2007PASP..119..939G


C.D.S. - SIMBAD4 rel 1.7 - 2021.03.05CET23:39:55

2007PASP..119..939G - Publ. Astron. Soc. Pac., 119, 939-961 (2007/September-0)

Chemical abundances and kinematics in globular clusters and local group dwarf galaxies and their implications for formation theories of the galactic halo.

GEISLER D., WALLERSTEIN G., SMITH V.V. and CASETTI-DINESCU D.I.

Abstract (from CDS):

We review Galactic halo formation theories and supporting evidence, in particular, kinematics and detailed chemical abundances of stars in some relevant globular clusters as well as Local Group dwarf galaxies. Outer halo red HB clusters tend to have large eccentricities and inhabit the area of the Lee diagram populated by dwarf spheroidal stars, favoring an extragalactic origin. Old globular clusters show the full range of eccentricities, while younger ones seem to have preferentially high eccentricities, again hinting at their extragalactic origin. However, the three outer halo second parameter clusters with well-determined orbits indicate they come from three independent systems. We compare detailed abundances of a variety of elements between the halo and all dwarf galaxies studied to date, including both dwarf spheroidals and irregulars. The salient feature is that halo abundances are essentially unique. In particular, the general α vs. [Fe/H] pattern of 12 of the 13 galaxies studied are similar to each other and very different from the Milky Way. Sgr appears to be the only possible exception. At the metal-poor end the extragalactic sample is only slightly deficient compared to the halo but begins to diverge by [Fe/H] ∼ -2 and the difference is particularly striking for stars with [Fe/H] ∼ -1. Only Sgr, the most massive dSph, has some stars similar in α-abundance to Galactic stars at intermediate metallicities, even the most extreme low-α subset most likely to have been accreted. It appears very unlikely that a significant fraction of the metal-rich halo could have come from disrupted dSphs of low mass. However, at least some of the metal-poor halo may have come from typical dSphs, and a portion of the intermediate metallicity and metal-rich halo may have come from very massive systems like Sgr. This argues against the standard hierarchical galaxy formation scenario and the Searle-Zinn paradigm for the formation of the Galactic halo via accretion of ``fragments'' composed of stars like those we see in typical present-day dSphs. The chemical differences between the dwarfs and the halo are due to a combination of a low star formation efficiency and a high galactic wind efficiency in the former. AGB stars are also more important in the chemical evolution of the dwarfs. The formation problem may be solved if the majority of halo stars formed within a few, very massive satellites accreted very early. However, any such satellites must either be accreted much earlier than postulated, before the onset of SNe Ia, or star formation must be prevented to occur in them until only shortly before they are accreted. The intrinsic scatter in many elements, particularly the α-elements, indicates that the halo was also mixed on a surprisingly short timescale, a further problem for hierarchical formation theories.

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Journal keyword(s): Reviews

Simbad objects: 35

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Number of rows : 35

N Identifier Otype ICRS (J2000)
RA
ICRS (J2000)
DEC
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2021
#notes
1 NAME WLM Galaxy G 00 01 57.9 -15 27 50   11.50 11.10 10.93   ~ 590 2
2 NGC 104 GlC 00 24 05.359 -72 04 53.20   5.78 4.09     ~ 3619 0
3 M 31 G 00 42 44.330 +41 16 07.50 4.86 4.36 3.44     ~ 11217 1
4 NAME SMC G 00 52 38.0 -72 48 01   2.79 2.2     ~ 9710 1
5 NAME Scl Group GrG 01 00 06 -33 44.2           ~ 467 0
6 IC 1613 GiC 01 04 54.2 +02 08 00   10.42 10.01 9.77   ~ 1122 2
7 Cl Pal 1 GlC 03 33 20.04 +79 34 51.8   17.2       ~ 206 1
8 NAME E 1 GlC 03 55 02.5 -49 36 52           ~ 183 0
9 NAME CL ERID 1 GlC 04 24 44.5 -21 11 13           ~ 161 1
10 NAME LMC G 05 23 34.6 -69 45 22     0.4     ~ 15214 1
11 NGC 2419 GlC 07 38 08.51 +38 52 54.9     10.05     ~ 831 0
12 BD+80 245 Pe* 08 11 06.2395845271 +79 54 29.558601814   10.50 9.96 9.88   G0 101 0
13 NAME Sextans C GlC 10 05 30.96 +00 04 15.4   15.5 13.9     ~ 296 1
14 NAME Sex A H2G 10 11 00.5 -04 41 30 12.48 12.13 11.93 11.78   ~ 662 2
15 NGC 3201 GlC 10 17 36.82 -46 24 44.9   9.18 8.24     ~ 749 0
16 NAME Leo B G 11 13 28.13 +22 09 10.1   12.9 12.0     ~ 754 0
17 GCl 17 GlC 11 29 16.80 +28 58 25.0   14.4       ~ 322 1
18 C 1235-509 GlC 12 38 40.20 -51 09 01.0           ~ 327 0
19 NGC 5139 GlC 13 26 47.28 -47 28 46.1   6.12 5.33     ~ 3075 0
20 M 3 GlC 13 42 11.62 +28 22 38.2     6.39     ~ 2298 0
21 NGC 5466 GlC 14 05 27.29 +28 32 04.0   10.5 9.70     ~ 742 0
22 NAME Serpens Dwarf GlC 15 16 05.30 -00 06 41.0   15.1       ~ 641 1
23 GCl 38 GlC 16 10 59.00 +14 57 42.0           ~ 333 0
24 M 13 GlC 16 41 41.634 +36 27 40.75     5.8     ~ 2036 0
25 NAME SDG G 18 55 03.1 -30 28 42   4.5 3.6     ~ 1814 2
26 M 54 GlC 18 55 03.33 -30 28 47.5           ~ 933 0
27 Cl Terzan 7 GlC 19 17 43.92 -34 39 27.8           ~ 371 0
28 Cl Arp 2 GlC 19 28 44.11 -30 21 20.3     12.41     ~ 308 0
29 Cl Terzan 8 GlC 19 41 44.41 -33 59 58.1     11.54     ~ 266 0
30 NGC 6822 G 19 44 56.199 -14 47 51.29   18 8.1     ~ 1453 0
31 M 71 GlC 19 53 46.49 +18 46 45.1   7.91 6.1     ~ 1038 0
32 NGC 7006 GlC 21 01 29.465 +16 11 16.49     10.46     ~ 490 0
33 Cl Pal 12 GlC 21 46 38.84 -21 15 09.4     11.89     ~ 459 0
34 GCl 124 GlC 23 06 44.48 +12 46 19.2   15.6       ~ 239 1
35 NGC 7492 GlC 23 08 26.68 -15 36 41.3     10.48     ~ 264 0

    Equat.    Gal    SGal    Ecl

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2021.03.05-23:39:55

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