Ruprecht-Karls-Universität Heidelberg
SFB Seminar

SFB Seminar

→ Cluster Meeting       → Seminar on scientific results from the Gaia mission

Seminar on SFB-related science

The SFB seminar is dedicated to the presentation and discussion of SFB research results as well as of ongoing projects and their objectives. All students and scientists, including those who are not SFB members, are very welcome to attend. The seminar takes place on Wednesdays from 15:15 to 16:45 at the ARI basement seminar room and is broadcast to MPIA Seminarraum 306, LSW Seminarraum Nordinstitut, and HITS Konrad Zuse meeting room. SFB seminar talks are announced through HePhySTO, the Heidelberg Physics Seminar Talks Organizer.

  • Martina Donnari (MPIA Heidelberg):
    Overview of the simulated Milky Way galaxies in TNG50 and TNG100 and comparison to Auriga and NIHAO

    I will give an overview of the simulated data our SFB projects will be based upon. I will present the main characteristics of earlier numerical zoom-in simulations of Milky Way-like galaxies in concert with their main findings which agree with some observational constraints of our Galaxy. Particularly, I will focus on the Auriga and NIHAO projects, which have provided a landscape of the numerical modelling of Milky Way-like objects. Then, I will give an overview of the TNG50 simulation, the smallest physical volume simulation of the IllustrisTNG project, that will bridge the gap between zoom simulations of individual galaxies and large cosmological volumes. I will illustrate the practical starting point of the project and how the TNG50 outcomes will be used. I will hence focus on structural properties of the simulated Milky Way-like TNG50 and TNG100 galaxies, providing a preliminary comparison to Auriga and NIHAO's outcomes.
  • Nadine Neumayer (MPIA Heidelberg)
    Building up the Center of the Milky Way

    The supermassive black hole at the center of the Milky Way is surrounded by a massive cluster of stars, the nuclear star cluster. Hosting about 10^7 stars within the central 10pc of the Galaxy, the Milky Way nuclear star cluster is one of the densest stellar systems in the universe, and the closest of its kind. In fact, nuclear star clusters are observed in the majority of galaxies in the nearby universe, and still, it is not entirely clear how these dense stellar objects form. At a mere distance of about 8kpc, the Milky Way nuclear cluster can be spatially resolved into individual stars and allows us to determine their kinematic and stellar population information with tailored observing programmes. This makes the Galactic Center the perfect local reference object for understanding the structure and assembly history of nuclear star clusters in general. In this talk I will review our current knowledge of the Milky Way nucleus and will briefly outline the SFB subproject B8 “Building up the Center of the Milky Way”.
  • Prasanta Kumar Nayak (Indian Institute of Astrophysics):
    UVIT- HST- Gaia-VISTA study of star cluster Kron 3 in the Small Magellanic Cloud: A cluster with a large spread in metallicity

    A good number of massive intermediate age (around a few Gyr) metal-poor star clusters in the Magellanic Clouds (MCs) show extended main-sequence turn-off, that can not be explained by photometric errors or stellar binarity. Kron 3 is one such cluster, located to the west of the main body of the Small Magellanic Cloud which has a range of estimated radius as well as age. In this study, we have demonstrated the power of UVIT- HST- Gaia-VISTA combination to study star clusters in the MCs. We take advantage of the resolution of the HST in the central region of the cluster and the coverage of Gaia and VISTA for outer region, to combine with the UVIT data, where we have used photometry in the NUV band with a large spatial coverage. We have estimated the radius of the cluster Kron 3 as 2.0 arcmin from the UVIT and Gaia data. For the first time, we report the identification of NUV bright red clump (RC) stars and the extension of RC stars over two magnitudes both in colour and magnitude axis in NUV vs (NUV - optical) CMD. We find that the extension of RC is an intrinsic property of the cluster and not due to field star contamination. With the help of theoretical isochrones, we suggest that Kron 3 exhibits multiple stellar populations with a possible age range of 6-8 Gyr and a metallicity range of [Fe/H] = -2.0 to -1.0. Theoretical spectral fits to spectral energy distribution of RC stars confirm the metallicity spread among the RC stars. The temperature of RC stars falls in a very small range of 5000-5500 K, indicating that these are indeed RC stars. We suggest that a spectroscopic study of RC stars can throw more light on the metallicity spread present in the cluster.
  • Andreas Koch (ARI/ZAH):
    Hunting abundance spreads in globular clusters of the LMC

    It is now well established that Globular Clusters (GCs) in the Milky Way exhibit complex, multiple stellar populations that go alongside with variations in the abundances of certain chemical elements. Here I will present our results from a Stromgren-photometry study in old GCs in the LMC that indicate that all but one object exhibit no evidence for any significant metallicity spread.
SFB Members' Assembly  (ARI seminar room first floor)
We ask all SFB members (SFB PIs and SFB-employed postdocs as of January 2019) to attend. This is important also in order to ensure that the Members' Assembly can vote. Details will be provided at this internal webpage.

  • Andreas Bauswein (GSI Helmholtzzentrum für Schwerionenforschung Darmstadt)
    Compact object mergers and r-process nucleosynthesis
    (odp file with movie)
    This talk gives a brief overview on compact object mergers. The electromagnetic counterpart of the first unambiguously observed neutron star merger provides very strong evidence that compact object mergers play a major role for the Galactic enrichment by heavy elements formed through the rapid neutron-cpature process. I will describe the different channels of mass ejection and nucleosynthesis in compact object mergers and sketch the goals of the corresponding SFB project.
  • Andreas Quirrenbach (LSW/ZAH):
    4MOST - Science and Instrument

    In 2021, ESO's 4m Vista Telescope will be converted into a spectroscopic survey facility, called 4MOST. With 2436 fibers, 4MOST will be able to obtain 812 high-resolution spectra (R=20,000) and 1624 low-resolution spectra (R=6,000) simultaneously in a field-of-view with 2.5 degrees diameter. In 2018, the project passed its critical design review; it has now entered the construction phase. The LSW is contributing two major sub-systems to 4MOST: the high-resolution spectrograph and the control software. The 4MOST Consortium is preparing a set of large surveys. One of them will obtain 1.5 million high-resolution spectra of Milky Way halo stars (PI: N. Christlieb, LSW). The ESO community will be invited in 2019 to propose additional projects for 4MOST. I will summarize the status of 4MOST, and provide an overview of the further path towards first light and scientific exploitation of the instrument.
  • Andrew Winter (University of Cambridge)
    Quantifying the relationship between stellar birth environment and protoplanetary disc dispersal

    The mass and time available for planet formation is strongly dependent on the stellar birth environment. Both external photoevaporation induced by far ultraviolet photons and star-disc encounters are capable of accelerating protoplanetary disc (PPD) dispersal. I quantify the influence of the two mechanisms in observed young stellar environments and find that external photoevaporation generally dominates over encounters. I further find that the influence of photoevaporation causes PPDs to disperse quickly (within ~3 Myr) for the majority of stars in many local stellar clusters and associations. PPDs around low mass stars are more quickly dispersed due to a shallower gravitational potential and this effect should be detectable in samples of observed discs. Finally, I discuss how the primordial gas properties on galactic scales can be used to infer timescales for disc dispersal outside of the Solar neighbourhood, and the consequences for expected exoplanet frequency.
  • Renate Hubele (HdA & ARI/ZAH)
    A tourist guide to the discworld - Public outreach in the SFB

    The goal of SFB outreach activities is to communicate the fascination and relevance of Galactic astronomy to the general public and, in particular, to address younger audiences. Several activities and outreach materials explaining about Galactic science targeted at high school students and teachers have been developed and we plan to continue the development and dissemination of these materials nationwide. In order to increase the general visibility of SFB research, we make use of exhibition elements, visualisations, online videos, printed materials, public talks, classical and social media. In my talk I will give an overview about current and future outreach activities of the SFB and will discuss any further ideas presented by SFB scientists.
  • Camilla Hansen (MPIA Heidelberg)
    Metal-poor stars unveil a new view of the Sagittarius Dwarf Galaxy

    Sagittarius (Sgr) is a massive dwarf galaxy in the Milky Way (MW) halo and it has undergone several stripping events. Previous studies were restricted mainly to a few, metal-rich ([Fe/H]~-1) stars that suggested a top-light IMF. Here I present the first high-resolution, very metal-poor stellar sample in the main body of Sgr spanning metallicities from [Fe/H]= -1 to -3. We have derived abundances of 13 elements namely C, Ca, Co, Fe, Sr, Ba, La, Ce, Nd, Eu, Dy, Pb, and Th, where abundances of Sr, Pb, and Th are presented here for the first time. These elements allowed for a determination of stellar ages using nuclear cosmochronology and further provided a challenge to the interpretation based on previous metal-rich studies. The high level of Ca indicates that more massive supernovae (SNe) must have existed and polluted the early ISM of Sgr before it lost its gas. This is in contrast with a top-light IMF with no massive star pollution. Overall, our abundances from Sgr mimic those of the metal-poor halo rather than those representing the metal-rich disc. Our most metal-poor star ([Fe/H]~-3) indicates a pure r-process pollution. Based on star-to-star scatter and abundance patterns, a mixture of low and high mass AGB stars and massive SNe (15-25Mo) are necessary to explain these. Hence, stars stripped from Sgr and similar dwarf galaxies could indeed be building blocks of the MW halo and possibly offer an explanation for metal-poor, s-rich stars in the Galactic halo.
  • Michael Hanke (ARI/ZAH)
    ATHOS - a cross-survey tool for determining stellar parameters

    Existing and future large-scale spectroscopic surveys feed a demand for fast and efficient tools for the determination of fundamental stellar parameters. Such tools should not only comprise customized solutions for one particular survey or instrument, but, in order to enable cross-survey comparability, be capable of dealing with spectra from a variety of spectrographs, resolutions, and wavelength coverages. To meet these ambitious specifications, we developed ATHOS (A Tool for HOmogenizing Stellar parameters), an analysis tool that adopts easy-to-use, computationally inexpensive analytical relations tying flux ratios of designated wavelength regions in optical spectra to the stellar parameters effective temperature, iron abundance, and surface gravity. I will outline our fundamentally new approach and its empirical derivation from a stellar benchmark sample. ATHOS' extraordinary performance in terms of accuracy, precision, and speed will be demonstrated on a selection of spectroscopic surveys, such as the Gaia-ESO survey. Finally, I will use the horizontal branch star HD~20 as a showcase to prove that our new parametrization method can compete even with the more resource-demanding analysis techniques tailored to the in-depth study of much smaller stellar samples.
  • Somayeh Sheiknezami (Institute for Research in Fundamental Sciences, Tehran)
    Exchange of mass and angular momentum in accretion disk forming jet systems

    Jets and outflows from YSO and AGNs affect their environment, and, thus, the formation process of the objects that are launching them. Numerous studies investigate effects of such feedback mechanisms in star and planet formation and galaxy formation. However, a quantitative investigation of how much mass, momentum, or energy from the infall is actually recycled into a high-speed outflow needs to resolve the innermost jet-launching region and to model the physical process of launching directly. According to the current understanding, accretion and ejection are related to each other. One efficient way to remove angular momentum from a disk is to connect it to a magnetized outflow. In this talk, I will present the recent studies of the detailed physics of accretion-ejection structure in the inner part of the disk focusing on launching process of an outflow from a magnetically diffusive accretion disk The main question we address is which kind of disks launch jets and which kind of disks do not? in addition, I will talk about the observed non-axisymmetric structures in the disk-jet structure by extending the model to 3 dimensions and including the companion in the setup.
  • José G. Fernández-Trincado (Universidad de Concepción)
    The APOGEE/VVV view of chemically unexplained giant stars abnormally rich in light and heavy elements

    APOGEE contains more than hundred thousand new giant stars. This enabled us to collect an unprecedented and homogeneous sample of giant stars with light-element abundance variations similar to observed in "second-generation" globular cluster stars. If they are really former members of dissolved globular clusters, stars in these groups should show some of the basic SG-like chemical patterns known for stars currently belonging to the Milky Way globular clusters, such as depletion in C and O together with N and Al enrichments. We will present the results of an updated census of SG-like stars from a near-infrared manual analysis using the Brussels Automatic Stellar Parameter (BACCHUS) code to provide the abundances of C, N, O, Mg, Si, Al, Fe, Ce and Nd for every line of possible cluster member stars, which they migrate to the disk, halo and bulge as unbound stars, and become part of the general stellar population of the Milky Way. By combining wide-field time-series photometry with APOGEE-2S spectroscopy data, we are in a good position to put the big picture together. The VVV survey have produced a large variability dataset towards the Milky Way bulge and disk, including data in the near-IR (J and Ks). These data will allow us to place constraints on the "polluters" that are responsible for the chemical peculiarities, with candidates including TP-AGB stars, binary mass transfer, accretion of material from the winds of AGB stars, etc. A cross match between VVV sources and APOGEE targets is ongoing.
17.10.2018 – no seminar

07.02.2018 SFB Members' Assembly  (ARI seminar room first floor)

   Special announcement
   24.09.-26.11.2017 – Series of public lectures on SFB topics
   Astronomie am Sonntagvormittag – Die Milchstraße: Faszination Heimatgalaxie
   11:00, Haus der Astronomie

   Special announcement
   28.07.2017 – Königstuhl Colloquium
   Hans-Walter Rix (MPIA): SDSS-V: Pioneering Panoptic Spectroscopy
   15:00, MPIA lecture hall

19.07.2017 – No seminar

  • Kareem El-Badry (UC Berkeley): Self-consistently modeling the spectra of unresolved binary stars
    PDF Keynote

    Approximately half of solar-type stars reside in binary systems. Beyond the solar neighborhood (< 20 pc), most binary systems cannot be spatially resolved, and only a small fraction of binary systems have short enough periods to be identified via a Doppler shift. Nevertheless, binarity change stellar spectra: the observed spectrum of an unresolved binary system is a superposition of two single-star spectra with different effective temperatures. I will show that ignoring binarity when fitting the spectra of unresolved binaries leads to significant systematic errors in the derived stellar parameters. I will then introduce a flexible spectral fitting model which includes the possibility of binarity and corrects these errors. I will discuss the prospects for measuring the Galactic binary population by fitting spectra from large, low-resolution spectral surveys.
  • Camilo Penaloza (Cardiff University): CO line ratios in Molecular Clouds: Tracing physical properties and the impact of environment
    The use of CO line intensity ratios in Giant Molecular Clouds (GMCs) can help determine the excitation conditions of the molecular gas. Specifically different environments produce variations in the line intensity ratio. We focus on mimicking the CO emission for simulated GMCs. We perform a set of smooth particle hydrodynamics (SPH) simulations with time-dependent chemistry, in which environmental conditions such as mass, density, size, metallicity and the Interstellar Radiation Field were systematically varied. The simulations were then post-processed using radiative transfer (via RADMC-3D) to produce synthetic emission maps. These are created for different lines of CO’s rotational ladder as well as different CO isotopes. I will show how line ratios can be used to trace physical properties as well as the impact of environment on these.

21.06.2017 07.06.2017
  • Radek Smolec (Nicolaus Copernicus Astronomical Center): New Perspective on Classical Pulsators
    I will present the recent discoveries of new forms of pulsation in classical pulsators. These include multi-periodic and modulated pulsation. Double-periodic pulsation must be common phenomenon among first overtone pulsators, both Cepheids and RR Lyrae stars. The commonly observed additional variability is of low amplitude and cannot be interpreted as due to radial pulsation. First model which provides the selection mechanism and identification for non-radial modes was proposed and offers the possibility of studying the interiors of classical pulsators. Low-amplitude instabilities in classical pulsators are also more common than previously thought. The recent example I will focus on is quasi-periodic modulation in fundamental mode classical Cepheids.
  • (Thales Gutcke's talk had to be cancelled)

29.05.2017, 11:30 – special guest seminar Note changed room: ARI main seminar room, 1st floor

  • Masato Kobayashi (Nagoya University, Japan): Evolutionary Description of Giant Molecular Cloud Mass Functions in Galactic Disks
    (Host: D. Kruijssen)
    Recent radio observations show that giant molecular cloud (GMC) mass functions noticeably vary across galactic disks (e.g., Colombo et al. 2014). High-resolution magnetohydrodynamics simulations show that multiple episodes of compression are required for creating a molecular cloud in the magnetized interstellar medium (e.g., Inoue et al. 2012). To understand time evolution of GMC mass functions, we formulate the evolution equation for the GMC mass function to reproduce the observed profiles, for which multiple compressions are driven by a network of expanding shells due to H II regions and supernova remnants. We also introduce the cloud-cloud collision (CCC) terms in the evolution equation in contrast to previous work. In this seminar, I would like to present computed time evolutions and the following two suggestions: (1) the GMC mass function slope is governed by the ratio of GMC formation timescale to its dispersal timescale whereas the CCC effect is limited only in the massive end of the profile, (2) almost all of the dispersed gas contributes to the mass growth of pre-existing GMCs in arm regions whereas less than 60 percent contributes in inter-arm regions. Our results suggest that measurement of the GMC mass function slope provides a powerful method to constrain those GMC timescales and the gas resurrecting factor in various environments across galactic disks.

24.05.2017 Special seminar and get-together at ITA: Modeling the interstellar medium in different environments
      Hosted by Ralf Klessen and Simon Glover
      Philosophenweg 19 (ITP), seminar room
(note: no video broadcast)   → Directions

  • Daniel Rahner: Winds and radiation in unison – feedback from young massive clusters
  • Robin Treß: Simulations of the Galactic Center: a possible explanation for the CMZ asymmetry
  • Mattia Sormani: Periodicity makes galactic shocks unstable
Public transport:
  • From MPIA, LSW & HdA: Bus 39 at 14:23 from stop Sternwarte, arrives Bismarckplatz 14:58
  • From HITS: Ruftaxi RNV 1005 (request in advance)at 14:42 from HITS, arrives Schlierbach-Ziegelhausen S-Bahnhof 14:54, from there bus 735 at 15:00, arrives Bismarckplatz 15:13 – let T. Lisker know if you plan to take this connection

10.05.2017 – No seminar

  • Oleksiy Golubov (Kharkiv University): The local rotation curve of the Milky Way
    We use a sample of SEGUE G-dwarfs to constrain the local behaviour of the rotation curve of the Milky Way. We find the mean galactocentric rotation velocity of the stars, correct for the asymmetric drift and the vertical gradient of the circular velocity, and construct the rotation curve at the galactocentric radii 7 to 10 kpc. The rotation curve appears flat, with no significant dips in the considered range. Then we use TGAS sample with Gaia parallaxes to constrain the local slope of the rotation curve.
  • Sarah Jeffreson (ARI): Dynamical models of flattened and rotating globular clusters
    We present a family of self-consistent axisymmetric rotating globular cluster models which are fitted to spectroscopic data for NGC 362, NGC 1851, NGC 2808, NGC 4372, NGC 5927 and NGC 6752 to provide constraints on their physical and kinematic properties, including their rotation signals. They are constructed by flattening Modified Plummer profiles, which have the same asymptotic behaviour as classical Plummer models, but can provide better fits to young clusters due to a slower turnover. The models are in dynamical equilibrium as they depend solely on the action variables. We employ a fully Bayesian scheme to investigate the uncertainty in our model parameters (including mass-to-light ratios and inclination angles) and evaluate the Bayesian evidence ratio for rotating to non-rotating models. We find convincing levels of rotation only in NGC 2808. In the other clusters, there is only a hint of rotation (in particular, NGC 4372 and NGC 5927), as the data quality does not allow us to draw strong conclusions. Where rotation is present, we find that it is confined to the central regions. As part of this work, we have developed a novel q-Gaussian basis expansion of the line-of-sight velocity distributions, from which general models can be constructed via interpolation on the basis coefficients.

08.02.2017 SFB Members' Assembly  (ARI seminar room first floor)
We ask all SFB members (current SFB PIs, current SFB-employed postdocs, and elected members) to attend. This is important also in order to ensure that the Members' Assembly can vote. Details are provided at this internal webpage.

  • István Dékány (ARI): The properties of the Galactic bulge as told by its RR Lyrae stars
    The Galactic bulge holds key information on the early formation history of the Milky Way, but efforts aiming to map its detailed present-day structure have not reached a full consensus. Our goal is to accurately map both the space-varying extinction curve in the bulge's foreground, and the 3-dimensional distribution of its oldest stellar population using RR Lyrae stars as tracers. We find non-standard mean optical-infrared extinction ratios and trace large and coherent variations in the reddening curve, in qualitative agreement with independent findings. We employ an unbiased extinction correction to derive an accurate map of the old Galactic bulge. It is remarkably different from the barred structure traced by red clump stars, and shows subtle features requiring further investigation.
  • Eva K. Grebel (ARI): Mapping Multiple Stellar Populations of Globular Cluster Origin in the Field
    Essentially all globular clusters contain multiple stellar populations, and their presence has even been proposed to be a defining characteristic of globular clusters. In contrast, the less massive and usually short-lived open clusters do not show evidence for multiple stellar populations. The origin of photometrically or spectroscopically identified multiple populations remains a major unsolved puzzle though.
    If multiple populations do indeed form exclusively in globulars as our current knowledge suggests, they may be used to trace the globular cluster contribution to the field. Chemically, multiple stellar populations stand out by their light element abundance variations. The search for these chemical signatures among field stars permits us to identify candidates that were likely stripped from globular clusters. An alternative method is the search for stars that are chemically and kinematically consistent with an origin from specific globular clusters (while not necessarily showing light element abundance variations).
    Mapping such present-day field stars will ultimately allow us to quantify the role of globular clusters in the build-up of field populations.

11.01.2017 Special seminar and get-together at HITS, Konrad Zuse meeting room, 2nd floor   (video broadcast on demand)

  • Volker Springel: Simulations of the Milky Way's Formation in a Cosmological Context
  • Christine Simpson: Galactic Outflows and Cosmic Rays
  • Martin Sparre: Cosmological Simulations of Galaxy Mergers
→ Directions to HITS
Transport from MPIA will be arranged (contact T. Henning). From downtown, please let T. Lisker know if carpooling is desired. There is also a convenient public transport connection:
  • From MPIA, LSW & HdA: Bus 30 at 14:48 from MPIA, arrives HITS 15:13.
  • From ARI & ITA: Bus 31 at 14:41 from Mönchhofschule (ARI) and 14:43 from Brückenstraße (ITA), arrives Universitätsplatz 14:54; walk few minutes to bus stop Peterskirche in eastern direction; Bus 30 at 15:01 from Peterskirche, arrives HITS 15:13.
  • Return to MPIA, LSW & HdA: Bus 30 at 17:14 from HITS, arrives MPIA 17:42.
  • Return to ARI & ITA: Bus 30 at 17:14 from HITS, arrives Universitätsplatz 17:25; Bus 31 at 17:32 from Universitätsplatz, arrives Brückenstraße (ITA) 17:42 and Mönchhofschule (ARI) 17:44.

07.12.2016 – No seminar

  • Xiaoting Fu (SISSA): The new PARSEC evolutionary tracks and isochrones with alpha enhancement: Calibration with 47Tuc and improvement on the RGB bump prediction
    Precise studies on the Galactic bulge and multiple populations of globular cluster require stellar model with alpha enhancement and various helium contents. It is also important for extra- Galactic study to have alpha enhanced population synthesis. For this purpose we expand PARSEC model from solar-scaled composition to alpha enhanced mixtures. The new model is calibrated with globular cluster 47Tuc (NGC104). We then apply the calibration and alpha enhanced mixture based on the two 47Tuc populations ( [alpha/Fe] ∼0.4 and 0.2) to other metallicities. The new model closes the gap between the observation and model prediction on the RGB bump. Besides the alpha enhanced metal mixture in 47Tuc, we also calculate evolutionary tracks based on metal mixtures from ATLAS9 APOGEE atmosphere model.
  • Diederik Kruijssen (ARI): The Multi-Scale Physics of Star Formation and Feedback in the Building Blocks of the Milky Way
    Dr. Kruijssen will introduce his new SFB subproject P1.
  • Friedrich Röpke (HITS/ITA): Thermonuclear supernovae as sources of iron group elements in the Milky Way
    Prof. Röpke will introduce his new SFB subproject A10.
  • Claudia Conrad (Mannheim): Open Cluster Groups and Complexes
    It is generally agreed upon that stars form in open clusters and stellar associations, but little is known about structures in the Galactic open cluster population. Are open clusters and stellar associations born isolated or do they prefer to form in groups? Answering this question provides new insight into star and cluster formation, along with a better understanding of Galactic structures.
    In the past decade studies of open cluster groupings were either based solely on spatial criteria or also included tangential velocities for the identification. In contrast to previous approaches, we assumed that real open cluster groupings occupy a well defined area in the sky and show similar velocity vectors. Therefore, we used 6D phase-space information for the detection of open cluster groupings. In addition, we checked the age spread for the potential candidates, to distinguish between genuine groupings and chance alignments.
    We explored the Catalogue of Open Cluster Data (COCD; Kharchenko et al. 2005a,b) and determined 6D phase-space information for 432 out of the 650 listed open clusters and compact associations. The group identification was performed using an adapted version of the Friends-of-Friends algorithm, as used in cosmology, with linking lengths of 100 pc and 10-20 km/s. For the verification of the identified structures, we applied Monte-Carlo simulations with randomised samples. For the linking lengths 100 pc and 10 km/s we detected 19 groupings, including 14 pairs, fours groups with 3-5 members, and one complex with 15 members. The Monte-Carlo simulations revealed that in particular the complex is most likely genuine, whereas the pairs are more likely chance alignments. A closer look at the age spread of the complex and the comparison between the spatial distributions of the young and old cluster population suggested that OC groupings likely originated from a common molecular cloud.
  • Bertrand Lemasle (ARI): Preparing for Public Surveys for the MOSAIC multi-object spectrograph on the E-ELT
    MOSAIC is the future multi-object spectrograph (MOS) for the E-ELT. After giving a brief overview of the instrument and its operating mode, I will highlight some SFB-relevant aspects of the current phase A study (March 2016 – March 2018), during which the conceptual design of the instrument will be refined. The phase A study includes the preparation of public surveys that could follow the implementation of the instrument at the telescope (~2025-26). Even if MOSAIC is a long-term project, it is now that we have to prepare the design of the MOS and accompanying surveys on the largest telescope of the next decades.
  • Elena D'Onghia (University of Wisconsin-Madison): Tidally Induced Offset Disks in Magellanic Spiral Galaxies
    Magellanic spiral galaxies are a class of one-armed systems that often exhibit an offset stellar bar and are rarely found around massive spiral galaxies. Using a set of N-body and hydrodynamic simulations, we consider a dwarf-dwarf galaxy interaction as the driving mechanism for the formation of this peculiar class of systems. We investigate and I will present here the relation between the dynamical, stellar, and gaseous disk center and the bar during and after the interaction. We explain the nature of the offset bar found in many Magellanic-type galaxies, including the Large Magellanic Cloud (LMC) and NGC 3906. In particular, these results, once applied to the LMC, suggest that the dynamical center should reside in the bar center instead of the HI center as previously assumed, pointing to a variation in the current estimate of the north component of the LMC proper motion.

28.09.2016, 15:15 – special guest seminar Note changed room: ARI main seminar room, 1st floor

  • Yutaka Hirai (University of Tokyo): Enrichment of r-process elements in the Local Group galaxies in chemo-dynamical evolution model
    (Host: D. Kruijssen)
    The abundance of r-process elements of stars in the Milky Way (MW) provides clues to clarify the early evolutionary history of galaxies. Astronomical high dispersion observations show that metal-poor stars in the MW halo have large star-to-star scatters in the distribution of r-process elements. Neutron star mergers (NSMs) are one of the most promising sites of r-process. Previous chemical evolution studies, however, suggested that the merger timescale of NSMs is too long to reproduce the observed scatters. In this study, we performed a series of N-body/hydrodynamic simulations of the MW progenitor galaxies. We show that the scatters can be explained by NSMs due to the slow chemical enrichment of such galaxies. This result suggests that stars in the MW halo formed with a star formation rate of less than 10^-3 Msun/yr. We also find that the dynamical time of halos affects the early evolutionary history of galaxies. Our results demonstrate that the future observations of r-process elements in metal-poor stars will be able to constrain the early chemo-dynamical evolution of the Local Group galaxies.


  • Dr. David Martinez-Delgado (ARI): Searching for substructures around the Milky Way dwarf satellites with a telephoto lens
    I will present the proof of concept and first results on the search for stellar substructures around a sample of Milky Way dwarf satellites, as part of the objectives of the SFB881 subproject A2. In particular, I will show deep optical images of the Magellanic Clouds using a low cost telephoto lens to explore stellar substructures in their outskirts, and a comparison of these results with detailed simulations of the LMC-SMC interaction. Finally, I will briefly discuss the future plans for installing the instrumental equipment of the SFB881 A2 project devoted to undertake a search for distant, diffuse Milky Way satellites in a huge sky area.
  • SFB Members' Assembly

27.01.2016 – No seminar

  • Clio Bertelli Motta (ARI): Chemical composition of Milky Way open clusters in APOGEE and SEGUE
    Open clusters are very interesting objects not only because they are known to be the birthplace of stars, but also because studying their chemical composition can teach us a lot about stellar and galaxy evolution. We crossmatched the Kharchenko et al. (2013) catalogue of open clusters with the APOGEE and SEGUE spectroscopical surveys. After an accurate membership analysis of the stars found within the radius of each cluster, based on proper motions, radial velocity, colour-magnitude diagrams and metallicities, we investigated the chemical abundances of several elements of the selected member stars resulting from the APOGEE pipeline ASPCAP. In few cases, for clusters very well sampled with giants, it was possible to observe the effects of the first dredge-up after the sub-giant branch on the atmosphere of the stars. Besides, for some of the clusters we could compare the results of ASPCAP with those of the SEGUE pipeline SSPP and, in the case of SEGUE spectra, we were also able to determine the metallicities and the alpha abundances as well as the radial velocities with the code SP_Ace (Boeche & Grebel 2015). In this talk I will give an overview on the method and the results that we obtained so far.
  • Dr. Joachim Bestenlehner (MPIA): Massive stars and the chemical enrichment of the universe
    The first part of my talk will be about massive stars as progenitors of type II, Ib/c and pair-instability supernovae. Until the first SN Ia occurred these supernova types were the main sources to chemically enrich the early universe. The second part will be about my on going and future research within Gaia-ESO.

09.12.2015 – No seminar

  • Dr. Julio Chaname (Pontificia Universidad Catolica de Chile): Globular clusters and the assembly of the stellar halo
    In the context of the hierarchical framework of cosmological structure formation, the stellar halos of galaxies like the Milky Way assembled via the accumulation and shredding of smaller entities formed at earlier times. Until recently, the focus of the search and characterization of such building blocks has been on dwarf galaxies, but evidence has been accumulating that hint at a significant contribution from massive globular clusters (GCs) as well. I will briefly review current constraints on such contribution, which come from a variety of indicators, and will present results from our work on the chemodynamical tagging of moving groups in the solar neighborhood that have been historically associated to existing GCs such as omega Centauri and others.
  • Prof. Eva K. Grebel (ARI): Recent Results from Abundance and Radial Velocity Surveys of Milky Way Field Stars
    The stellar radial velocities and abundances measured by recent and ongoing massive spectroscopic surveys are providing an unprecedentedly detailed picture of the evolution of our Galaxy. In combination with photometric and astrometric information, they reveal the enrichment histories of the Milky Way's field populations and make the determination of age-metallicity-velocity dispersion relations for the different Galactic components possible. The rapidly growing data bases help us to uncover abundance gradients and mixing, to reveal dynamical resonances or parent clusters in which the field stars formed originally, or to trace yet other field stars back to accreted dwarf galaxy progenitors. The emerging picture of Galactic evolution is complex, full of surprises, and still evolving. In the future, new multi-object facilities such as 4MOST, MOONS, and WEAVE will allow us to further refine our understanding of Milky Way evolution. In my talk, I will highlight some of the important breakthroughs obtained in recent years.   [Note: This is a review talk given at the Multi-Object Spectroscopy conference in Cefalu in September 2015.]

11.11.2015 – No seminar

  • Prof. Hans-Walter Rix (MPIA): What processes set the structure of the Galactic disk
    This is adapted from a keynote I gave at a recent ESO workshop on spectrosopic surveys. After a few broad comments on the role of theses surveys, I will talk about recent work with APOGEE that allowed to look at the abundance-dependent radial structure and the age structure of the Galactic disk empirically, spanning 4 to 15 kpc, with surprising and exciting results.
  • Dr. Edward Schlafly (MPIA): The Optical-Infrared Extinction Curve and its Variation in the Milky Way
    The dust extinction curve is an important diagnostic of the physics of the interstellar medium, as well as a critical element to many observational programs. Detailed studies of the extinction curve and its variation have so far been limited to samples of hundreds of specially chosen stars. We make new measurements of the dust extinction curve and its variation towards of tens of thousands of stars using the APOGEE spectroscopic survey in combination with photometry in ten bands, from Pan-STARRS1, 2MASS, and WISE. We find that the extinction curve in the optical through infrared is well characterized by a one-parameter family of curves described by R(V), with little need for further parameters. The local curvature of the extinction curve increases with decreasing R(V) throughout the optical and infrared: the extinction curve in the infrared, while less variable than in the optical, is not "universal", in contrast to several widely-used extinction curve parameterizations. Meanwhile we find that the optical extinction curve is somewhat more uniform than suggested in past works, with σ(R(V)) = 0.2, and with less than two percent of sight lines having R(V) > 4. However, significant spatially coherent variations in R(V) do exist. The primary variations are on scales much larger than individual molecular clouds, indicating that grain growth in dense molecular cloud environments is not the primary driver of R(V) variations in dust at large. Indeed, we find no correlation between R(V) and dust column density up to E(B−V) ≈ 2.
  • Prof. Ralf Klessen (ITA): Modeling Galactic-Scale ISM-Dynamics and Star Formation
  • Reza Moetazedian (ARI): Vertical heating of the Galactic disc: Contribution of infalling satellites
    There exist few mechanisms which are believed to be responsible for the heating of the Milky Way disc, i.e. increasing the velocity dispersion of disc stars. Within the framework of this analysis, using high resolution N-body simulations, we would like to quantify the contribution of infalling satellite galaxies to the vertical heating of the galactic disc. In order to have a realistic picture, the properties of satellites are extracted from cosmological simulations of Milky Way like systems. We also take advantage of initial conditions for the case of isolated Milky Way which is in much better equilibrium state than previous studies.

Seminar dates in previous terms:


Talks will be broadcast to LSW and MPIA

  • Dr. Robert Grand (HITS/ARI): Probing the effects of secular evolution in numerical simulations of the Milky Way
    In recent years, radial migration has been highlighted to be an important evolutionary process that has helped shape the current state of the Milky Way. For example, it can explain the scatter in the age-metallicity relation and metal distribution function in the solar neighbourhood, and has been indicated to affect structural parameters as well. To investigate this phenomenon, we perform a series of simulations with the state of the art Arepo hydrodynamics code, and make use of a cosmological zoom technique that allows us to simulate the evolution of a Milky Way sized haloes from z=127 to present day at high resolution. We focus on evolution after z=1, and find that radial migration does not change the radial metallicity gradient in galaxies with spiral structure only, but can flatten it if a bar is present. In all cases the metal distribution function broadens at all radii. We find also that radial migration does not seem responsible for disc thickening, and instead may actually help keep the disc thin. This is however a complicated process with many dependencies, including the formation history of the disc component (inside-out formation) and satellite interactions.
  • Dr. Piercarlo Bonifacio (GEPI, Observatoire de Paris): Carbon enhanced metal-poor stars: new insights from the TOPoS project
    It has been known for the last twenty years, among metal-poor stars the fraction of carbon-enhanced metal poor stars (CEMP, [C/Fe]> +1) increases with decreasing metallicity. I will present new results from the TOPoS project, including three newly discovered CEMP stars with metallicity below -4.5, raising to a total of nine the known metal-poor stars in this metallicity regime. Eight out of nine of these stars are CEMP. Five of these nine stars are unevolved (TO or SGB) and only one has a measured Li abundance, about 0.4 dex below the Spite plateau. A low lithium abundance seems to be a general characteristic of these stars. Another striking characteristic of the extremely metal-poor stars is the very low scatter in the [X/Ca] ratios for all elements heavier than Si, in spite of the fact that they span 3 orders of magnitude in Fe (or Ca) abundance. Our proposed scenario for the formation of the first generations of stars, is the formation of several massive stars in a mini-halo, at least one of which should explode as a faint supernova, to produce the excess carbon. I will finally discuss future perspectives for the search of and analysis of EMP stars.


First talk will be given at ARI and broadcasted to MPIA, second talk will be given at MPIA and broadcasted to ARI

  • Dr. Maria Bergemann (MPIA): High-precision stellar spectroscopy and fundamental parameters of stars
    Spectroscopic observations of stars have shaped our understanding of the Galactic evolution and stellar structure. This is because spectra of stars are the only way to determine their chemical composition, which is the fundamental resource to study cosmic nucleosynthesis in different environments and on different time-scales. Research in this field has never been more exciting and important to astronomy: the ongoing and future large-scale stellar spectroscopic surveys are making gigantic steps along the way towards high-precision stellar, Galactic, and extra-galactic archaeology.
    However, the data we extract from stellar spectra are not strictly-speaking ‘observational’. These data - fundamental parameters and chemical abundances - heavily rely upon physical models, which describe atmospheres of stars and provide model predictions for the analysis of raw observations. I will describe our efforts to provide the most realistic models of radiation transport in stellar atmospheres, based upon 3D non-local thermodynamic equilibrium physics. I will outline the fundamental principles, show how these improvements transform quantitative spectroscopy, and discuss the implications for stellar and Galactic chemical evolution.
  • Dr. Eugene Magnier (IfA, University of Hawaii): The Pan-STARRS1 Astrometric Survey
    The Pan-STARRS1 Science Consortium is preparing for the public release of data from the 5 year PS1 Sky Surveys. The 3pi Survey component includes ~75 billion measurements of ~3 billion stars and galaxies. The large data set allows us to explore a wide range of systematic effects, helping to tie down the astrometric and photometric calibration. I will discuss the upcoming release with an emphasis on astrometry.  


  • Priv.-Doz. Dr. Coryn Bailer-Jones (MPIA): Mapping dust in the Galaxy in three dimensions with Gaia
    We are developing a nonparametric model to reconstruct the three-dimensional (3D) distribution of dust in the Milky Way. Our approach uses observed line-of-sight extinctions towards stars at different positions in the Galaxy. These give the integrated dust density along each line-of-sight. Making weak assumptions about the correlation of the dust, we infer the most probable 3D distribution of dust which explains the observed extinctions, also at points which have not been observed. Given distances and extinctions estimated from the Gaia photometry and astrometry for tens of millions of stars, we plan to build a detailed map of dust in our Galaxy.
  • Dr. Nick Abel (Cincinnati): Physical conditions in Orion's Veil
    Orion's Veil is a foreground cloud of gas and dust, between us and the Trapezium cluster, which is the primary source of extinction towards the Nebula. Observations in the radio and optical regime have allowed us to create maps of the extinction and line-of-sight magnetic field across the Veil. These maps, combined with optical and UV absorption line studies towards the Trapezium stars, provide a wealth of observational data which makes the Veil an ideal laboratory with which to study the physical processes in the ISM. This talk will review the observations of the Veil, and how these unique set of observations combined with theoretical calculations have improved our understanding of the geometry, chemistry, and energetics of the environment. Specifically, this merger of observation and theory has allowed us to determine that the Veil’s energetics is dominated by magnetic fields, have helped us to explain the lack of molecules in the region, and has allowed us to determine the thickness of the Veil and its distance away from the Trapezium.


– No seminar –


  • Dr. Corrado Boeche (ARI): SP_Ace: a new code to estimate stellar parameters and elemental abundances
    Corrado will outline the method that SP_Ace employs to derive stellar parameters and chemical abundances and show its performances on synthetic and real spectra.
  • Dr. Anna Sippel (Swinburne): Globular cluster models star by star
    Using N-body models of globular clusters can provide an excellent addition to observations and allows to analyze the clusters according to each single star's influence. Anna uses this approach to study remnant black hole dynamics or the influence of bright stars on cluster size and colour and shows some of the insights she and her collaborators have gained from 'observing' those models.


Video link available at MPIA (Seminarraum) and LSW (Seminarraum Nordinstitut)

  • Prof. Eva K. Grebel (ARI): A8: The Globular Cluster Contribution to the Build-up of the Galactic Halo
    Globular clusters in the Galactic halo are believed to have formed in part in situ or to come from accreted dwarf galaxies. In both cases, they can contribute stars to the halo field star population, particularly when experiencing dissolution processes due to internal or external effects. There is growing evidence that all massive globular clusters show light element abundance variations (possibly due to a second generation of star formation). A subset of stars lost from globular clusters can be identified in the halo due to their unusual element abundance ratios and allows us to constrain the fraction of halo field stars once born in massive globulars.
  • Prof. Andreas Quirrenbach (LSW): 4MOST - 4-meter Multi-Object Spectroscopic Telescope
    4MOST is a wide-field, high-multiplex spectroscopic survey facility under development for the VISTA telescope of the European Southern Observatory. Its main science drivers are in the fields of galactic archeology, high-energy physics, galaxy evolution and cosmology. Andreas will give a short introduction to the technical concept and scientific goals of 4MOST.


– No seminar –


  • Simon Glover (ITA): "Star formation at the centre of the Milky Way"
    Simon will talk about the scientific goals of the SFB subproject B8, and will review the progress that they've made on tackling these goals during the period when this was funded as a pilot SFB project.




  • Paolo Bianchini (MPIA) " Formation of extended star clusters"
  • Johannes Esser (ARI) "Star formation in the Large Magellanic Cloud"


  • Peter Zeidler (ARI) "A HST multi band survey of the young massive star cluster Westerlund 2"
  • Oleksandr Veles (ARI) "The  abilities  of  the new yebisu-OpenCL library of the phi-GRAPE+GPU code. The current performance analysis & status of the SUPERBOX+FFT/GPU code."








  • No seminar: Evaluation meeting


  • SFB practice talks: multiple speakers






  • Jorge Penarrubia (Guest) "Testing cosmology with Milky Way dwarf spheroidals"
  • Avon Huxor (ARI) "Tracing Milky Way halo features with carbon stars"


  • Corrado Boeche (ARI) "1. chemical gradients in the Milky Way from the  RAVE data 2.SPACE: a new code to estimate stellar parameters and chemical abundances"
  • Andreas Ernst (ARI) "Roche volume filling of star clusters in the Milky Way"


  • Dimitrios Gouliermis (ITA/MPIA) "Assessment of the stellar topology in  a star-forming complex."
  • John Vickers (ARI) "Runaway red dwarfs"


  • Martin Altmann (ARI) "Gaia science - how to include the Gaia team in  science projects both inside and outside the SFB"
  • Camille Hansen (LSW) "Stellar abundances as tracers of heavy element  formation"'


  • Federico Marinacci (HITS) "Moving-mesh cosmological simulations of disc galaxy formation"


  • Pauline Assmnan (Universidad de Chile) "Star Clusters as building  blocks of dSph galaxies"
  • Frederik Schoenebeck (ARI)  "Slit spectroscopy with X-shooter: A never ending story of tweaks and calibrations"


  • Markus Demleitner (ARI) "Data Publishing: The Why, What, and How"
  • France Allard (CRA Lyon) "Issues when modeling the atmospheres of 
    VLMs, brown dwarfs, and gas giant planets"


  • Stefan Schmeja (ARI) "New open clusters at high Galactic latitudes"
  • Rainer Spurzem (ARI) "Mass segregation in rotating star clusters"
      (Fokker-Planck and massive GPU accelerated NBODY6++ simulations)"


  • Laura Watkins (MPIA) "Discrete dynamical modelling of Omega Centauri"
  • Nikolay Kacharov (LSW) "Multiple populations in globular clusters"


  • Volker Gaibler (ITA) "Jet feedback in the Milky Way"
  • Sonia Duffau (LSW) "The GAIA ESO survey: towards the first data release"


SFB Assembly

  • First Funding Period from Jan 2011 – Dec 2014
  • Planning for the 2nd  Funding Perio


  • Edward Schlafly (MPIA): "Mapping the Milky Way in 3D with PS1"
  • Mohamad Abbas (ARI): "A Search for RR Lyrae Stars in Sky Surveys"


  • Betrand Goldman (MPIA): "The very-low mass content of the Hyades"
  • Alberto Nardin (ARI): "The third integral of motion and the velocity ellipsoid in the solar neighbourhood"


  • Rahul Shetty (ITA): "Evidence for a non-universal, sub-linear Kennicutt-Schmidt relationship using hierarchical Bayesian linear regression"
  • Alex Buedenbender (MPIA): "Kinematical 3D analysis of G Dwarfs and the velocity ellipsoid"


  • John Vickers (ARI): "Blue Horizontal Branch Stars in Pan-Starrs 1"
  • Christoph Olczak (ARI): "Weighing the (rotating) Arches cluster: the first consistent mass estimate" 


  • Thomas Gerner (MPIA): "Toward a chemical evolutionary sequence in high-massstar formation"
  • Laslo Szucs (ITA): "Chemical post-processing of GMC simulations"


  • Daniela Carollo: "The Structure and Chemistry of the Halo System of the Milky Way" (Special guest talk)


  • Christoph Olczak (ARI): "The dynamically driven evolution of proto-planetary discs in young star clusters"
  • Matthias Frank (ARI): "The dynamical state of the outer halo globular clusters Palomar 4 and 14"


  • Stefan Schmeja (ARI): "A Search for Old Open Clusters in the Solar Neighbourhood"
  • Jan Rybizki (ARI): "A semi-analytic chemodynamical evolution model of the Milky Way disc"


  • Rowan Smith (ITA): "A universal signature of collapse in massive star forming regions"
  • Christian Fendt (MPIA): "Jet launching simulations of diffusive MHD disks"


  • Andreas Just (ARI): "Extending local disc models based on RAVE and SEGUE data"
  • Avon Huxor (ARI): "Tracing the Sagittarius streams with long-period variables"


  • Pier-Emmanuel Tremblay (LSW): "Our night sky: outside of the Hyades tidal radius"
  • Faviola Molina (ITA): "Can we trust CO emission as a probe of the densities and temperatures of molecular clouds?"


  • Rahul Shetty (ITA): "Dust SEDs in the era of Herschel and Planck: a Hierarchical Bayesian fitting technique"
  • Corrado Boeche (ARI): "Abundance-kinematic relationship of the Galactic disk with RAVE"


  • Simon Glover (ITA): "Is molecular gas necessary for star formation?"
  • Eva Grebel (ARI): "Contribution of Globular Clusters to the Build-up of the Galactic Halo"
Editor: T. Lisker
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