The Low-Mass Stellar Content of Westerlund 1

Copy Link

The low-mass stellar content of Westerlund 1 Morten Andersen (Gemini South) Galactic young massive star clusters • Connection between local and global SF. • Can resolve the stellar populations to low masses • Star counts instead of integrated properties • Directly measure the IMF The IMF in resolved massive clusters Only scale-free part probed Westerlund 1 • Distance of ~4 Kpc, age 3-5 Myr • Total mass estimated to be 50000 Msun • High foreground extinction • Best opportunity for resolving the low mass content in a young massive cluster • HST J (F125W) and H (F160W) band imaging Westerlund 1 from ground 5pc 4.5’ SOfI JHK, Brandner et al. 2007, Gennaro et al. Early lessons • Probe down to ~3 Msun, normal (Salpeter) IMF • Total mass of ~50000 Msun assuming standard IMF • Mass segregated, at least for high masses • Elliptical cluster • Currently difficult to improve from the ground Westerlund 1 with HST 5pc 4.5’ WFC3 F125W, F160W. Andersen et al. 2016 Color-magnitude diagrams Andersen et al. 2016 Foreground population Andersen et al. 2016 Red Clump Andersen et al. 2016 Background contamination Andersen et al. 2016 Cluster main sequence MS/PMS turn-on Andersen et al. 2016 Field star subtraction Andersen et al. 2016 Mass Functions Log-normal fit below 1 Msun to the 50% completeness limit. Power-law fit above 1 Msun (Siess 4 Myr isochrone) Change of fit parameters as a function of radius M < 1 Msun, log-normal fits Comparable peak mass as the field. More narrow distribution Change of fit parameters as a function of radius M > 1 Msun Evidence for mass segregation out to 1.5-2 pc Andersen et al. 2016 The IMF of Westerlund 1: • Reach down to 0.2 Msun in outer parts • Log-normal fit provides results similar to the field • Evidence for M > 1 Msun mass segregated • Total mass of cluster (star counts) 50000 Msun Is Westerlund 1 bound? • Gas expulsion has already occurred • The most massive stars exploded. • Has this disrupted the cluster or will it survive? • Is it a light-weight globular cluster progenitor? • Radial vel. measurements provide vel. dispersion • Multi-epoch Magellan R~20000 spectra Radial velocity dispersion B supergiants Yellow hyper giants Yellow hyper giants Low velocity dispersion 2.1+3.4-0.9km/s Cottaar, Meyer, Andersen & Espinoza, A&A 2012 Consistent with cluster being bound Gemini GeMS/GSAOI K band: NGS configuration on the observed mosaic GSAOI (2.1 micron) vs HST (F125W) FOV 45”x60” Source detection: GSAOI (left), HST (right) Increased source counts mainly due to resolution.

Recommended publications

Astronomie in Theorie Und Praxis 8. Auflage in Zwei Bänden Erik Wischnewski

Astronomie in Theorie und Praxis 8. Auflage in zwei Bänden Erik Wischnewski Inhaltsverzeichnis 1 Beobachtungen mit bloßem Auge 37 Motivation 37 Hilfsmittel 38 Drehbare Sternkarte Bücher und Atlanten Kataloge Planetariumssoftware Elektronischer Almanach Sternkarten 39 2 Atmosphäre der Erde 49 Aufbau 49 Atmosphärische Fenster 51 Warum der Himmel blau ist? 52 Extinktion 52 Extinktionsgleichung Photometrie Refraktion 55 Szintillationsrauschen 56 Angaben zur Beobachtung 57 Durchsicht Himmelshelligkeit Luftunruhe Beispiel einer Notiz Taupunkt 59 Solar-terrestrische Beziehungen 60 Klassifizierung der Flares Korrelation zur Fleckenrelativzahl Luftleuchten 62 Polarlichter 63 Nachtleuchtende Wolken 64 Haloerscheinungen 67 Formen Häufigkeit Beobachtung Photographie Grüner Strahl 69 Zodiakallicht 71 Dämmerung 72 Definition Purpurlicht Gegendämmerung Venusgürtel Erdschattenbogen 3 Optische Teleskope 75 Fernrohrtypen 76 Refraktoren Reflektoren Fokus Optische Fehler 82 Farbfehler Kugelgestaltsfehler Bildfeldwölbung Koma Astigmatismus Verzeichnung Bildverzerrungen Helligkeitsinhomogenität Objektive 86 Linsenobjektive Spiegelobjektive Vergütung Optische Qualitätsprüfung RC-Wert RGB-Chromasietest Okulare 97 Zusatzoptiken 100 Barlow-Linse Shapley-Linse Flattener Spezialokulare Spektroskopie Herschel-Prisma Fabry-Pérot-Interferometer Vergrößerung 103 Welche Vergrößerung ist die Beste? Blickfeld 105 Lichtstärke 106 Kontrast Dämmerungszahl Auflösungsvermögen 108 Strehl-Zahl Luftunruhe (Seeing) 112 Tubusseeing Kuppelseeing Gebäudeseeing Montierungen 113 Nachführfehler
"#$%&'() + '', %-./0$%)%1 2 ()3 4&(5' 456')5'

rs uvvwxyuzyws { yz|z|} rsz}~suzywsu}u~w vz~wsw 456789@A C 99D 7EFGH67A7I P @AQ R8@S9 RST9AS9 UVWUX `abcdUVVe fATg96GTHP7Eh96HE76QGiT69pf q rAS76876@HTAs tFR u Fv wxxy @AQ 4FR 4u Fv wxxy UVVe abbc d dbdc e f gc hi` ij ad bch dgcadabdddc c d ac k lgbc bcgb dmg agd g` kg bdcd dW dd k bg c ngddbaadgc gabmob nb boglWad g kdcoddog kedgcW pd gc bcogbpd kb obpcggc dd kfq` UVVe c iba ! " #$%& $' ())01023 Book of Abstracts – Table of Contents Welcome to the European Week of Astronomy & Space Science ...................................................... iii How space, and a few stars, came to Hatfield ............................................................................... v Plenary I: UK Solar Physics (UKSP) and Magnetosphere, Ionosphere and Solar Terrestrial (MIST) ....... 1 Plenary II: European Organisation for Astronomical Research in the Southern Hemisphere (ESO) ....... 2 Plenary III: European Space Agency (ESA) .................................................................................. 3 Plenary IV: Square Kilometre Array (SKA), High-Energy Astrophysics, Asteroseismology ................... 4 Symposia (1) The next era in radio astronomy: the pathway to SKA .............................................................. 5 (2) The standard cosmological models - successes and challenges .................................................. 17 (3) Understanding substellar populations and atmospheres: from brown dwarfs to exo-planets .......... 28 (4) The life cycle of dust ...........................................................................................................
$Unlocking Galactic Wolf-Rayet Stars with $\Textit {Gaia} $ DR2 II: Cluster$

Unlocking Galactic Wolf-Rayet Stars with $\Textit {Gaia} $ DR2 II: Cluster

MNRAS 000,1{19 (2019) Preprint 7 May 2020 Compiled using MNRAS LATEX style file v3.0 Unlocking Galactic Wolf-Rayet stars with Gaia DR2 II: Cluster and Association membership Gemma Rate,? Paul A. Crowther, Richard J. Parkery Department of Physics and Astronomy, University of Sheffield, Sheffield, S3 7RH, UK Accepted XXX. Received YYY; in original form ZZZ ABSTRACT Galactic Wolf-Rayet (WR) star membership of star forming regions can be used to constrain the formation environments of massive stars. Here, we utilise Gaia DR2 parallaxes and proper motions to reconsider WR star membership of clusters and associations in the Galactic disk, supplemented by recent near-IR studies of young massive clusters. We find that only 18{36% of 553 WR stars external to the Galac- tic Centre region are located in clusters, OB associations or obscured star-forming regions, such that at least 64% of the known disk WR population are isolated, in contrast with only 13% of O stars from the Galactic O star Catalogue. The fraction located in clusters, OB associations or star-forming regions rises to 25{41% from a global census of 663 WR stars including the Galactic Centre region. We use simu- lations to explore the formation processes of isolated WR stars. Neither runaways, nor low mass clusters, are numerous enough to account for the low cluster member- ship fraction. Rapid cluster dissolution is excluded as mass segregation ensures WR stars remain in dense, well populated environments. Only low density environments consistently produce WR stars that appeared to be isolated during the WR phase.
Spatial Distribution of Galactic Wolf–Rayet Stars and Implications for the Global Population

MNRAS 447, 2322–2347 (2015) doi:10.1093/mnras/stu2525 Spatial distribution of Galactic Wolf–Rayet stars and implications for the global population C. K. Rosslowe‹ andP.A.Crowther Department of Physics and Astronomy, University of Sheffield, Hicks Building, Hounsfield Road, S3 7RH, UK Accepted 2014 November 26. Received 2014 November 26; in original form 2014 September 5 ABSTRACT We construct revised near-infrared absolute magnitude calibrations for 126 Galactic Wolf– Rayet (WR) stars at known distances, based in part upon recent large-scale spectroscopic surveys. Application to 246 WR stars located in the field permits us to map their Galactic distribution. As anticipated, WR stars generally lie in the thin disc (∼40 pc half-width at half- maximum) between Galactocentric radii 3.5–10 kpc, in accordance with other star formation tracers. We highlight 12 WR stars located at vertical distances of ≥300 pc from the mid-plane. Analysis of the radial variation in WR subtypes exposes a ubiquitously higher NWC/NWN ratio than predicted by stellar evolutionary models accounting for stellar rotation. Models for non- rotating stars or accounting for close binary evolution are more consistent with observations. We consolidate information acquired about the known WR content of the Milky Way to build a simple model of the complete population. We derive observable quantities over a range of wavelengths, allowing us to estimate a total number of 1900 ± 250 Galactic WR stars, implying an average duration of ∼ 0.4 Myr for the WR phase at the current Milky Way star formation rate. Of relevance to future spectroscopic surveys, we use this model WR population to predict follow-up spectroscopy to KS 17.5 mag will be necessary to identify 95 per cent of Galactic WR stars.
Resolving the Low-Mass Content of Westerlund 1 Using MCAO

Resolving the low-mass content of Westerlund 1 using MCAO M. Andersena, B. Neichelb, A. Bernardb, and V. Garrela aGemini Observatories, Casilla 603 La Silla, Chile bAix Marseille Université,CNRS, LAM (Laboratoire d'Astrophysique de Marseille) UMR 7326, 13388 Marseille, France ABSTRACT We present deep Ks band Gemini GeMS/GSAOI observations of Westerlund 1, the most massive young Galactic star cluster known. The high spatial resolution combined with a relatively stable point spread function across a large field of view provide unique possibilities to resolve the low-mass content of the cluster. We show that the clean point spread function is crucial in handling the source detection in this crowded field suffering extremely high contrast from the brightest hypergiants in the cluster to faint brown dwarfs. Keywords: star clusters: Westerlund 1, Initial Mass Function, Photometry, MCAO, Laser Guide Star Systems 1. INTRODUCTION Much progress has been made in the last decades in our understanding of low-mass star forming regions. Detailed observations of individual objects have made it possible to characterise them in detail and to determine the star formation history and the impact of environment. 4 Similar studies of massive star clusters (more than 10 M ) are much less detailed. However, they differ fundamentally from nearby regions in terms of their central densities and large content of massive stars that may have influenced the star formation process within the cluster. These clusters are rare and the nearest ones known are an order of magnitude more distant than the nearby low-mass regions. This, together with their higher densities, means that high spatial resolution observations are necessary to resolve the low-mass content of the clusters.
Study of Globular Cluster Sources Using Erass1 Data

Study of Globular Cluster Sources using eRASS1 data Bachelorarbeit aus der Physik Vorgelegt von Roman Laktionov 27. April 2021 Dr. Karl Remeis-Sternwarte Friedrich-Alexander-Universität Erlangen-Nu¨rnberg Betreuerin: Prof. Dr. Manami Sasaki Abstract Due to the high stellar density in globular clusters (GCs), they provide an ideal envi- ronment for the formation of X-ray luminous objects, e.g. cataclysmic variables and low-mass X-ray binaries. Those X-ray sources have, in the advent of ambitious observa- tion campaigns like the eROSITA mission, become accessible for extensive population studies. During the course of this thesis, X-ray data in the direction of the Milky Way's GCs was extracted from the eRASS1 All-Sky Survey and then analyzed. The first few chap- ters serve to provide an overview on the physical properties of GCs, the goals of the eROSITA mission and the different types of X-ray sources. Afterwards, the methods and results of the analysis will be presented. Using data of the eRASS1 survey taken between December 13th, 2019 and June 11th, 2020, 113 X-ray sources were found in the field of view of 39 GCs, including Omega Cen- tauri, 47 Tucanae and Liller 1. A Cross-correlation with optical/infrared catalogs and the subsequent analysis of various diagrams enabled the identification of 6 foreground stars, as well as numerous background candidates and stellar sources. Furthermore, hardness ratio diagrams were used to select 16 bright sources, possibly of GC origin, for a spectral analysis. By marking them in X-ray and optical images, it was concluded that 6 of these sources represent the bright central emission of their host GC, while 10 are located outside of the GC center.
A 3Mm ALMA Census of the Massive Cluster Westerlund 1 1 2 1 3 4 5 6 2 D

A 3mm ALMA census of the massive cluster Westerlund 1 D. Fenech1, J. Clark2, R. Prinja1, S. Dougherty3, F. NaJarro4, I. Negueruela5, A. Richards6 and B. Ritchie2 1Department of Physics and Astronomy, University College London, U.K.; 2School of Physical Science, The Open University, UK; 3Dominion Radio Astrophysical Observatory, National Research Council Canada; 4Departamento de Física, Ingenaría de Sistemas y Teoría de la Señal, Universidad de Alicante, Spain; 5Departamento de Astrofísica, Centro de Astrobiología, (CSIC-INTA) Spain; 6JBCA, University of Manchester & MERLIN/VLBI National Facility, JBO,U.K. Westerlund 1 Massive stars Cool super-/hypergiants Westerlund 1 (Wd1) is one of the first examples of a super star cluster within our Despite their rarity, massive stars play a major role in galactic evolution. They deposit large amounts of Galaxy and contains a population of co-eval massive stars. Located at a distance of Yellow hypergiants (YHGs) and red supergiants (RSGs) are of particular chemically enriched material, energy and ionising radiation into their environment and dominate the ~5 kpc, Wd1 was discovered by Westerlund in 1961 (Westerlund, 1961,PASP, 73, interest as they are believed to shed mass at suffucent rates to profoundly integrated galactic spectra in the UV and IR regimes (via re-radiation). However, the lives of massive stars 51). However, the large extinction towards Wd1 (Av~11 mag) meant that few affect a stars evolution in spite of spending relatively little time in this are still poorly understood. observations were made of the cluster until relatively recently when radio images phase. Mass-loss is considered a critical factor in the evolutionary pathway of massive stars and consequently the revealed a large number of radio sources (Dougherty et al.
Annual Report 2007 ESO

ESO European Organisation for Astronomical Research in the Southern Hemisphere Annual Report 2007 ESO European Organisation for Astronomical Research in the Southern Hemisphere Annual Report 2007 presented to the Council by the Director General Prof. Tim de Zeeuw ESO is the pre-eminent intergovernmental science and technology organisation in the field of ground-based astronomy. It is supported by 13 countries: Belgium, the Czech Republic, Denmark, France, Finland, Germany, Italy, the Netherlands, Portugal, Spain, Sweden, Switzerland and the United Kingdom. Further coun- tries have expressed interest in member- ship. Created in 1962, ESO provides state-of- the-art research facilities to European as- tronomers. In pursuit of this task, ESO’s activities cover a wide spectrum including the design and construction of world- class ground-based observational facili- ties for the member-state scientists, large telescope projects, design of inno- vative scientific instruments, developing new and advanced technologies, further- La Silla. ing European cooperation and carrying out European educational programmes. One of the most exciting features of the In 2007, about 1900 proposals were VLT is the possibility to use it as a giant made for the use of ESO telescopes and ESO operates the La Silla Paranal Ob- optical interferometer (VLT Interferometer more than 700 peer-reviewed papers servatory at several sites in the Atacama or VLTI). This is done by combining the based on data from ESO telescopes were Desert region of Chile. The first site is light from several of the telescopes, al- published. La Silla, a 2 400 m high mountain 600 km lowing astronomers to observe up to north of Santiago de Chile.
Magnetars Unleash Mammoth Bursts of Energy, but How and Why? Astronomers Are Working to Understand These Bizarre Stellar Objects

In search of the galaxy’s magnetic Magnetars unleash mammoth bursts of energy, but how and why? Astronomers are working to understand these bizarre stellar objects. By Steve Nadis monsters n 1987, when Robert Duncan and Chris- the 5-day event, seemingly lumped in the objects constitute a distinct class of pul- Blasts from beyond IN a magNetar’S gIaNt flareS, magnetic field lines break and reconnect, releasing a burst of topher Thompson first contemplated the fringe category. sars. They are rapidly spinning, intensely Scientists’ now believe magnetars exist energy. This process resembles solar-flare formation, except magnetars’ flares are much more existence of ultramagnetized neutron Six years later, in 2004, colleagues magnetic neutron stars — dense remnants because of a confluence of theory and obser- powerful. Don Dixon for Astronomy stars (later dubbed “magnetars”), they finally recognized Duncan and Thompson of massive stars that expired in fiery vational data from some of nature’s most had a hard time convincing themselves (now at the University of Texas and the supernova blasts. impressive high-energy displays. For astron- magnetic field of about a million billion powerful flare from outside our solar sys- I that the notion made sense. Five years University of Toronto, respectively) for Armed with this knowledge, researchers omers, says Thompson, the turning point (1015) gauss. (Earth’s magnetic field reaches tem astronomers had ever recorded. In later, when they got their first opportunity their theoretical work on magnetars.
January 2019 BRAS Newsletter

Monthly Meeting January 14th at 7PM at HRPO (Monthly meetings are on 2nd Mondays, Highland Road Park Observatory). Speaker: Jim Gutierrez, Sunspots, Hot Spots and Relativity What's In This Issue? President’s Message Secretary's Summary Outreach Report Astrophotography Group Comet and Asteroid News Light Pollution Committee Report “Free The Milky Way” Campaign Recent BRAS Forum Entries Messages from the HRPO Science Academy Friday Night Lecture Series Globe at Night Adult Astronomy Courses Total Lunar Eclipse Observing Notes – Ara – The Alter & Mythology Like this newsletter? See PAST ISSUES online back to 2009 Visit us on Facebook – Baton Rouge Astronomical Society Newsletter of the Baton Rouge Astronomical Society January 2019 © 2019 President’s Message First off, I thank you for placing your trust in me for another year. Another thanks goes out to Scott Cadwallader and John R. Nagle for fixing the Library Telescope. The telescope was missing a thumbnut witch Orion Telescope replaced, Scott and John, put the thumbnut back on and reset the collimation. Let’s don’t forget the Total Lunar Eclipse coming up this January 20th. See HRPO announcement below. We are planning 2019 and hope to have an enjoyable year for our members. I’d like to find more opportunity to point our telescopes at the night sky. If there is anything you’d like to see, do, or wish to offer let us know. Our webmaster has set up a private forum: "BRAS Members Only" Group/Section to the "Baton Rouge Astronomical Society Forum" (http://www.brastro.org/phpBB3/). The plan is to use this Group/Section to get additional information to members and get feedback from members without the need of flooding everyone's inbox.
Miljenko Čemeljić, CAMK, Warsaw & ASIAA, Taiwan

arXiv:2012.08550 Miljenko Čemeljić, CAMK, Warsaw & ASIAA, Taiwan Miljenko Čemeljić, CAMK Journal Club, March, 2021, Warsaw Outline -Hypergiants? -VY Canis Majoris -Possible implications on the explanation of the recent dimming of Betelgeuse. Miljenko Čemeljić, CAMK Journal Club, March, 2021, Warsaw Hypergiants -Hypergiants: how giant are they? -At the beginning of the article is written that if VY Cma, with radius about 1420 R_sun, would be in place of our Sun, it would reach to Jupiter. Jupiter? I remembered “giants, e.g. Antares, would reach to Mars”, this one ... Jupiter?! Other supergiants are Westerlund 1-26, WOH G64, with about 1200 and 1500 R_sun, and Stephenson 2-18 with about 2500 R_sun-it would reach to Saturn! Light travelling around the equator of VY CMa star would take 6 hours, compared to 14.5 seconds for the Sun. It is not at all that “obvious” for me that gaseous spheres can be THAT big. I did not remember it from the HR diagrams I saw. “Space is big. You just won't believe how vastly, hugely, mind-bogglingly big it is. I mean, you may think it's a long way down the road to the chemist's, but that's just peanuts to space.” ― Douglas Adams, “The Hitchhiker's Guide to the Galaxy” Supergiants in HR diagram Radius of the Sun is about 695,700 km --> diameter is of the order of 1 million km. Distance Earth-Moon is 384 000 km. Hypergiants? Supergiants in HR diagram About 90 percent of the stars in the universe exist along Main sequence line at one time in their lives, when they still fuse hydrogen to helium.
A Chandra X-Ray Study of the Young Star Cluster NGC 6231: Low-Mass Population and Initial Mass Function? F

A&A 596, A82 (2016) Astronomy DOI: 10.1051/0004-6361/201629029 & c ESO 2016 Astrophysics A Chandra X-ray study of the young star cluster NGC 6231: low-mass population and initial mass function? F. Damiani, G. Micela, and S. Sciortino INAF−Osservatorio Astronomico di Palermo G. S. Vaiana, Piazza del Parlamento 1, 90134 Palermo, Italy e-mail: [email protected] Received 31 May 2016 / Accepted 26 July 2016 ABSTRACT Context. NGC 6231 is a massive young star cluster, near the center of the Sco OB1 association. While its OB members are well studied, its low-mass population has received little attention. We present high-spatial resolution Chandra ACIS-I X-ray data, where we detect 1613 point X-ray sources. Aims. Our main aim is to clarify global properties of NGC 6231 down to low masses through a detailed membership assessment, and to study the cluster stars’ spatial distribution, the origin of their X-ray emission, the cluster age and formation history, and initial mass function. Methods. We use X-ray data, complemented by optical and IR data, to establish cluster membership. The spatial distribution of dif- ferent stellar subgroups also provides highly significant constraints on cluster membership, as does the distribution of X-ray hardness. We perform spectral modelling of group-stacked X-ray source spectra. Results. We find a large cluster population down to ∼0.3 M (complete to ∼1 M ), with minimal non-member contamination, with a definite age spread (1−8 Myr) for the low-mass PMS stars. We argue that low-mass cluster stars also constitute the majority of the few hundreds unidentified X-ray sources.