Luminosity Functions for Globular Clusters

We present details of the database from a large Cycle 7 HST project to study the formation and evolution of rich star clusters in the LMC (see Elson et al., this volume). Our data set, which includes NICMOS, WFPC2 and STIS images of 8 clusters, will enable us to derive deep luminosity functions for the clusters and to investigate the universality of the stellar IMF. We will look for age spreads in the youngest clusters, quantify the population of binary stars in the cores of the clusters and at the half-mass radii, and follow the development of mass segregation.

Download Full-text

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

Proceedings of the International Astronomical Union ◽

10.1017/s1743921319007725 ◽

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.

Download Full-text

LUMINOSITY FUNCTIONS OF LMXBs IN CENTAURUS A: GLOBULAR CLUSTERS VERSUS THE FIELD

The Astrophysical Journal ◽

10.1088/0004-637x/701/1/471 ◽

2009 ◽

Vol 701 (1) ◽

pp. 471-480 ◽

Cited By ~ 34

Author(s):

Rasmus Voss ◽

Marat Gilfanov ◽

Gregory R. Sivakoff ◽

Ralph P. Kraft ◽

Andrés Jordán ◽

...

Keyword(s):

Globular Clusters ◽

Luminosity Functions ◽

Centaurus A

Download Full-text

Deep luminosity functions of globular clusters – IV. NGC 6171 ⋆

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/255.1.71 ◽

1992 ◽

Vol 255 (1) ◽

pp. 71-82 ◽

Cited By ~ 2

Author(s):

Francesco R. Ferraro ◽

Giampaolo Piotto

Keyword(s):

Globular Clusters ◽

Luminosity Functions

Download Full-text

Stellar parameters in the bulge cluster NGC 6553

Symposium - International Astronomical Union ◽

10.1017/s0074180900116699 ◽

1997 ◽

Vol 189 ◽

pp. 203-206 ◽

Cited By ~ 1

Author(s):

B. Barbuy ◽

S. Ortolani ◽

E. Bica ◽

A. Renzini ◽

M.D. Guarnieri

Keyword(s):

Globular Clusters ◽

Stellar Population ◽

Spectroscopic Analysis ◽

Galactic Center ◽

Stellar Populations ◽

The Sun ◽

Galactic Bulge ◽

Complete Understanding ◽

Luminosity Functions ◽

Bulge Formation

Globular clusters in the Galactic bulge form a flattened system, extending from the Galactic center to about 4.5 kpc from the Sun (Barbuy et al. 1997). A study of abundance ratios in these clusters is very important for a more complete understanding of the bulge formation. In this work we present a spectroscopic analysis of individual stars in NGC 6553. This cluster is a key one because it is located at d⊙ ≍ 5.1 kpc, therefore relatively close to us, and at the same time it is representative of the Galactic bulge stellar population: (a) Ortolani et al. (1995) showed that NGC 6553 and NGC 6528 show very similar Colour-Magnitude Diagrams (CMDs), and NGC 6528 is located at d⊙ ≍ 7.83 kpc, very close to the Galactic center; (b) the stellar populations of the Baade Window is also very similar to that of NGC 6553 and NGC 6528 as Ortolani et al. (1995) have shown by comparing their luminosity functions.

Download Full-text