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

Full paper

View the references in ADS

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 - 2023	#notes
1	NGC 185	Sy2	00 38 57.9400026024	+48 20 15.035874648		9.10	9.2			~	782	1
2	M 110	GiG	00 40 22.0572349992	+41 41 07.507220136		8.92	8.07			~	1280	1
3	UGC 772	LSB	01 13 40.450	+00 52 39.16		17				~	61	0
4	QSO B0125-0635	QSO	01 27 35.5248944352	-06 19 35.432857848	14.75	15.05	14.48	14.06	13.70	~	100	0
5	SDSS J013352.55+134209.5	EmG	01 33 52.555	+13 42 09.53						~	19	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						~	10	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	~	172	1
14	6dFGS gJ040520.4-364859	G	04 05 20.4	-36 48 59						~	11	0
15	NGC 2537	IG	08 13 14.643	+45 59 23.25	12.18	12.50	11.69	11.66		G0V	291	1
16	LEDA 2790884	bCG	08 25 55.5166210656	+35 32 31.833368556		18.2				~	112	1
17	UGC 4483	GiG	08 37 03.29	+69 46 29.2	15.70	15.46	14.98	14.89		~	289	0
18	LEDA 24384	Sy1	08 40 29.9112912216	+47 07 10.241384412		18.2				~	60	0
19	SDSS J091159.43+313535.9	G	09 11 59.434	+31 35 35.92						~	11	0
20	Mrk 116	PaG	09 34 02.1	+55 14 25						~	1080	1
21	LEDA 27886	QSO	09 44 17.101	+54 11 28.83		19.5				~	68	0
22	UGC 5340	G	09 56 46.047	+28 49 43.77	14.82	14.74	14.59	14.55		~	210	1
23	NAME Sex A	H2G	10 11 00.5	-04 41 30	12.48	12.13	11.93	11.78		~	714	2
24	[ITS2007] 52339-578-60	EmG	10 44 57.797	+03 53 13.15						~	40	0
25	MCG+10-17-011	G	11 32 02.6164558680	+57 22 36.292387908		17				~	53	1
26	LEDA 3120683	EmG	12 01 22.3051558008	+02 11 08.574134388						~	35	0
27	LEDA 39402	H2G	12 17 17.093	-28 02 32.67		17				~	134	0
28	ESO 380-27	H2G	12 25 46.9	-36 14 01		17.47		16.52		~	99	1
29	6dFGS gJ131742.7-010005	LSB	13 17 43.1868710184	-01 00 03.820032216		16.0		15.7	16.2	~	42	0
30	2QZ J132347.5-013252	EmG	13 23 47.4573498792	-01 32 52.048078188						~	36	0
31	LEDA 46982	bCG	13 25 48.60	-11 36 38.0						~	82	0
32	2dFGRS TGN206Z232	bCG	14 14 54.149	-02 08 22.92		18.065		17.598		~	22	0
33	MCG+07-29-060	QSO	14 17 01.716	+43 30 13.52		15.6				~	165	0
34	SDSS J210455.31-003522.3	G	21 04 55.310	-00 35 22.38						~	29	0
35	HS 2134+0400	bCG	21 36 58.95	+04 14 04.1						~	11	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	~	64	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						~	35	0
41	EQ J2302+0049	EmG	23 02 09.9920201040	+00 49 39.019513008						~	17	0
42	NAME Local Group	GrG	~	~						~	8040	0

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