Dwarf Spheroidal Galaxies and Globular Clusters

Recent observational results for dwarf spheroidal galaxies are reviewed and discussed. In particular, the differences in stellar populations between dwarf spheroidal galaxies and globular clusters are highlighted. It seems most probable that the origin and evolution of dwarf spheroidal galaxies was very different from that of globular clusters.

Population gradients in dwarf spheroidal galaxies KKs 3 and ESO 269-66

Proceedings of the International Astronomical Union ◽

10.1017/s1743921318005550 ◽

2018 ◽

Vol 14 (S344) ◽

pp. 420-421

Author(s):

M. E. Sharina ◽

L. N. Makarova ◽

D. I. Makarov

Keyword(s):

Surface Density ◽

Globular Clusters ◽

Stellar Populations ◽

Density Profiles ◽

Star Forming ◽

Central Regions ◽

Low Metallicity ◽

High Metallicity ◽

AbstractWe compare the properties of stellar populations for globular clusters (GCs) and field stars in two dwarf spheroidal galaxies (dSphs): ESO269-66, a close neighbour of NGC5128, and KKs3, one of the few isolated dSphs within 10 Mpc. We analyse the surface density profiles of low and high metallicity (blue and red) stars in two galaxies using the Sersic law. We argue that 1) the density profiles of red stars are steeper than those of blue stars, which evidences in favour of the metallicity and age gradients in dSphs; 2) globular clusters in KKs3 and ESO 269-66 contain 4 and 40 percent of all stars with [Fe / H] ~ 1.6 dex and the age of 12 Gyr, correspondingly. Therefore, GCs are relics of the first powerful star-forming bursts in the central regions of the galaxies. KKs 3 has lost a smaller percentage of old low-metallicity stars than ESO269-66, probably, thanks to its isolation.

Globular clusters and dwarf spheroidal galaxies of the outer galactic halo: On the putative scenario of their formation

Astronomical and Astrophysical Transactions ◽

10.1080/10556790108208191 ◽

2001 ◽

Vol 20 (1) ◽

pp. 89-92

Author(s):

V. V. Kravtsov

Keyword(s):

Globular Clusters ◽

Galactic Halo ◽

Variable Stars in Dwarf Spheroidal Galaxies

International Astronomical Union Colloquium ◽

10.1017/s0252921100033315 ◽

1973 ◽

Vol 21 ◽

pp. 35-48

Author(s):

Steven Van Agt

Keyword(s):

Globular Clusters ◽

Local Group ◽

Elliptical Galaxies ◽

Variable Stars ◽

Theoretical Predictions ◽

History Of ◽

Set Up ◽

Theoretical Considerations ◽

Interest in dwarf spheroidal galaxies is motivated by a number of reasons; an important one on the occasion of this colloquium is the abundance of variable stars. The theory of stellar evolution and stellar pulsations is now able to predict from theoretical considerations characteristic properties of variable stars in the colour-magnitude diagram (Iben, 1971). By observing the variable stars in the field, and in as wide a selection of objects as possible, more insight can be obtained into the history of the oldest members of our Galaxy (the globular clusters) and of the dwarf spheroidal galaxies in the Local Group. It is worthwhile to explore the spheroidal galaxies as observational tests for the theoretical predictions of conditions in space away from our Galaxy. The numbers of variable stars in the dwarf spheroidal galaxies are such that we may expect well-defined relations to emerge once reliable magnitude sequences have been set up, the variable stars found, and their periods determined. Six dwarf spheroidal galaxies are presently known in the Local Group within a distance of 250 kpc. In Table I, which lists members of the Local Group, they are at the low-luminosity end of the sequence of elliptical galaxies (van den Bergh, 1968).

A near-infrared view of AGB stars in nearby dwarf galaxies

Proceedings of the International Astronomical Union ◽

10.1017/s1743921310003169 ◽

2009 ◽

Vol 5 (S262) ◽

pp. 345-346

Author(s):

M. Gullieuszik ◽

E. V. Held ◽

L. Girardi ◽

L. Rizzi ◽

P. Marigo ◽

...

Keyword(s):

Near Infrared ◽

Dwarf Galaxies ◽

Theoretical Models ◽

Stellar Populations ◽

Agb Stars ◽

Luminosity Functions ◽

AbstractAs part of our near-infrared photometric survey of nearby dwarf galaxies, we present recent results for Leo I and Leo II dwarf spheroidal galaxies. We selected O- and C-rich AGB stellar populations using two-color diagrams and compared their luminosity functions and star counts with the predictions of the most recent AGB theoretical models.

Conference Summary

Proceedings of the International Astronomical Union ◽

10.1017/s1743921312009714 ◽

2011 ◽

Vol 7 (S284) ◽

pp. 500-507

Author(s):

Jay Gallagher ◽

Carol Lonsdale ◽

Gustavo Bruzual

Keyword(s):

Interstellar Medium ◽

Type Systems ◽

Stellar Populations ◽

Early Type ◽

Complete Understanding ◽

Conference Summary ◽

Relativistic Particles ◽

If galaxies consisted only of stars, and some early-type systems in general and dwarf spheroidal galaxies in particular fit this prescription, then the calculation of the SED in principle is straightforward. The emergent luminosity at any wavelength simply is the sum over all the luminosities of all the stars in the system. This can be calculated, of course provided that one has a complete understanding of stellar populations, which remains a non-trivial issue. Most galaxies, however, also contain an interstellar medium (ISM). The ISM absorbs, scatters and reprocesses the radiation and relativistic particles from sources within galaxies, primarily stars and AGN. That the ISM is neither isotropic nor homogeneous adds to the challenge of how to properly account for its influence on the luminosity emerging from galaxies.