, 1 day

Sampo project meeting, ESO, Garching, Ger- many, 7.12.2007, 1 day

BepiColombo SWT4 meeting, Germany, 18.–

19.9.2007, 2 days Maisala, Sami

ESO Reflex workshop; Garching, Germany, 22.–23.1.2007, 2 days

ESO/Sampo meetings, Garching, Germany, 12.–16.3.2007, 5 days

Sampo team meeting, Garching, Germany, 15.–16.5.2007, 2 days

Sampo team meeting; Garching, Germany, 29.5.–1.6.2007, 4 days

ADASS 2007, London, U.K., 23.–28.9.2007, 6 days

Sampo project meeting, ESO, Garching, Ger- many, 6.–8.12.2007, 3 days

Nevalainen, Jukka

University of Heidelberg, Germany, 30.3.–

3.4.2007, 2 days

University of California, LA, USA, 9.–

11.5.2007, 3 days

International Space Science Institute, Switzer- land, 17.–21.6.2007, 5 days

Universit Paris Sud, Orsay, France, 14.–

15.12.2007, 2 days

Meeting at Tartu, Toravere, Estonia, 25.–

28.2.2007, 4 days Oittinen, Tero

VOTech meeting ESO, Garching, Germany, 12.–18.3.2007, 7 days

Sampo Team Meeting; Garching, Germany, 15.–16.5.2007, 2 days

ESO Team Meeting; Garching, Germany, 29.–

31.5.2007, 3 days

ADASS 2007, London, U.K., 23.–28.9.2007, 6 days

TechNet Europe 2007, Sweden, 16.–

18.10.2007, 3 days

Sampo project meeting; ESO, Garching, Ger- many, 6.–8.12.2007, 3 days

Solin, Otto

ESO/Sampo Reflex Workshop, Germany, 22.–

23.1.2007, 2 days

ESO/Sampo project meetings; Garching, Ger- many, 12.–16.3.2007, 5 days

Sampo project visit to ESO headquarters;

Garching, Germany, 6.5.–1.6.2007, 27 days ADASS 2007, London, U.K., 23.–28.9.2007, 6 days

Sampo project meeting; ESO, Garching, Ger- many, 6.–9.12.2007, 4 days

Somero, Auni

3rd Workshop for Nordic Network for Women in Physics, Technical University of Denmark, Den- mark, 14.–19.8.2007, 6 days

Ullgren, Marko

Opticon N3.6 network face-to-face meeting, Tenerife, Spain, 1.–2.3.2007, 2 days

Sampo team meeting, Germany, 30.–

31.5.2007, 2 days Väänänen, Mikko

7th RHESSI Workshop, Santa Cruz, USA, 24.6.–1.7.2007, 12 days

3.7 Papers read at scientific conferences, symposia, meetings etc.

Hannikainen, Diana

”Multifrequency observations of microquasars”, Multifrequency Behaviour of High Energy Cosmic Sources, 27.5.–3.6.2007, Vulcano, Italy, invited talk

”X-ray properties of microquasars”, Joint Eu- ropean and National Astronomy Meeting; High Energy Astrophysics: the keV-TeV connection, 19.–25.8.2007, Yerevan, Armenia, invited talk

”GRS 1915+105: Snapshots with INTE- GRAL”, conference A Population Explosion: The nature and evolution of X-ray binaries in diverse

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environments, 27.10.–2.11.2007, St. Petersburg, Florida, USA, poster

”Synchrotron flaring behaviour of Cygnus X- 3”, A Population Explosion: The nature and evolution of X-ray binaries in diverse environments, 27.10.–2.11.2007, St. Petersburg, Florida, USA, poster

”RXTE and INTEGRAL observations of IGR J19140+0951”, A Population Explosion: The nature and evolution of X-ray binaries in diverse environments, 27.10.–2.11.2007, St. Petersburg, Florida, USA, poster

Maisala, Sami

”Using ESO Reflex with Web Services”, ADASS XVII, 23.–28.9.2007, London, U.K., poster

”ESO Reflex: A Graphical Workflow Engine for Data Reduction”, ADASS XVII, 23.–28.9.2007, London, U.K., poster

Oittinen, Tero

”Using ESO Reflex with Web Services”, ADASS XVII, 23.–28.9.2007, London, U.K., poster

”ESO Reflex: A Graphical Workflow Engine for Data Reduction”, ADASS XVII, 23.–28.9.2007, London, U.K., poster

Ullgren, Marko

”ESO Reflex: A Graphical Workflow Engine for Data Reduction”, ADASS 2007, 23.–26.9.2007, London, U.K., poster

”Using ESO Reflex with Web Services”, ADASS 2007, 23.–26.9.2007, London, U.K., poster

3.8 Membership in scientific and schol- arly societies

Hannikainen, Diana

International Workshop on Radiation Imaging Detectors, expert

ESO Observing Proposal Committee, May &

November 2007, expert

Huovelin, Juhani

Finnish COSPAR committee, Finland Research school for astronomy and astrophysics, Finland

Tuorla Observatory board, Finland

Academy of Finland assessor pool, Finland, expert

Nevalainen, Jukka

XMM-Newton AO7 Time Allocation Commit- tee, 12.–14.11.2007, U.K., expert

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

3.9 Acting as Opponent and pre- examinations of doctoral disser- tations

Hannikainen, Diana

Clement Cabanac: ”Variabilite temporelle des binairesX: observations avec INTEGRAL. Modeli- sation”, University of Grenoble, 26.4.2007, France, opponent

Fiamma Capitanio, University of Southamp- ton, 11.5.2007, U.K., opponent

3.10 Refereeing and Other Publishing Activities

Hannikainen, Diana

Monthly Notices of the Royal Astronomical Society, March 2007, U.K., referee

Nuclear Instruments and Methods in Physics Research, referee

Huovelin, Juhani

Earth and Planetary Science, Japan, referee Nevalainen, Jukka

Publications of the Astronomical Society of Japan, October 2007, referee

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4 Planetary System Research

Project number 02525008

Research agreements Academy of Finland Type of research Basic research

Director of research DocentMuinonen, Karri

Telephone 19122941

Fax 19122952

E-mail Karri.Muinonen@Helsinki.Fi

Research staff with a Ph.D. Karri Muinonen, Docent Kari Lumme, Prof Phd student(s) Mikael Granvik, M.Sc.

Jyri N¨ar¨anen, M.Sc.

Dagmara Oszkiewicz, M.Sc.

Hannu Parviainen, M.Sc.

Antti Penttil¨a, M.Sc.

Jari Rantala, M.Sc.

Johanna Torppa, M.Sc.

Jani Tyynel¨a, M.Sc.

Students Jarkko Niemel¨a

Hannakaisa Erkkil¨a Associated scientists Markku Poutanen, Prof.

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

4.1 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 focussed 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. Ex- periments have been carried out to measure backscattering characteristics of particulate media (scatterometer at the Observatory) and to assess the X-ray fluorescence by planetary-regolith analog samples (at the Department of Physical Sciences). 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 and their detailed interpretation is in progress.

Systematic light-scattering simulations have been carried out for Gaussian-random-sphere particles with the Discrete-Dipole Approximation (DDA, Muinonen et al. 2007B1). These simulations have allowed PSR researchers to unveil the single-scattering in- terference mechanisms for the enhanced-intensity and negative-polarization branches of wavelength-scale scat-

terers (Muinonen et al. 2007B1, Tyynel¨a et al. 2007B1).

The mechanisms have been studied in detail for spherical particles by concentrating on the properties of the electromagnetic fields inside the scatterers. First steps have been taken to assess the properties of the internal fields of Gaussian particles (Tyynel¨a et al. 2007B2). Fur- thermore, DDA has been utilized to search for coherent- backscattering effects (Penttil¨a and Lumme 2007B2).

Understanding the physical mechanisms of the backscattering phenomena is of utmost importance, for example, for remote investigations of the solar system.

Figure 2: Shape model of asteroid (1862) Apollo from two perpendicular equatorial viewing directions.

Lightcurve inversion was performed using the convex inversion method and all the available lightcurve data.

In scattering of light by single small particles, PSR has studied surface-roughness effects using the DDA method and the Gaussian-random-sphere geometry, fo- cusing on both harmonic roughness and what can be called ”ragged” roughness (Nousiainen and Muinonen 2007B1, Zubko et al. 2007B1). Scattering by thin ir- regularly undulating films has also been studied using DDA (Parviainen and Lumme 2007B2). PSR has de-

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veloped a possible way to generate concave hulls on concave shapes, with application to light scattering by concave-hull-transformed Gaussian particles (Muinonen and Erkkilä 2007B2). In scattering of light by particulate media, surface-roughness effects are being incorpo- rated into both scattering and X-ray fluorescence models for planetary regoliths using fractional-Brownian- motion surfaces and size distributions of spherical particles (Parviainen and Muinonen 2007B1, Näränen et al.

2007B2a, N¨ar¨anen et al. 2007B2b).

Figure 3: Possible spin-axis directions of asteroid (31) Euphrosyne. Lightcurve inversion was performed using the convex inversion method and all the available lightcurve data.

Detailed comparisons have been carried out between different DDA codes (Penttil¨a et al. 2007B1). Radar backscattering by shoots of scots pines have been studied using DDA (Manninen et al. 2007B1). As light scattering has also direct applications in industrial processes, PSR has continued to model some industrial products like paper coatings for ideal light scattering. One of the purposes is to improve the quality of paper.

PSR has continued studies of light scattering by large irregular Saharan sand particles, via Gaussian- random-sphere modelling for their shapes and assessing the significance of surface-roughness effects on scattering (Munoz et al. 2007B1, Munoz et al. 2007B2). Light scattering by such particles has been revisited both ex- perimentally and theoretically: particle scattering characteristics are seen to be dictated by small-scale surface roughness.

In the field of asteroid orbital inversion using statistical methods, PSR has succeeded in finalizing orbital inverse methods for arbitrary numbers of observations and arbitrary observational time intervals. Recent de- velopments include, e.g., the n-body statistical ranging (Granvik and Muinonen 2007B2).

Figure 4: The layout of the goniometric laboratory setup used to study the regolith effects on X-ray fluorescence spectroscopy. Both emergence and incidence angles can be varied to simulate realistic observation geometries from orbiting spacecraft, e.g. ESA BepiColombo mission to Mercury. The measurements need to be performed in vacuum since air in NTP conditions is an efficient ab- sorber and scatterer of soft X-rays.

PSR has assessed the asteroid identification problem at discovery as well as across multiple apparitions and derived efficient loglinear identification methods based on augmented red-black binary trees and dimensionality- reduction techniques (Granvik 2007A1, Granvik et al.

Figure 5: An image of the goniometric laboratory setup used to study the regolith effects on X-ray fluorescence spectroscopy. Both emergence and incidence angles can be varied to simulate realistic observation geometries from orbiting spacecraft, e.g., ESA BepiColombo mission to Mercury. The measurements need to be performed in vacuum since air in NTP conditions is an efficient ab- sorber and scatterer of soft X-rays.

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2007B1). The new identification methods have been successfully applied, first, to observational data obtained nearly simultaneously with the ESO/VLT (Very Large Telescope) and CFHT (Canada-France-Hawaii Telescope) groundbased telescopes as well as the Spitzer space observatory (Granvik et al. 2007B1) and, second, to single-apparition observational data collected during the last hundred years or so (Granvik and Muinonen 2007B2). Granvik et al. (2007) successfully applied the short-term identification method to astrometric observations obtained nearly-simultaneously with the Canada- France-Hawaii Telescope, ESO’s Very Large Telescope, and the Spitzer space telescope. In addition to solv- ing the nontrivial identification problem, they derived an empirical rule-of-thumb for the decrease in orbital- element uncertainty obtained via stereoscopic observations as compared to a single-telescope approach.

Figure 6: Typical soft X-ray fluorescence spectrum of olivine basalt (lunar mare regolith analog), as measured with the soft X-ray spectrogoniometer. The sample is excited by a Titanium anode X-ray tube, and the energy range in this spectrum is 3.1-8.0 keV. The crosses are the measured spectrum and the line is the empirical multiple-Gaussian model, which fits well all the mea- surable elemental fluorescence emission lines from the sample.

Lightcurve inversion for asteroid spins and shapes has progressed steadily using the convex inversion methods (Torppa 2007A1). At the Nordic Optical Tele- scope (NOT), PSR has coordinated a major Nordic NEON (Near-Earth-Object Network) photometric and astrometric observing program on near-Earth objects (NEOs). The observations have been interpreted using statistical convex-inversion techniques as well as analyti- cal techniques using simple shape models such as sphere- cylinders (Muinonen et al. 2007B2). As an important

Figure 7: A scanning-electron-microscope image of olivine basalt sample with particle-size range of 75-250 micrometers. This sample is considered to be a good analog material for lunar mare regoliths and has been used by PSR in laboratory investigations of viewing- geometry-dependent effects in both visible and soft X- ray wavelengths. The scale bar in the bottom left corner of the image indicates a length of 200 micrometers in the image.

step toward statistical asteroid spin and shape inversion methods, a downhill simplex inversion method has been established for general convex shape models (Muinonen and Torppa 2007B2). PSR participation in observing programs has resulted in publication of NEO astrometric positions (Muinonen et al. 2007B3a and 2007B3b) as well as Minor Planet Electronic Circular (MPEC) on comet 19P/Borrelly (Bagnulo et al. 2007B3).

PSR is actively participating in the interpretation of the AMIE camera observations of the Moon (Josset et al. 2007B2). SMART-1 was launched in 2003 and the mission ended with an impact of the spacecraft on the lunar surface in 2006. During the extended mission phase, upon request by PSR, AMIE observations of the Moon were carried out close to opposition geometries. The calibration of the AMIE image data started in late 2007, providing good prospects for quantitative interpretation of the extensive lunar image data (more than 100 000 images taken).

PSR is a key participant in the BepiColombo mission to Mercury (launch in 2013): Mercury Imaging X-ray Spectrometer MIXS (UK PI, Finnish Co-PI) will carry out a global elemental and surface-structural mapping of Mercury, whereas the Solar Intensity X-ray and particle Spectrometer SIXS (Finnish PI, UK Co-PI) will provide the simultaneous calibration observations of the flux of radiation and particles. In preparation for BepiColombo,

Department of Astronomy Annual Report 2007

Observatory

University of Helsinki Annual Report 2007

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

Foreword

Contents

1 Strategy of the Observatory

2 Interstellar medium, star for- mation and magnetic activity of stars

2.1 Research activities

2.2 Progress and highlights of scientific results in 2007

2.3 External financing and resources

2.4 Visits abroad

2.5 Papers read at scientific conferences, symposia, meetings etc.

2.6 Visiting academics

2.7 Acting as Opponent and pre- examinations of doctoral disser- tations

2.8 Membership in scientific and schol- arly societies

2.9 Refereeing and Other Publishing Activities

3 High Energy Astrophysics

3.1 General approach

3.2 Science topics

3.3 The ESO-Sampo project

3.4 External financing and resources

3.5 Tests of learning

3.6 Visits abroad

3.7 Papers read at scientific conferences, symposia, meetings etc.

3.8 Membership in scientific and schol- arly societies

3.9 Acting as Opponent and pre- examinations of doctoral disser- tations

3.10 Refereeing and Other Publishing Activities

4 Planetary System Research

4.1 Research activities