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تسجيل مستخدم جديدGlobular Cluster Systems and X-Ray Atmospheres in Galaxies
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We compare the empirical relationships between the mass of a galaxys globular system M_GCS, the gas mass in the hot X-ray atmosphere M_X within a fiducial radius of 5 r_e, the total gravitational mass M_grav within 5 r_e, and lastly the total halo mass M_h calibrated from weak lensing. We use a sample of 45 early-type galaxies (ETGs) for which both GCS and X-ray data are available; all the galaxies in our sample are relatively high-mass ones with M_h > 10^12 M_sun. We find that M_X ~ M_h^1.0, similar to the previously known scaling relation M_GCS ~ M_h^1.0. Both components scale much more steeply than the more well known dependence of total stellar mass M_star ~ M_h^0.3 for luminous galaxies. These results strengthen previous suggestions that feedback had little effect on formation of the globular cluster system. The current data are also used to measure the relative mass fractions of baryonic matter and dark matter (DM) within 5 r_e. We find a strikingly uniform mean of <f_DM> = 0.83 with few outliers and an rms scatter of +-0.07. This result is in good agreement with two recent suites of hydrodynamic galaxy formation models.
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We analyse the globular cluster (GC) systems of a sample of 15 massive, compact early-type galaxies (ETGs), 13 of which have already been identified as good relic galaxy candidates on the basis of their compact morphologies, old stellar populations a
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Ultra-diffuse galaxies (UDGs) are unusual galaxies with low luminosities, similar to classical dwarf galaxies, but sizes up to $sim!5$ larger than expected for their mass. Some UDGs have large populations of globular clusters (GCs), something unexpec
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Globular clusters are compact, gravitationally bound systems of up to a million stars. The GCs in the Milky Way contain some of the oldest stars known, and provide important clues to the early formation and continuing evolution of our Galaxy. More ge
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pc that have estimates of the globular cluster (GC) specific frequency (SN) reported in the literature. As such, we are able to directly classify X-ray-detected sources as being either coincident with unrelated background/foreground objects, GCs, or sources that are within the fields of the galaxy targets. We model the GC and field LMXB population XLFs for all galaxies separately, and then construct global models characterizing how the LMXB XLFs vary with galaxy stellar mass and SN. We find that our field LMXB XLF models require a component that scales with SN, and has a shape consistent with that found for the GC LMXB XLF. We take this to indicate that GCs are seeding the galactic field LMXB population, through the ejection of GC-LMXBs and/or the diffusion of the GCs in the galactic fields themselves. However, we also find that an important LMXB XLF component is required for all galaxies that scales with stellar mass, implying that a substantial population of LMXBs are formed in situ, which dominates the LMXB population emission for galaxies with SN < 2. For the first time, we provide a framework quantifying how directly-associated GC LMXBs, GC-seeded LMXBs, and in-situ LMXBs contribute to LMXB XLFs in the broader early-type galaxy population.
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