2008A&A...491..113P

Query : 2008A&A...491..113P

2008A&A...491..113P - Astronomy and Astrophysics, volume 491, 113-129 (2008/11-3)

Extremely metal-poor star-forming galaxies. New detections and general morphological and photometric properties.

PAPADEROS P., GUSEVA N.G., IZOTOV Y.I. and FRICKE K.J.

Abstract (from CDS):

Extremely metal-deficient [12+log(O/H)≲7.6] emission-line galaxies in the nearby universe are invaluable laboratories of extragalactic astronomy and observational cosmology since they allow us to study collective star formation and the evolution of galaxies under chemical conditions approaching those in distant protogalactic systems. However, despite intensive searches over the last three decades, nearby star-forming (SF) galaxies with strongly subsolar metallicity remain extremely scarce. We searched the Sloan Digital Sky Survey (SDSS) and the Six-Degree Field Galaxy Redshift Survey (6dFGRS) for promising low-metallicity candidates using a variety of spectroscopic criteria. We present long-slit spectroscopy with the 3.6m ESO telescope of eight Hii regions in seven emission-line dwarf galaxies, selected from the Data Release 4 of SDSS (six galaxies) and from 6dFGRS (one galaxy). In addition, we use SDSS imaging data to investigate the photometric structure of the sample galaxies. From the 3.6m telescope spectra, we determine the oxygen abundance of these systems to be 7.3≲12+log(O/H)≲7.6, placing them among the most metal-poor star-forming galaxies ever discovered. Our photometric analysis reveals a moderately blue, stellar host galaxy in all sample galaxies. The detection of a stellar host in all galaxies studied here and all previously studied extremely metal-deficient SF galaxies implies that they are unlikely to be forming their first generation of stars. With regard to the structural properties of their host galaxy, we demonstrate that these systems are indistinguishable from blue compact dwarf (BCD) galaxies. However, in contrast to the majority (>90%) of BCDs that are characterised by red elliptical host galaxies, extremely metal-poor SF dwarfs (hereafter XBCDs) reveal moderately blue and irregular hosts. This is consistent with a young evolutionary status and in the framework of standard star formation histories implies that several XBCDs formed most of their stellar mass in the past ∼2Gyr. A large fraction of XBCDs reveal a cometary morphology due to the presence of intense SF activity at one edge of an elongated host galaxy with a gradually decreasing surface brightness towards its antipodal end.

Abstract Copyright: ∼

Journal keyword(s): galaxies: dwarf - galaxies: starburst - galaxies: abundances - galaxies: structure - galaxies: evolution

CDS comments: Fig. 9 J1044+353 is a misprint for J1044+0353, J1201+211 is a misprint for J1201+0211, J2302-0049 is a misprint for J2302+0049.

Simbad objects: 42

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Number of rows : 42
N Identifier Otype ICRS (J2000)
RA 		ICRS (J2000)
DEC 		Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2024 		#notes
1 NGC 185 Sy2 00 38 57.9400026024 +48 20 15.035874648   9.10 9.2     ~ 800 1
2 M 110 GiG 00 40 22.0572349992 +41 41 07.507220136   8.92 8.07     ~ 1308 1
3 UGC 772 LSB 01 13 40.450 +00 52 39.16   17       ~ 63 0
4 Mrk 996 Sy1 01 27 35.5248944352 -06 19 35.432857848 14.75 15.05 14.48 14.06 13.70 ~ 112 0
5 SDSS J013352.55+134209.5 EmG 01 33 52.555 +13 42 09.53           ~ 20 0
6 2dFGRS TGS380Z091 G 01 36 14.3 -29 42 43   18.401   18.342   ~ 2 0
7 SDSS J030149.01-005257.4 EmG 03 01 49.026 -00 52 57.39           ~ 11 0
8 2dFGRS TGS165Z225 G 03 13 02.5 -26 14 34   18.462   18.388   ~ 3 0
9 [PBT2001] SBSG 0335-052 W G 03 37 38.40 -05 02 37.5   19.14     18.85 ~ 107 1
10 [TIL97] 1 Cl* 03 37 44.0 -05 02 38           ~ 21 0
11 [TIL97] 7 Cl* 03 37 44.0 -05 02 38           ~ 9 0
12 [TIL97] 2 Cl* 03 37 44.0 -05 02 38           ~ 21 0
13 SBSG 0335-052B G 03 37 44.04 -05 02 40.2   16.77 16.65   16.79 ~ 185 1
14 6dFGS gJ040520.4-364859 EmG 04 05 20.4 -36 48 59           ~ 15 0
15 NGC 2537 AG? 08 13 14.643 +45 59 23.25 12.18 12.50 11.69 11.66   ~ 301 2
16 LEDA 2790884 bCG 08 25 55.5166210656 +35 32 31.833368556   18.2       ~ 120 1
17 UGC 4483 GiG 08 37 03.00 +69 46 31.0 15.70 15.46 14.98 14.89   ~ 302 0
18 US 1442 Sy1 08 40 29.9112912216 +47 07 10.241384412   18.2       ~ 62 0
19 SDSS J091159.43+313535.9 AG? 09 11 59.434 +31 35 35.92           ~ 14 0
20 Mrk 116 PaG 09 34 02.1 +55 14 25           ~ 1104 1
21 LEDA 27886 QSO 09 44 17.101 +54 11 28.83   19.5       ~ 71 0
22 UGC 5340 AG? 09 56 46.047 +28 49 43.77 14.82 14.74 14.59 14.55   ~ 227 1
23 NAME Sex A H2G 10 11 00.5 -04 41 30 12.48 12.13 11.93 11.78   ~ 727 2
24 [ITS2007] 52339-578-60 EmG 10 44 57.797 +03 53 13.15           ~ 48 0
25 MCG+10-17-011 AG? 11 32 02.6164558680 +57 22 36.292387908   17       ~ 59 1
26 LEDA 3120683 EmG 12 01 22.3051558008 +02 11 08.574134388           ~ 40 0
27 LEDA 39402 H2G 12 17 17.093 -28 02 32.67   17       ~ 135 0
28 ESO 380-27 H2G 12 25 46.95 -36 14 00.7   17.47   16.52   ~ 100 1
29 6dFGS gJ131742.7-010005 LSB 13 17 43.1868710184 -01 00 03.820032216   16.0   15.7 16.2 ~ 44 0
30 2QZ J132347.5-013252 EmG 13 23 47.4573498792 -01 32 52.048078188           ~ 40 0
31 LEDA 46982 bCG 13 25 48.66 -11 36 37.8           ~ 85 0
32 2dFGRS TGN206Z232 bCG 14 14 54.149 -02 08 22.92   18.065   17.598   ~ 23 0
33 MCG+07-29-060 QSO 14 17 01.716 +43 30 13.52   15.6       ~ 172 0
34 SDSS J210455.31-003522.3 G 21 04 55.310 -00 35 22.38           ~ 31 0
35 SDSS J213658.81+041404.0 bCG 21 36 58.82310 +04 14 04.0999           ~ 12 0
36 2dFGRS TGS062Z024 G 22 13 14.6 -24 15 48   18.087   17.955   ~ 2 0
37 2dFGRS TGS116Z004 G 22 13 26.1 -25 26 43   18.282   18.182   ~ 4 0
38 NAME Kinman Dwarf bCG 22 30 36.7959714600 -00 06 36.924915456 16.85 17.35 16.87   16.65 ~ 65 2
39 2dFGRS TGS258Z058 G 22 37 02.29 -28 52 43.7   19.218   19.141   ~ 4 0
40 HS 2236+1344 bCG 22 38 31.1192205216 +14 00 29.770282476           ~ 37 0
41 EQ J2302+0049 EmG 23 02 09.9920201040 +00 49 39.019513008           ~ 19 0
42 NAME Local Group GrG ~ ~           ~ 8385 0

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