Globular clusters in NGC147, 185, and 205

2006 ◽  
Vol 2 (S237) ◽  
pp. 473-473
Author(s):  
M. E. Sharina ◽  
V. L. Afanasiev ◽  
T. H. Puzia
Keyword(s):  
Absorption Line ◽  
Globular Clusters ◽  
Building Blocks ◽  
Chemical Compositions ◽  
Early Type ◽  
Central Regions ◽  
Low Mass ◽  
Almost All ◽  
Living Objects ◽  
Halo Population

AbstractStudying the chemical compositions and color-magnitude diagrams of globular clusters in the nearby low-mass galaxies is critical to compare properties of these long-living objects situated in galaxies of different type and mass, and to establish the role of dwarf galaxies as building blocks of massive early-type and spiral galaxies. We present measurements of ages, metallicities and [α/Fe] ratios for 16 globular clusters (GC) in NGC147, NGC185, and NGC205 and for the central regions of the diffuse galaxy light in NGC185, and NGC205, based on measurements of absorption line indices as defined by the Lick standard system in spectra obtained with the SCORPIO multi-slit spectrograph at the 6-m telescope of the Russian Academy of Sciences. We include in our analysis high-quality HST/WFPC2 photometry of individual stars in the GGs to investigate the influence of their horizontal branch (HB) morphology on the spectroscopic analysis. The HB morphologies for our sample GCs follow the same behavior with metallicity as younger halo Galactic globular clusters. We show that it is unlikely that they bias our spectroscopic age estimates based on Balmer absorption-line indices. Almost all our sample GCs appear to be old (T > 8 Gyr) and metal-poor ([Z/H]<−1.1). We find that most of the GCs in the studied galaxies are weakly or not α-enhanced, in contrast to the population of GCs in nearby early-type galaxies, and to the halo population of GCs in M31 and Milky Way.

scholarly journals Globular clusters and the evolution of their multiple stellar populations

2015 ◽  
Vol 12 (S316) ◽  
pp. 328-333
Author(s):  
W. Chantereau ◽  
C. Charbonnel ◽  
G. Meynet
Keyword(s):  
Globular Clusters ◽  
Main Sequence ◽  
Chemical Properties ◽  
Stellar Populations ◽  
Chemical Compositions ◽  
Low Mass Stars ◽  
Sequence Band ◽  
Low Mass ◽  
Chemical Distribution ◽  
Host Stars

AbstractOur knowledge of the formation and early evolution of globular clusters (GCs) has been totally shaken with the discovery of the peculiar chemical properties of their long-lived host stars. Therefore, the interpretation of the observed Colour Magnitude Diagrams (CMD) and of the properties of the GC stellar populations requires the use of new stellar models computed with relevant chemical compositions. In this paper we use the grid of evolution models for low-mass stars computed by Chantereau et al. (2015) with the initial compositions of second-generation stars as predicted by the fast rotating massive stars scenario to build synthesis models of GCs. We discuss the implications of the assumed initial chemical distribution on 13 Gyr isochrones. We build population synthesis models to predict the fraction of stars born with various helium abundances in present day globular clusters (assuming an age of 13 Gyr). With the current assumptions, 61 % of stars on the main sequence are predicted to be born with a helium abundance in mass fraction, Yini, smaller than 0.3 and only 11 % have a Yini larger than 0.4. Along the horizontal branch, the fraction of stars with Yini inferior to 0.3 is similar to that obtained along the main sequence band (63 %), while the fraction of very He-enriched stars is significantly decreased (only 3 % with Yini larger than 0.38).

The range of UV upturn strengths in early-type galaxies can be caused by dissolved metal-rich Globular Clusters

2019 ◽  
Vol 14 (S351) ◽  
pp. 112-116
Author(s):  
Paul Goudfrooij
Keyword(s):  
Globular Clusters ◽  
Dynamical Evolution ◽  
Virgo Cluster ◽  
Host Galaxy ◽  
Early Type ◽  
Luminosity Functions ◽  
Central Regions ◽  
Specific Frequency ◽  
Uv Upturn

AbstractI summarize the scenario by Goudfrooij (2018) in which the bulk of the ultraviolet (UV) upturn of giant early-type galaxies (ETGs) is due to helium-rich stellar populations that formed in massive metal-rich globular clusters (GCs) and subsequently dissolved in the strong tidal field in the central regions of the massive host galaxy. These massive GCs are assumed to show UV upturns similar to those observed recently in M87, the central galaxy in the Virgo cluster of galaxies. Data taken from the literature reveals a strong correlation between the strength of the UV upturn and the specific frequency of metal-rich GCs in ETGs. Adopting a Schechter function parametrization of GC mass functions, simulations of long-term dynamical evolution of GC systems show that this correlation can be explained by variations in the characteristic truncation mass Mc such that Mc increases with ETG luminosity in a way that is consistent with observed GC luminosity functions in ETGs. These findings suggest that the nature of the UV upturn in ETGs and the variation of its strength among ETGs are causally related to that of helium-rich populations in massive GCs, rather than intrinsic properties of field stars in ETGs.

scholarly journals Globular Clusters, Dwarf Galaxies, and the Assembly of the M87 Halo

2015 ◽  
Vol 11 (S317) ◽  
pp. 153-158
Author(s):  
Eric W. Peng ◽  
Hong-Xin Zhang ◽  
Chengze Liu ◽  
Yiqing Liu
Keyword(s):  
Globular Clusters ◽  
Dwarf Galaxies ◽  
Galaxy Cluster ◽  
Virgo Cluster ◽  
Early Type ◽  
Massive Galaxies ◽  
Low Mass ◽  
Using Data ◽  
The Relationship ◽  
Negative Gradient

AbstractAt the center of the nearest galaxy cluster, the Virgo cluster, lies the massive cD galaxy, M87 (NGC 4486). Using data from the Next Generation Virgo Cluster Survey, we investigate the relationship between M87, its globular clusters (GCs), and satellite dwarf galaxies. We find that the kinematics of GCs and ultra-compact dwarfs (UCDs) are different, indicating that UCDs are not simply massive GCs. We also identify a morphological sequence of envelope fraction around UCDs correlated with cluster-centric distance that suggest UCDs are the result of tidal stripping. Lastly, we find that the [α/Fe] abundance ratios of low-mass early-type galaxies in Virgo exhibit a strong negative gradient within ~ 400 kpc of M87, where the galaxies closest to M87 have the highest values. These satellite galaxies are likely the surviving counterparts of accreted dwarfs that contribute stars to the metal-poor, α-rich stellar halos of massive galaxies. Together, these results describe a dense environment that has had a strong and continuing impact on the evolution of its low-mass neighbors.

scholarly journals Formation and Evolution of Nucleated Galaxies

2006 ◽  
Vol 2 (S235) ◽  
pp. 172-174
Author(s):  
Kenji Bekki
Keyword(s):  
Galaxy Formation ◽  
Globular Clusters ◽  
High Redshift ◽  
Galaxy Mergers ◽  
Galaxy Formation And Evolution ◽  
Central Regions ◽  
Low Mass ◽  
Formation And Evolution ◽  
Nuclear Structures ◽  
High Redshift Universe

AbstractWe discuss how stellar galactic nuclei (SGN) form and evolve during galaxy formation and evolution based on chemodynamical simulations on the central regions (1-1000 pc) of galaxies. Our simulations demonstrate that dissipative formation of SGN through rapid transfer of gas into the central 10 pc of galaxies is more consistent with recent observations of SGN than dissipationless formation of SGN through merging of globular clusters (GCs). Nuclear structures in the remnants of major galaxy mergers between low-mass, nucleated spirals are found to depend strongly on the mass-ratio of massive black holes (MBHs) to SGN in spirals in the sense that the remnants have more distinct SGN in the mergers with the smaller MBH-to-SGN-mass-ratios. During the destruction of low-mass, nucleated galaxies by strong tidal fields of giant galaxies, SGN can remain intact. The stripped SGN can be observed as bright GCs around the giant galaxies. The color-magnitude relation of metal-poor GCs (referred to as “the blue tilt”) recently discovered for bright galaxies is similar to that of SGN, which suggests that the origin of the blue tilt is closely associated with the formation processes of SGN of gas-rich, low-mass dwarfs in the high redshift universe.

scholarly journals New PARSEC database of alpha enhanced stellar evolutionary tracks and isochrones for Gaia

2015 ◽  
Vol 11 (A29B) ◽  
pp. 144-146
Author(s):  
Xiaoting Fu ◽  
Alessandro Bressan ◽  
Paola Marigo ◽  
Léo Girardi ◽  
Josefina Montalban ◽  
...  
Keyword(s):  
Stellar Evolution ◽  
Globular Clusters ◽  
Stellar Populations ◽  
Chemical Compositions ◽  
Early Type ◽  
Dwarf Stars ◽  
New Models ◽  
Multiple Population ◽  
Population Effects

AbstractWe present a new database of alpha enhanced evolutionary tracks and isochrones, computed with PARSEC (the PAdova & TRieste Stellar Evolution Code). The new isochrones are tested against Color-Magnitude Diagrams of well studied Globular Clusters, tacking into account multiple population effects. They are also compared with observations of dwarf stars in the Solar vicinity. After these preliminary computations, we will provide the full sets of isochrones with chemical compositions suitable for Globular Clusters and Bulge stars, that will be fully implemented into galaxy simulators. We will also provide new models suitable for the analysis of unresolved stellar populations in early type galaxies.

scholarly journals The extended Planetary Nebula Spectrograph (ePN.S) early-type galaxy survey: The kinematic diversity of stellar halos and the relation between halo transition scale and stellar mass

2018 ◽  
Vol 618 ◽  
pp. A94 ◽  
Author(s):  
C. Pulsoni ◽  
O. Gerhard ◽  
M. Arnaboldi ◽  
L. Coccato ◽  
A. Longobardi ◽  
...  
Keyword(s):  
Absorption Line ◽  
Phase Formation ◽  
Velocity Dispersion ◽  
Stellar Mass ◽  
Early Type ◽  
Two Phase ◽  
Low Surface Brightness ◽  
Central Regions ◽  
Adaptive Kernel ◽  
Kinematic Properties

Context. In the hierarchical two-phase formation scenario, the halos of early type galaxies (ETGs) are expected to have different physical properties from the galaxies’ central regions. Aims. The ePN.S survey characterizes the kinematic properties of ETG halos using planetary nebulae (PNe) as tracers, overcoming the limitations of absorption line spectroscopy at low surface brightness. Methods. We present two-dimensional velocity and velocity dispersion fields for 33 ETGs, including fast (FRs) and slow rotators (SRs). The velocity fields were reconstructed from the measured PN velocities using an adaptive kernel procedure validated with simulations, and extend to a median of 5.6 effective radii (Re). We complemented the PN kinematics with absorption line data from the literature, for a complete description of the kinematics from the center to the outskirts. Results. ETGs typically show a kinematic transition between inner regions and halo. Estimated transition radii in units of Re anti-correlate with stellar mass. SRs have increased but still modest rotational support at large radii. Most of the FRs show a decrease in rotation, due to the fading of the inner disk in the outer, more slowly rotating spheroid. 30% of the FRs are dominated by rotation also at large radii. Most ETGs have flat or slightly falling halo velocity dispersion profiles, but 15% of the sample have steeply falling profiles. All of the SRs and 40% of the FRs show signatures of triaxial halos such as kinematic twists or misalignments. We show with illustrative photometric models that this is consistent with the distribution of isophote twists from extended photometry. Conclusions. ETGs have more diverse kinematic properties in their halos than in the central regions. FRs do contain inner disk components but these frequently fade in outer spheroids which are often triaxial. The observed kinematic transition to the halo and its dependence on stellar mass is consistent with ΛCDM simulations and supports a two-phase formation scenario.

The X-ray binary populations of M81 and M82

2018 ◽  
Vol 14 (S346) ◽  
pp. 344-349
Author(s):  
Paul H. Sell ◽  
Andreas Zezas ◽  
Stephen J. Williams ◽  
Jeff J. Andrews ◽  
Kosmas Gazeas ◽  
...  
Keyword(s):  
Mass Transfer ◽  
Globular Clusters ◽  
Luminosity Function ◽  
Main Sequence ◽  
The Other ◽  
High Mass ◽  
Early Type ◽  
X Ray ◽  
Star Forming ◽  
Low Mass

AbstractWe use deep Chandra and HST data to uniquely classify the X-ray binary (XRB) populations in M81 on the basis of their donor stars and local stellar populations (into early-type main sequence, yellow giant, supergiant, low-mass, and globular cluster). First, we find that more massive, redder, and denser globular clusters are more likely to be associated with XRBs. Second, we find that the high-mass XRBs (HMXBs) overall have a steeper X-ray luminosity function (XLF) than the canonical star-forming galaxy XLF, though there is some evidence of variations in the slopes of the sub-populations. On the other hand, the XLF of the prototypical starburst M82 is described by the canonical powerlaw (αcum ∼ 0.6) down to LX ∼ 1036 erg s−1. We attribute variations in XLF slopes to different mass transfer modes (Roche-lobe overflow versus wind-fed systems).

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