2021ApJ...908...18S


C.D.S. - SIMBAD4 rel 1.7 - 2021.05.17CEST21:51:52

2021ApJ...908...18S - Astrophys. J., 908, 18-18 (2021/February-2)

Eridanus II: a fossil from reionization with an off-center star cluster.

SIMON J.D., BROWN T.M., DRLICA-WAGNER A., LI T.S., AVILA R.J., BECHTOL K., CLEMENTINI G., CRNOJEVIC D., GAROFALO A., GEHA M., SAND D.J., STRADER J. and WILLMAN B.

Abstract (from CDS):

We present deep Hubble Space Telescope (HST) photometry of the ultra-faint dwarf galaxy Eridanus II (Eri II). Eri II, which has an absolute magnitude of MV = -7.1, is located at a distance of 339 kpc, just beyond the virial radius of the Milky Way. We determine the star formation history of Eri II and measure the structure of the galaxy and its star cluster. We find that a star formation history consisting of two bursts, constrained to match the spectroscopic metallicity distribution of the galaxy, accurately describes the Eri II stellar population. The best-fit model implies a rapid truncation of star formation at early times, with >80% of the stellar mass in place before z ∼ 6. A small fraction of the stars could be as young as 8 Gyr, but this population is not statistically significant; Monte Carlo simulations recover a component younger than 9 Gyr only 15% of the time, where they represent an average of 7 ± 4% of the population. These results are consistent with theoretical expectations for quenching by reionization. The HST depth and angular resolution enable us to show that Eri II's cluster is offset from the center of the galaxy by a projected distance of 23 ± 3 pc. This offset could be an indication of a small (∼50-75 pc) dark matter core in Eri II. Moreover, we demonstrate that the cluster has a high ellipticity of 0.31–0.06+0.05 and is aligned with the orientation of Eri II within 3° ± 6°, likely due to tides. The stellar population of the cluster is indistinguishable from that of Eri II itself.

Abstract Copyright: © 2021. The American Astronomical Society. All rights reserved.

Journal keyword(s): Dwarf galaxies - Local Group - Globular star clusters - Stellar populations - Galaxy ages - Dark matter - Galaxy structure

Status at CDS : Examining the need for a new acronym. // Large table(s) will be appraised for possible ingestion in VizieR.

Simbad objects: 25

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Number of rows : 25

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 Andromeda XXV G 00 30 08.9 +46 51 07     14.8     ~ 94 0
2 M 31 G 00 42 44.330 +41 16 07.50 4.86 4.36 3.44     ~ 11311 1
3 NAME Tri II G 02 13 17.40 +36 10 42.4           ~ 80 0
4 NAME Sgr Stream St* 02 22 +00.0           ~ 697 0
5 NAME Fornax Dwarf Spheroidal G 02 39 59.3 -34 26 57   9.02 7.4     ~ 1534 1
6 NAME Cluster 6 in Fornax Cl* 02 40 06.90 -34 25 19.2           ~ 10 0
7 NAME Magellanic Clouds GrG 03 00 -71.0           ~ 5935 1
8 Gaia DR2 4836638439545141504 * 03 44 15.6174757833 -43 32 30.290645168           ~ 1 0
9 NAME Eridanus II G 03 44 21.1 -43 32 00           ~ 109 0
10 NAME Eridanus II Cluster Cl* 03 44 22.20 -43 31 59.2           ~ 3 0
11 NAME LMC G 05 23 34.6 -69 45 22     0.4     ~ 15357 1
12 Koposov 2 GlC 07 58 17.00 +26 15 19.4           ~ 60 1
13 NAME Leo T dSph G 09 34 53.4 +17 03 05     15.1     ~ 322 0
14 NAME Crater Cluster GlC 11 36 16.20 -10 52 38.8           ~ 66 1
15 MCS J1149.5+2223 ClG 11 49 35.8 +22 23 55           ~ 350 0
16 Koposov 1 GlC 11 59 18.40 +12 15 35.8           ~ 59 0
17 C 1353-269 GlC 13 56 21.702 -27 10 03.00           ~ 109 0
18 NAME Munoz 1 Cl* 15 01 48.02 +66 58 07.3           ~ 16 0
19 NAME Draco II Gl? 15 52 47.6 +64 33 55           ~ 64 0
20 M 19 GlC 17 02 37.69 -26 16 04.6   8.45 5.57     ~ 323 1
21 M 92 GlC 17 17 07.39 +43 08 09.4     6.52     ~ 1943 0
22 Cl Pal 12 GlC 21 46 38.84 -21 15 09.4     11.89     ~ 465 0
23 NAME Balbinot 1 Cl* 22 10 42.819 +14 56 49.03           ~ 23 0
24 NAME Kim 1 Cl* 22 11 41.30 +07 01 31.8           ~ 24 0
25 NAME Local Group GrG ~ ~           ~ 7264 0

    Equat.    Gal    SGal    Ecl

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2021.05.17-21:51:52

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