2007A&A...468..973M

Query : 2007A&A...468..973M

2007A&A...468..973M - Astronomy and Astrophysics, volume 468973-978 (2007/6-4)

The blue plume population in dwarf spheroidal galaxies. Genuine blue stragglers or young stellar population?

MOMANY Y., HELD E.V., SAVIANE I., ZAGGIA S., RIZZI L. and GULLIEUSZIK M.

Abstract (from CDS):

Blue stragglers (BSS) in the Milky Way field and globular/open clusters are thought to be the product of either primordial or collisional binary systems. In the context of dwarf spheroidal galaxies it is hard to firmly disentangle a genuine BSS population from young main sequence (MS) stars tracing a ∼1-2Gyr old star forming episode. Assuming that their blue plume populations are made of BSS, we estimate the BSS frequency (FBSSHB; as normalized to the horizontal branch star counts) for 8 Local Group non star-forming dwarf galaxies, using a compilation of ground and space based photometry. (i) The BSS frequency in dwarf galaxies, at any given MV, is always higher than that in globular clusters of similar luminosities; (ii) the BSS frequency for the lowest luminosity dwarf galaxies is in excellent agreement with that observed in the Milky Way halo and open clusters; and most interestingly (iii) derive a statistically significant FBSSHB-MV anti-correlation for dwarf galaxies, similar to that observed in globular clusters. The low density, almost collision-less, environments of our dwarf galaxy sample allow us to infer (i) their very low dynamical evolution; (ii) a negligible production of collisional BSS; and consequently (iii) that their blue plumes are mainly made of primordial binaries. The dwarf galaxies FBSSHB-MV anti-correlation can be used as a discriminator: galaxies obeying the anti-correlation are more likely to possess genuine primordial BSS rather than young main sequence stars.

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Journal keyword(s): stars: galaxies: dwarf - blue stragglers - galaxies: stellar content - stars: Hertzspring-Russell (HR) and C-M diagrams - galaxies: Local Group - galaxies: photometry

Simbad objects: 26

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Number of rows : 26
N Identifier Otype ICRS (J2000)
RA 		ICRS (J2000)
DEC 		Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2026 		#notes
1 NAME Andromeda I G 00 45 39.8 +38 02 28   13.9 12.7     ~ 355 0
2 NAME Sculptor Dwarf Galaxy G 01 00 09.4 -33 42 32   9.79 8.6 8.81   ~ 1498 4
3 NAME Andromeda II G 01 16 29.8 +33 25 09     11.7     ~ 402 0
4 NGC 1841 GlC 04 45 24.38 -83 59 53.3   12.23 11.43     ~ 190 0
5 NAME LMC Bar PoG 05 22 08 -69 23.5           ~ 343 0
6 NAME LMC G 05 23 34.6 -69 45 22     0.4     ~ 19090 0
7 ESO 206-20A G 06 41 36.7 -50 57 58   22.14 11.0 19.47   ~ 1190 0
8 NGC 2419 GlC 07 38 08.51 +38 52 54.9     10.05     ~ 998 0
9 NAME Sextans dSph LSB 10 13 02.9 -01 36 53   12 10.4     ~ 921 0
10 NAME UMa I Galaxy G 10 34 52.80 +51 55 12.0     14.4     ~ 355 1
11 NAME Willman 1 G 10 49 21.0 +51 03 00     15.2     ~ 345 0
12 Z 126-111 G 11 13 28.13 +22 09 10.1   12.9 12.0     ~ 899 0
13 NAME Leo IV LSB 11 32 57.0 -00 32 00     15.1     ~ 419 1
14 NGC 5139 GlC 13 26 47.28 -47 28 46.1           ~ 3677 0
15 NAME Bootes Dwarf Spheroidal Galaxy G 14 00 00.0 +14 30 00     12.8     ~ 491 0
16 Z 318-18 G 15 09 08.0 +67 13 21   13.60 10.6     ~ 1459 0
17 NGC 5946 GlC 15 35 28.58 -50 39 35.0           ~ 210 0
18 M 80 GlC 16 17 02.41 -22 58 33.9           ~ 780 0
19 Z 300-12 G 17 20 14.335 +57 55 16.39   12.40 10.6     ~ 1428 1
20 NAME Galactic Center reg 17 45 39.60213 -29 00 22.0000           ~ 16269 0
21 M 54 GlC 18 55 03.33 -30 28 47.5           ~ 1164 0
22 NGC 6717 GlC 18 55 06.04 -22 42 05.3           ~ 273 0
23 NAME SDG G 18 55 19.0 -30 32 43   4.5 3.6     ~ 2438 2
24 M 71 GlC 19 53 46.49 +18 46 45.1           ~ 1190 0
25 M 2 GlC 21 33 27.02 -00 49 23.7     6.25     ~ 1114 1
26 NAME Local Group GrG ~ ~           ~ 9325 0

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