J/ApJ/784/76 RR Lyrae variables in ESO294-G010 and ESO410-G005 (Yang+, 2014)
The early chemical enrichment histories of two Sculptor group dwarf galaxies as
revealed by RR Lyrae variables.
Yang S.-C., Wagner-Kaiser R., Sarajedini A., Kim S.C., Kyeong J.
<Astrophys. J., 784, 76 (2014)>
=2014ApJ...784...76Y 2014ApJ...784...76Y (SIMBAD/NED BibCode)
ADC_Keywords: Galaxies, nearby; Stars, variable ; Photometry, VRI ;
Stars, luminous
Keywords: galaxies: evolution - galaxies: formation - Local Group -
stars: variables: RR Lyrae
Abstract:
We present the results of our analysis of the RR Lyrae (RRL) variable
stars detected in two transition-type dwarf galaxies (dTrans),
ESO294-G010 and ESO410-G005 in the Sculptor group, which is known to
be one of the closest neighboring galaxy groups to our Local Group.
Using deep archival images from the Advanced Camera for Surveys on
board the Hubble Space Telescope, we have identified a sample of RRL
candidates in both dTrans galaxies (219 RRab (RR0) and 13 RRc (RR1)
variables in ESO294-G010; 225 RRab and 44 RRc stars in ESO410-G005).
The metallicities of the individual RRab stars are calculated via the
period-amplitude-[Fe/H] relation derived by Alcock et al. This yields
mean metallicities of <[Fe/H]>ESO294=-1.77±0.03 and
<[Fe/H]>ESO410=-1.64±0.03. The RRL metallicity distribution
functions (MDFs) are investigated further via simple chemical
evolution models; these reveal the relics of the early chemical
enrichment processes for these two dTrans galaxies. In the case of
both galaxies, the shapes of the RRL MDFs are well described by
pre-enrichment models. This suggests two possible channels for the
early chemical evolution for these Sculptor group dTrans galaxies: (1)
the ancient stellar populations of our target dwarf galaxies might
have formed from the star forming gas which was already enriched
through "prompt initial enrichment" or an "initial nucleosynthetic
spike" from the very first massive stars, or (2) this pre-enrichment
state might have been achieved by the end products from more evolved
systems of their nearest neighbor, NGC 55. We also study the
environmental effects of the formation and evolution of our target
dTrans galaxies by comparing their properties with those of 79 volume
limited (D☉<2Mpc) dwarf galaxy samples in terms of the
luminosity-metallicity relation and the H I gas content. The presence
of these RRL stars strongly supports the idea that although the
Sculptor Group galaxies have a considerably different environment from
the Local Group (e.g., no giant host galaxies, loosely bound and very
low local density), they share a common epoch of early star formation
with the dwarf satellite galaxies in the Local Group.
Description:
The science images of ESO294-G010 and ESO410-G005 used in this study
were taken with the Advanced Camera for Surveys Wide Field Channel
(ACS/WFC) on board Hubble Space Telescope (HST) as a part of GO-10503
(PI: Da Costa).
ESO294-G010 (R.A.=00:26:33.40 (J2000), Decl.=-41:51:19.0 (J2000)) was
observed on the HJD (+2453000) range 859.27358-861.13659 with the
F606W filter, and on the HJD (+2453000) range 859.40613-861.00342 with
the F814W filter. ESO410-G005 (R.A.=00:15:31.40 (J2000),
Decl.=-32:10:47.0 (J2000)) was observed on the HJD (+2453000) range
861.40425-863.21702 with the F606W filter, and on the HJD (+2453000)
range 861.53711-866.08158 with the filter F814W.
The central regions of each galaxy were placed on one of WFC chips so
that the imaging covers almost the entire visual extent of the
targets. ESO294-G010 was imaged 12 times in the F606W and 24 times in
the F814W filter with an exposure time of 1160s during the observing
baseline of ∼1.86days. The same number of exposures were obtained for
the observations of ESO410-G005 with an exposure time of 1120s over
the observing baseline of 4.55days.
The basic properties of each of these RRL candidates are summarized in
Tables 2 and 3.
We have also uncovered a significant number of Luminous Variable (LV)
candidates in both transition-type dwarf galaxies (22 in ESO294-G010;
19 in ESO410-G005). Their photometric and pulsation properties are
summarized in Table4.
File Summary:
--------------------------------------------------------------------------------
FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
table2.dat 69 232 Pulsation properties of RR Lyrae stars in
ESO294-G010
table3.dat 69 268 Pulsation properties of RR Lyrae stars in
ESO410-G005
table4.dat 76 38 Pulsation properties of anomalous Cepheids
table5.dat 95 79 Physical properties of nearby dwarf satellite
galaxies
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See also:
J/A+A/550/A7 : HST photometry of Sculptor dwarf galaxies (Lianou+, 2013)
J/AJ/145/101 : Updated nearby galaxy catalog (Karachentsev+, 2013)
J/MNRAS/425/1459 : RR Lyrae in M32 (Sarajedini+, 2012)
J/AJ/141/171 : RR Lyrae in six ultra-deep fields of M31 (Jeffery+, 2011)
J/AJ/139/357 : Variable stars in NGC 5286 (Zorotovic+, 2010)
J/ApJ/724/799 : RR Lyrae variables in M33. II. (Yang+, 2010)
J/AJ/132/1361 : RR Lyrae variables in M33 (Sarajedini+, 2006)
J/AJ/129/267 : RR Lyrae variables in NGC 5272 (Cacciari+, 2005)
J/AJ/127/2031 : Catalog of neighboring galaxies (Karachentsev+, 2004)
Byte-by-byte Description of file: table[23].dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 4 A4 --- Type RR Lyrae type (RRab or RRc)
6- 9 A4 --- Field HST/ACS field (WFC1 or WFC2) (G1)
11- 15 I5 --- Star [14904/36753] Variable identifier
17 I1 h RAh Hour of Right Ascension (J2000)
19- 20 I2 min RAm Minute of Right Ascension (J2000)
22- 26 F5.2 s RAs Second of Right Ascension (J2000)
28 A1 --- DE- Sign of the Declination (J2000)
29- 30 I2 deg DEd Degree of Declination (J2000)
32- 33 I2 arcmin DEm Arcminute of Declination (J2000)
35- 39 F5.2 arcsec DEs Arcsecond of Declination (J2000)
41- 46 F6.3 mag <Vmag> [26.6/27.3] Mean Johnson V band magnitude
(VEGAmag system)
48- 52 F5.3 mag <V-I> [0.17/0.73] Mean Johnson (V-I) color index
(VEGAmag system)
54- 59 F6.4 d Per [0.2/0.83] Period
61- 66 F6.4 mag Vamp [0.32/1.5] V band amplitude
68- 69 A2 --- Bl [bl] The flag "bl" indicates a blended object
--------------------------------------------------------------------------------
Byte-by-byte Description of file: table4.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 11 A11 --- Galaxy Galaxy identifier (ESO294-G010 or ESO410-G005)
13- 16 A4 --- Field HST/ACS field (WFC1 or WFC2) (G1)
18- 22 I5 --- Star [879/23638] Variable identifier
24 I1 h RAh Hour of Right Ascension (J2000)
26- 27 I2 min RAm Minute of Right Ascension (J2000)
29- 33 F5.2 s RAs Second of Right Ascension (J2000)
35 A1 --- DE- Sign of the Declination (J2000)
36- 37 I2 deg DEd Degree of Declination (J2000)
39- 40 I2 arcmin DEm Arcminute of Declination (J2000)
42- 46 F5.2 arcsec DEs Arcsecond of Declination (J2000)
48- 53 F6.3 mag <Vmag> [24.2/26.6] Mean Johnson V band magnitude
(VEGAmag system)
55- 59 F5.3 mag <V-I> [0.25/0.7] Mean Johnson (V-I) color index
(VEGAmag system)
61- 66 F6.4 d Per [0.42/1.95] Period
68- 73 F6.4 mag Vamp [0.25/1.29] The V band amplitude
75- 76 A2 --- Bl [bl] The flag "bl" indicates a blended object
--------------------------------------------------------------------------------
Byte-by-byte Description of file: table5.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 8 A8 --- Group Galaxy group (MW, M31, Antilia, or Sculptor)
10- 20 A11 --- Name Name of the nearby dwarf satellite galaxy (1)
22- 23 I2 h RAh Hour of Right Ascension (J2000)
25- 26 I2 min RAm Minute of Right Ascension (J2000)
28- 31 F4.1 s RAs Second of Right Ascension (J2000)
33 A1 --- DE- Sign of the Declination (J2000)
34- 35 I2 deg DEd Degree of Declination (J2000)
37- 38 I2 arcmin DEm Arcminute of Declination (J2000)
40- 41 I2 arcsec DEs Arcsecond of Declination (J2000)
43- 46 F4.2 Mpc Dist [0.02/1.97]Distance from the Sun (D☉)
48- 52 F5.1 mag BMag [-17.9/-0.7]? Absolute B band magnitude
54- 58 F5.2 [Sun] <[Fe/H]> [-2.7/-0.5]? Mean metallicity
60- 63 F4.2 [Sun] e_<[Fe/H]> [0.03/0.8]? Uncertainty in <[Fe/H]>
65- 74 A10 --- r_<[Fe/H]> Reference for <[Fe/H]> (2)
76- 79 F4.2 [Msun] logMHI [1.12/8.66]? Log of HI mass
81- 84 F4.2 [Lsun] logLK [3.24/9.42]? Log of K-band luminosity
86- 89 F4.1 --- Ti5 [-0.7/5.3] The tidal index (Θ5) (3)
91- 95 A5 --- MType Galaxy morphological type (BCD, dE, dIrr,
dSph, dTran, or uFd) (4)
--------------------------------------------------------------------------------
Note (1): Our compilation includes the recently discovered ultra-faint dwarf
systems (uFds) around the Milky Way, and faint Andromeda dwarf galaxies
(Willman et al., 2005AJ....129.2692W 2005AJ....129.2692W, 2005ApJ...626L..85W 2005ApJ...626L..85W; Belokurov et
al., 2006ApJ...647L.111B 2006ApJ...647L.111B; Zucker et al., 2004ApJ...612L.121Z 2004ApJ...612L.121Z,
2006ApJ...643L.103Z 2006ApJ...643L.103Z, 2006ApJ...650L..41Z 2006ApJ...650L..41Z, 2007ApJ...659L..21Z 2007ApJ...659L..21Z; Irwin et
al., 2007ApJ...656L..13I 2007ApJ...656L..13I, 2008ApJ...676L..17I 2008ApJ...676L..17I; Walsh et al.,
2007ApJ...662L..83W 2007ApJ...662L..83W; McConnachie et al., 2008ApJ...688.1009M 2008ApJ...688.1009M; Martin et
al., 2009ApJ...705..758M 2009ApJ...705..758M; Richardson et al., 2011ApJ...732...76R 2011ApJ...732...76R; Bell et
al., 2011ApJ...742L..15B 2011ApJ...742L..15B; Slater et al., 2011ApJ...742L..14S 2011ApJ...742L..14S).
Note (2): Reference for the quoted metallicity value is defined as follows:
1 = Grebel et al. (2003AJ....125.1926G 2003AJ....125.1926G);
2 = Norris et al. 2010 (cat. J/ApJ/723/1632);
3 = Yang & Sarajedini (2012MNRAS.419.1362Y 2012MNRAS.419.1362Y);
4 = Kirby et al. (2008ApJ...685L..43K 2008ApJ...685L..43K);
5 = Willman et al. (2011AJ....142..128W 2011AJ....142..128W).
Note (3): The Θ5 is a measure of tidal force strength on a given galaxy
exerted by the five most influential neighbors. The high positive
Θ5 values indicate a galaxy residing in a dense environment, and
the negative values of Θ5 represent isolated galaxies or galaxies
in a very low density environment. The majority of gas-rich dIrr galaxies
tend to have lower tidal indices except for the LMC/SMC pair, while
dSph/uFd/dE galaxies have predominantly high positive values (i.e., there
are no early-type dwarf satellites having a Θ5 value less than 1).
Note (4): Morphology of galaxy defined as follows:
dSph = dwarf spheroidal galaxy;
dTran = transition-type dwarf galaxy;
uFd = ultra-faint dwarf system.
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Global Notes:
Note (G1): HST/ACS=Advanced Camera for Surveys Wide Field Channel (ACS/WFC) on
board Hubble Space Telescope (HST).
History:
From electronic version of the journal
(End) Prepared by [AAS]; Sylvain Guehenneux [CDS] 08-Aug-2016