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A candidate diffuse stellar substructure was previously reported in the halo of the nearby dwarf starburst galaxy NGC 4449 by Karachentsev et al. We map and analyze this feature using a unique combination of deep integrated-light images…

We use the Stripe 82 proper motion catalogue of Bramich et al. (2008) to study the kinematics of Galactic disk stars in the solar neighborhood. We select samples of dwarf stars with reliable spectra and proper motions. They have cylindrical…

星系天体物理 · 物理学 2012-02-08 Martin C. Smith , S. Hannah Whiteoak , N. W. Evans

We present a revised and expanded catalog of satellite galaxies of a set of isolated spiral galaxies similar in luminosity to the Milky Way. This sample of 115 satellites, 69 of which were discovered in our multifiber redshift survey, is…

天体物理学 · 物理学 2009-09-25 Dennis Zaritsky , Rodney Smith , Carlos Frenk , Simon D. M. White

Blue straggler, which are stars that appear to be younger than they should be, are an important population of unusual stars in both stellar clusters and the halo field of the Galaxy. Most formation scenarios evoke either stellar collisions…

太阳与恒星天体物理 · 物理学 2015-05-18 A. Tillich , N. Przybilla , R. -D. Scholz , U. Heber

The formation mechanism of the hot gaseous halo associated with the Milky Way Galaxy is still under debate. We report new observational constraints on the gaseous halo using 107 lines-of-sight of the Suzaku X-ray observations at…

星系天体物理 · 物理学 2018-08-08 Shinya Nakashima , Yoshiyuki Inoue , Noriko Yamasaki , Yoshiaki Sofue , Jun Kataoka , Kazuhiro Sakai

New spectroscopic observations of the halo hyper-velocity star candidate SDSS J121150.27+143716.2 ($V=17.92$ mag) revealed a cool companion to the hot subdwarf primary. The components have a very similar radial velocity and their absolute…

太阳与恒星天体物理 · 物理学 2016-04-13 Péter Németh , Eva Ziegerer , Andreas Irrgang , Stephan Geier , Felix Fürst , Thomas Kupfer , Ulrich Heber

We present evidence for a metal-poor, [Fe/H]$\sim-1.4$ $\sigma$=0.2 dex, stellar halo component detectable at radii from 10 kpc to 70 kpc, in our nearest giant spiral neighbor, the Andromeda galaxy. This metal-poor sample underlies the…

天体物理学 · 物理学 2008-11-26 S. C. Chapman , R. Ibata , G. F. Lewis , A. M. N. Ferguson , M. Irwin , A. McConnachie , N. Tanvir

Within a cosmological hydrodynamical simulation, we form a disc galaxy with sub- components which can be assigned to a thin stellar disc, thick disk, and a low mass stellar halo via a chemical decomposition. The thin and thick disc…

We use the \texttt{GRUMPY} galaxy formation model based on a suite of zoom-in, high-resolution, dissipationless $\Lambda$ Cold Dark Matter ($\Lambda$CDM) simulations of the Milky Way (MW) sized haloes to examine total matter density within…

星系天体物理 · 物理学 2023-08-02 Andrey Kravtsov , Zewei Wu

The recent discovery of thousands of ultra diffuse galaxies (UDGs) in nearby galaxy clusters has opened a new window into the process of galaxy formation and evolution. Several scenarios have been proposed to explain the formation history…

星系天体物理 · 物理学 2017-12-06 Cristóbal Sifón , Remco F. J. van der Burg , Henk Hoekstra , Adam Muzzin , Ricardo Herbonnet

Abridged: We estimate the distances to ~48 million stars detected by the Sloan Digital Sky Survey and map their 3D number density distribution in 100 < D < 20 kpc range over 6,500 deg^2 of sky. The data show strong evidence for a Galaxy…

Gamma-ray pulsar halos are ideal indicators of cosmic-ray propagation in localized regions of the Galaxy and electron injection from pulsar wind nebulae. HESS~J1831$-$098 is a candidate pulsar halo observed by both H.E.S.S. and HAWC…

高能天体物理现象 · 物理学 2022-12-28 Kun Fang , Shao-Qiang Xi , Li-Zhuo Bao , Xiao-Jun Bi , En-Sheng Chen

Galaxies are thought to grow through accretion; as less massive galaxies are disrupted and merge over time, their debris results in diffuse, clumpy stellar halos enveloping the central galaxy. Here we present a study of the variation in the…

星系天体物理 · 物理学 2016-10-19 Allison Merritt , Pieter van Dokkum , Roberto Abraham , Jielai Zhang

We construct a mass model for the spiral lens galaxy 2237+0305, at redshift z_l=0.04, based on gravitational-lensing constraints, HI rotation, and new stellar-kinematic information, based on data taken with the ESI spectrograph on the 10m…

天体物理学 · 物理学 2015-05-13 C. M. Trott , T. Treu , L. V. E. Koopmans , R. L. Webster

We use high-quality optical rotation curves of 9 low-luminosity disk galaxies to obtain the velocity profile of the surrounding dark matter halos. We find that they increase linearly with radius at least out to the stellar disk edge,…

天体物理学 · 物理学 2009-10-31 A. Borriello , P. Salucci

We use KiDS weak lensing data to measure variations in mean halo mass as a function of several key galaxy properties (namely: stellar colour, specific star formation rate, Sersic index, and effective radius) for a volume-limited sample of…

We estimate the 3D density profile of the Galactic dark matter (DM) halo within $r \lesssim 30$ kpc from the Galactic centre by using the astrometric data for halo RR Lyrae stars from Gaia DR2. We model both the stellar halo distribution…

星系天体物理 · 物理学 2021-10-20 Kohei Hattori , Monica Valluri , Eugene Vasiliev

We use \texttt{GRUMPY}, a simple regulator-type model for dwarf galaxy formation and evolution, to forward model the dwarf galaxy satellite population of the Milky Way (MW) using the Caterpillar zoom-in simulation suite. We show that…

星系天体物理 · 物理学 2022-09-14 Viraj Manwadkar , Andrey Kravtsov

Aims. Neutron stars (NSs) produced in the Milky Way are supposedly ten to the eighth - ten to the ninth, of which only $\sim 2 \times 10^{3}$ are observed. Constraining the phase space distribution of NSs may help to characterize the yet…

星系天体物理 · 物理学 2015-05-14 N. Sartore , E. Ripamonti , A. Treves , R. Turolla

In this paper we review the main and the most recent evidence for the presence of a core radius in the distribution of the dark matter around spiral galaxies. Their rotation curves, coadded according to the galaxy luminosity, conform to an…

天体物理学 · 物理学 2007-05-23 Paolo Salucci , Annamaria Borriello