A Deep View into the Nucleus of the Sagittarius Dwarf Spheroidal Galaxy with MUSE. I. Data and Stellar Population Characterization

20 Jan

[2019ApJ…886…57A]  Alfaro-Cuello, M.; Kacharov, N.; Neumayer, N.; Lützgendorf, N.; Seth, A. C.; Böker, T.; Kamann, S.; Leaman, R.; van de Ven, G.; Bianchini, P.; Watkins, L. L.; Lyubenova, M.

The center of the Sagittarius dwarf spheroidal galaxy (Sgr dSph) hosts a nuclear star cluster (NSC), M54, which is the only galaxy nucleus that can be resolved into individual stars at optical wavelengths. It is thus a key target for understanding the formation of NSCs and their relation to globular clusters (GCs). We present a large Multi-Unit Spectroscopic Explorer data set that covers M54 out to ∼2.5 half-light radius, from which we extracted the spectra of ∼6600 cluster member stars.

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The Impact of Cosmic Rays on the Sensitivity of JWST/NIRSpec

20 Jan

[2019PASP..131i4503G]  Giardino, Giovanna; Birkmann, Stephan; Robberto, Massimo; Ferruit, Pierre; Rauscher, Bernard J.; Sirianni, Marco; Alves de Oliveira, Catarina; Boeker, Torsten; Luetzgendorf, Nora; te Plate, Maurice; Puga, Elena; Rawle, Tim

The focal plane of the Near Infrared Spectrograph (NIRSpec) instrument on board the James Webb Space Telescope (JWST) is equipped with two Teledyne H2RG near-IR detectors, state-of-the-art HgCdTe sensors with excellent noise performance. Once JWST is in space, however, the noise level in NIRSpec exposures will be affected by the cosmic ray (CR) fluence at the JWST orbit and our ability to detect CR hits and to mitigate their effect.

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Massive and Evolved Stars with the ngVLA

20 Jan

[2018ASPC..517..389M]  Maccarone, T. J.; Caballero-Nieves, S.; Smith, N.; Lützgendorf, N.

The next generation Very Large Array will have excellent sensitivity for detecting the thermal emission from massive stars and from red giants. This will allow direct imaging of the winds for a large number of hot massive stars. It will also allow using the radio emission for the massive stars as a way to detect stars to allow high resolution measurements can be made, even with large extinction.

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A MODEST review

20 Jan

2018ComAC…5….2V]  Varri, Anna Lisa; Cai, Maxwell Xu; Concha-Ramírez, Francisca; Dinnbier, František; Lützgendorf, Nora; Pavlík, Václav; Rastello, Sara; Sollima, Antonio; Wang, Long; Zocchi, Alice

We present an account of the state of the art in the fields explored by the research community invested in “Modeling and Observing DEnse STellar systems”. For this purpose, we take as a basis the activities of the MODEST-17 conference, which was held at Charles University, Prague, in September 2017.

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An Upper Limit on the Mass of a Central Black Hole in the Large Magellanic Cloud from the Stellar Rotation Field

20 Jan

[2017ApJ…846…14B]  Boyce, H.; Lützgendorf, N.; van der Marel, R. P.; Baumgardt, H.; Kissler-Patig, M.; Neumayer, N.; de Zeeuw, P. T.

We constrain the possible presence of a central black hole (BH) in the center of the Large Magellanic Cloud. This requires spectroscopic measurements over an area of the order of a square degree, due to the poorly known position of the kinematic center. Such measurements are now possible with the impressive field of view of the Multi Unit Spectroscopic Explorer (MUSE) on the ESO Very Large Telescope.

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Masses and scaling relations for nuclear star clusters, and their co-existence with central black holes

20 Jan

[2016MNRAS.457.2122G]  Georgiev, Iskren Y.; Böker, Torsten; Leigh, Nathan; Lützgendorf, Nora; Neumayer, Nadine

Galactic nuclei typically host either a Nuclear Star Cluster (NSC, prevalent in galaxies with masses 1010M) or a Massive Black Hole (MBH, common in galaxies with masses 1012M). In the intermediate mass range, some nuclei host both a NSC and a MBH. In this paper, we explore scaling relations between NSC mass (MNSC) and host galaxy total stellar mass (M,gal) using a large sample of NSCs in late- and early-type galaxies, including a number of NSCs harboring a MBH. Continue reading

Stellar winds near massive black holes – the case of the S-stars

20 Jan

[2016MNRAS.456.3645L]  Lützgendorf, N.; Helm, E. van der; Pelupessy, F. I.; Portegies Zwart, S.

The Galactic Centre provides a unique laboratory to study the interaction of a supermassive black hole (SMBH) with its gaseous and stellar environment. Simulations to determine the accretion of stellar winds from the surrounding O-stars on to the black hole have been performed earlier, but in those the presence of the S-star system was ignored. The S-stars are a group of young massive B-stars in relatively close orbits around the black hole. Continue reading

MOCCA code for star cluster simulations – IV. A new scenario for intermediate mass black hole formation in globular clusters

20 Jan

[2015MNRAS.454.3150G]  Giersz, Mirek; Leigh, Nathan; Hypki, Arkadiusz; Lützgendorf, Nora; Askar, Abbas

We discuss a new scenario for the formation of intermediate mass black holes (IMBHs) in dense star clusters. In this scenario, IMBHs are formed as a result of dynamical interactions of hard binaries containing a stellar-mass black hole (BH), with other stars and binaries. We discuss the necessary conditions to initiate the process of intermediate mass BH formation and the influence of an IMBH on the host global globular cluster (GC) properties. We discuss two scenarios for IMBH formation. Continue reading

KMOS view of the Galactic centre. I. Young stars are centrally concentrated

20 Jan

[2015A&A…584A…2F]  Feldmeier-Krause, A.; Neumayer, N.; Schödel, R.; Seth, A.; Hilker, M.; de Zeeuw, P. T.; Kuntschner, H.; Walcher, C. J.; Lützgendorf, N.; Kissler-Patig, M.

Context. The Galactic centre hosts a crowded, dense nuclear star cluster with a half-light radius of 4 pc. Most of the stars in the Galactic centre are cool late-type stars, but there are also ≳100 hot early-type stars in the central parsec of the Milky Way. These stars are only 3-8 Myr old.
Aims: Our knowledge of the number and distribution of early-type stars in the Galactic centre is incomplete. Only a few spectroscopic observations have been made beyond a projected distance of 0.5 pc of the Galactic centre. The distribution and kinematics of early-type stars are essential to understand the formation and growth of the nuclear star cluster. Continue reading