2011ApJ...743...77M

Query : 2011ApJ...743...77M

2011ApJ...743...77M - Astrophys. J., 743, 77 (2011/December-2)

Systematic search for extremely metal-poor galaxies in the Sloan Digital Sky Survey.

MORALES-LUIS A.B., SANCHEZ ALMEIDA J., AGUERRI J.A.L. and MUNOZ-TUNON C.

Abstract (from CDS):

We carry out a systematic search for extremely metal-poor (XMP) galaxies in the spectroscopic sample of Sloan Digital Sky Survey (SDSS) data release 7 (DR7). The XMP candidates are found by classifying all the galaxies according to the form of their spectra in a region 80 Å wide around Hα. Due to the data size, the method requires an automatic classification algorithm. We use k-means. Our systematic search renders 32 galaxies having negligible [N II] lines, as expected in XMP galaxy spectra. Twenty-one of them have been previously identified as XMP galaxies in the literature–the remaining 11 are new. This was established after a thorough bibliographic search that yielded only some 130 galaxies known to have an oxygen metallicity 10 times smaller than the Sun (explicitly, with 12 + log (O/H) ≤ 7.65). XMP galaxies are rare; they represent 0.01% of the galaxies with emission lines in SDSS/DR7. Although the final metallicity estimate of all candidates remains pending, strong-line empirical calibrations indicate a metallicity about one-tenth solar, with the oxygen metallicity of the 21 known targets being 12 + log (O/H) ≃ 7.61±0.19. Since the SDSS catalog is limited in apparent magnitude, we have been able to estimate the volume number density of XMP galaxies in the local universe, which turns out to be (1.32±0.23)x10–4/Mpc3. The XMP galaxies constitute 0.1% of the galaxies in the local volume, or ∼0.2% considering only emission-line galaxies. All but four of our candidates are blue compact dwarf galaxies, and 24 of them have either cometary shape or are formed by chained knots.

Abstract Copyright: ∼

Journal keyword(s): galaxies: abundances - galaxies: formation - galaxies: starburst - galaxies: statistics - methods: data analysis

VizieR on-line data: <Available at CDS (J/ApJ/743/77): table1.dat table2.dat>

CDS comments: Object SDSS J015809.39+000637.2 in Table 1 is a misprint for SDSS J015809.38-000637.2

Simbad objects: 132

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Number of rows : 132
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 UGC 12894 G 00 00 22.55 +39 29 43.5   17       ~ 36 0
2 AGC 103435 LSB 00 15 20.679 +01 04 36.99           ~ 17 0
3 SDSS J001628.25+010801.9 G 00 16 28.254 +01 08 01.92           ~ 4 0
4 HS 0017+1055 AG? 00 20 21.40 +11 12 21.0           ~ 20 0
5 SDSS J002904.70-010825.9 AG? 00 29 04.706 -01 08 25.96   19.315   18.865   ~ 6 0
6 SDSS J002949.49-002539.8 G 00 29 49.497 -00 25 39.89           ~ 4 0
7 ESO 473-24 AG? 00 31 22.51 -22 45 57.5   16.11   15.87 17.7 ~ 58 1
8 SDSS J003630.40+005234.7 G 00 36 30.411 +00 52 34.78           ~ 7 0
9 NAME Andromeda IV G 00 42 32.3 +40 34 19           ~ 79 0
10 SDSS J005712.60-002157.6 EmG 00 57 12.603 -00 21 57.67           ~ 5 0
11 IC 1613 GiC 01 04 48.4071 +02 07 10.185   10.42 10.01 9.77   ~ 1236 2
12 SDSS J010750.81+000128.3 G 01 07 50.817 +00 01 28.42           ~ 4 0
13 LEDA 166061 AG? 01 08 21.93 -38 12 34.5           ~ 30 0
14 UGC 772 LSB 01 13 40.450 +00 52 39.16   17       ~ 63 0
15 SDSS J011914.28-093546.4 EmG 01 19 14.283 -09 35 46.23           ~ 18 0
16 UGC 993 H2G 01 25 34.1903008704 +07 59 24.703412028   15.6       ~ 44 0
17 SDSS J012646.11-003838.8 G 01 26 46.119 -00 38 38.86           ~ 3 0
18 SDSS J013352.55+134209.5 EmG 01 33 52.555 +13 42 09.53           ~ 20 0
19 SDSS J013544.03-002316.8 AG? 01 35 44.041 -00 23 16.67           ~ 7 0
20 UGCA 20 bCG 01 43 14.6 +19 58 51   16       ~ 55 0
21 Z 412-24 H2G 01 44 41.3 +04 53 26 15.07 15.50 15.16 14.86 14.58 ~ 99 0
22 LEDA 7422 EmG 01 58 09.3923460120 -00 06 37.007607240           ~ 30 0
23 LEDA 166065 G 02 00 10.2 +28 49 53   17.2       ~ 63 0
24 LEDA 7896 AG? 02 04 25.598 -10 09 35.01   17       ~ 18 0
25 MCG-02-06-026 AG? 02 05 49.081 -09 49 17.62   15.14   16.77 15.2 ~ 35 0
26 [GPM2009] 096632 EmG 02 51 47.5 -30 06 32           ~ 3 0
27 SDSS J025428.94+003550.4 G 02 54 28.94 +00 35 50.4           ~ 5 0
28 SDSS J030149.01-005257.4 EmG 03 01 49.026 -00 52 57.39           ~ 11 0
29 SDSS J030331.27-010947.1 G 03 03 31.270 -01 09 47.11           ~ 4 0
30 SDSS J031300.04+000612.1 EmG 03 13 00.0482488680 +00 06 12.230652204           ~ 4 0
31 SDSS J031301.57+001040.2 AG? 03 13 01.57 +00 10 40.3           ~ 4 0
32 UGC 2684 AG? 03 20 23.71 +17 17 45.1   18       ~ 77 0
33 [PBT2001] SBSG 0335-052 W G 03 37 38.40 -05 02 37.5   19.14     18.85 ~ 107 1
34 SBSG 0335-052B G 03 37 44.04 -05 02 40.2   16.77 16.65   16.79 ~ 185 1
35 [GPM2009] J0338+0013 EmG 03 38 12.2 +00 13 13           ~ 4 0
36 ESO 358-60 GiC 03 45 12.14 -35 34 15.3   15.86   15.46 16.6 ~ 73 0
37 [GPM2009] G0405204-364859 BG EmG 04 05 18.6 -36 48 49           ~ 3 0
38 [GPM2009] J0519+0007 G 05 19 02.6953532514 +00 07 29.106797166           ~ 22 0
39 SCHG 0618-402 H2G 06 20 03.8353 -40 16 42.997           ~ 26 0
40 ESO 489-56 AG? 06 26 17.4435 -26 16 01.290   16.69   16.28 15.0 ~ 58 0
41 SDSS J080840.84+172856.4 G 08 08 40.8480324624 +17 28 56.462019456           ~ 8 0
42 SDSS J081239.52+483645.3 bCG 08 12 39.532 +48 36 45.27           ~ 24 0
43 UGC 4305 IG 08 19 04.9864630512 +70 43 13.086910452 12.06 11.72 11.39 11.11   ~ 769 2
44 SDSS J082540.44+184617.2 EmG 08 25 40.4479904808 +18 46 17.179801968           ~ 5 0
45 LEDA 2790884 bCG 08 25 55.5166210656 +35 32 31.833368556   18.2       ~ 120 1
46 UGC 4459 GiG 08 34 07.20 +66 10 54.0 15.39 15.03 14.70 14.49   ~ 338 2
47 UGC 4483 GiG 08 37 03.00 +69 46 31.0 15.70 15.46 14.98 14.89   ~ 303 0
48 US 1442 Sy1 08 40 29.9112912216 +47 07 10.241384412   18.2       ~ 62 0
49 SDSS J084236.57+103313.9 EmG 08 42 36.5888720088 +10 33 13.911978708           ~ 21 0
50 LEDA 2790886 EmG 08 49 40.3214491272 +35 11 38.002195500   19.0       ~ 10 0
51 SDSS J091028.77+071117.9 H2G 09 10 28.7687526264 +07 11 18.149714808           ~ 8 0
52 SDSS J091159.43+313535.9 AG? 09 11 59.434 +31 35 35.92           ~ 14 0
53 LEDA 4015419 LSB 09 26 10.3 +33 43 15           ~ 30 0
54 Mrk 116A G 09 34 01.9716600456 +55 14 27.789835056           ~ 35 0
55 Mrk 116 PaG 09 34 02.1 +55 14 25           ~ 1106 1
56 LEDA 27591 SBG 09 40 12.843 +29 35 30.30   16.32 16.08     ~ 57 0
57 SDSS J094254.27+340411.9 EmG 09 42 54.2685704616 +34 04 12.207354168           ~ 6 0
58 MCG+00-25-010 Sy1 09 44 01.8742171440 -00 38 31.993352700   15.5       ~ 70 0
59 LEDA 27886 QSO 09 44 17.101 +54 11 28.83   19.5       ~ 71 0
60 Cambridge 0953-174 H2G 09 55 22.7 -17 38 15           ~ 2 0
61 UGC 5340 AG? 09 56 46.047 +28 49 43.77 14.82 14.74 14.59 14.55   ~ 227 1
62 NAME Leo A G 09 59 26.46 +30 44 47.0 14.08 13.54 13.26 13.33   ~ 615 0
63 NAME Sextans B H2G 10 00 00.8217342072 +05 20 09.533389560 12.77 12.25 11.89 11.71   ~ 528 0
64 LEDA 2790903 EmG 10 03 48.6589266552 +45 04 57.692107308   17.7       ~ 13 0
65 NAME Sex A H2G 10 11 00.5 -04 41 30 12.48 12.13 11.93 11.78   ~ 727 2
66 LEDA 29998 EmG 10 16 24.516 +37 54 45.96   16.5       ~ 52 0
67 2MASS J10253030+1402078 Sy1 10 25 30.2923813752 +14 02 07.394019972   20.59 19.77     ~ 9 0
68 Mrk 32 AG? 10 27 01.7018076288 +56 16 14.337853680   16.5       ~ 36 0
69 SDSS J103137.27+043422.0 GiP 10 31 37.2791738640 +04 34 22.224457776           ~ 7 0
70 SDSS J103137.28+043422.0 G 10 31 37.28 +04 34 22.0           ~ 3 0
71 LEDA 2302764 EmG 10 36 25.010 +47 41 53.69   18.5       ~ 16 0
72 [ITS2007] 52339-578-60 EmG 10 44 57.797 +03 53 13.15           ~ 48 0
73 LEDA 2147507 EmG 11 02 09.80160 +39 18 45.3960   18.20 17.7     ~ 11 0
74 MCG+10-16-059 AG? 11 05 53.6921585616 +60 22 28.499349252   16       ~ 24 0
75 NAME Arp's Galaxy AG? 11 19 34.344 +51 30 12.17   17.3       ~ 71 0
76 SDSS J112152.80+032421.2 G 11 21 52.888 +03 24 21.19           ~ 8 0
77 UGC 6456 bCG 11 27 59.90 +78 59 39.0   14.50       ~ 335 1
78 MCG+10-17-011 AG? 11 32 02.6164558680 +57 22 36.292387908   17       ~ 59 1
79 LEDA 2368928 H2G 11 45 06.261 +50 18 02.40           ~ 14 0
80 2dFGRS TGN242Z154 G 11 51 32.9385144552 -02 22 21.992743236   16.234   15.676   ~ 8 0
81 LEDA 2543081 LSB 11 57 54.213 +56 38 16.77           ~ 27 0
82 LEDA 3120683 EmG 12 01 22.3051558008 +02 11 08.574134388           ~ 40 0
83 LEDA 2815986 AG? 12 02 02.4750603336 +54 15 51.049196784   18.0       ~ 76 0
84 LEDA 39055 EmG 12 14 02.4588226248 +53 45 17.525587212   18       ~ 83 0
85 LEDA 39402 H2G 12 17 17.093 -28 02 32.67   17       ~ 135 0
86 LEDA 39845 GiC 12 20 40.2711363504 +13 53 22.758646344   17.5       ~ 54 0
87 LEDA 101471 EmG 12 24 36.7369432538 +37 24 35.833921444           ~ 36 0
88 ESO 380-27 H2G 12 25 46.95 -36 14 00.7   17.47   16.52   ~ 100 1
89 RMB 132 bCG 12 30 48.6089418912 +12 02 42.805457196     16.78   16.44 ~ 99 0
90 CAIRNS J123718.50+291454.7 EmG 12 37 18.50 +29 14 54.7   19.91 19.78     ~ 12 0
91 NAME CVn I dwA GiC 12 38 40.06 +32 46 00.5 16.91 16.66 16.73 16.62   ~ 232 0
92 2MASX J12390403+3920437 H2G 12 39 04.0340323080 +39 20 43.370050560   18.7       ~ 27 0
93 SDSS J123944.58+145612.8 G 12 39 44.5858152072 +14 56 12.569226936           ~ 4 0
94 LEDA 2790846 EmG 12 51 52.4 +49 03 25   18.0       ~ 54 0
95 2QZ J125526.0-021334 Sy1 12 55 26.0736176088 -02 13 34.103615484     19.46     ~ 5 0
96 UGC 8091 H2G 12 58 40.1930636208 +14 13 00.739589628 15.24 15.16 14.98 14.81   ~ 463 0
97 KISS F1312-2143 EmG 13 13 16.4 +44 02 30           ~ 11 0
98 UGC 8308 AG? 13 13 22.839 +46 19 21.71   17       ~ 131 1
99 LEDA 169741 H2G 13 21 19.6991553744 +32 08 24.832025232   19.123       ~ 28 0
100 2QZ J132347.5-013252 EmG 13 23 47.4573498792 -01 32 52.048078188           ~ 40 0
101 SDSS J132723.28+402204.1 EmG 13 27 23.285 +40 22 04.18           ~ 7 0
102 [ITS2007] 53091-1464-370 EmG 13 31 26.9314785720 +41 51 48.242294892           ~ 11 0
103 ESO 577-27 EmG 13 42 46.5208 -19 34 48.106   16.42   16.16   ~ 18 0
104 SDSS J135525.66+465151.3 EmG 13 55 25.6612180368 +46 51 51.397156440           ~ 6 0
105 2dFGRS TGN206Z232 bCG 14 14 54.149 -02 08 22.92   18.065   17.598   ~ 23 0
106 MCG+07-29-060 QSO 14 17 01.716 +43 30 13.52   15.6       ~ 172 0
107 SDSS J141851.12+210239.6 EmG 14 18 51.1291286064 +21 02 39.969779388           ~ 31 0
108 SDSS J142250.72+514516.5 G 14 22 50.72 +51 45 16.5           ~ 4 0
109 [MWC2015] B1422+231 21070 AGN 14 23 42.8690848464 +22 57 28.802400660           ~ 14 0
110 SDSS J144158.31+291434.2 G 14 41 58.32 +29 14 34.2           ~ 4 0
111 UGC 9497 H2G 14 44 12.8032800372 +42 37 43.773570223   16.0       ~ 82 0
112 LEDA 101527 EmG 15 09 34.174 +37 31 46.12   17.9       ~ 26 0
113 KISSB 186 SBG 15 15 42.5 +29 01 40   19.83 19.42     ~ 13 0
114 KISS F1615-4535 SBG 16 16 38.894 +29 03 32.46   17.79 17.38     ~ 16 0
115 SDSS J164402.63+273405.4 G 16 44 02.631 +27 34 05.47           ~ 4 0
116 [ITS2007] 53149-1570-21 H2G 16 47 10.6644029376 +21 05 14.719155864           ~ 8 0
117 WISEP J170233.53+180306.4 MIR 17 02 33.534 +18 03 06.44   18.39       ~ 6 0
118 LEDA 2790946 EmG 17 05 45.3265183560 +43 28 49.507838940   18.1       ~ 13 0
119 NAME Sgr dIG G 19 29 59.0 -17 40 41   15.5 13.6     ~ 307 1
120 SDSS J205312.59+003914.2 G 20 53 12.597 +00 39 14.25           ~ 5 0
121 SDSS J210455.31-003522.3 G 21 04 55.310 -00 35 22.38           ~ 31 0
122 SDSS J212025.93-005826.5 AG? 21 20 25.940 -00 58 26.35           ~ 7 0
123 SDSS J213658.81+041404.0 bCG 21 36 58.82310 +04 14 04.0999           ~ 12 0
124 SDSS J215031.95+003305.1 G 21 50 31.957 +00 33 05.07           ~ 4 0
125 ESO 146-14 AG? 22 12 59.80 -62 04 05.9   15.17   14.77 14.1 ~ 69 0
126 2dFGRS TGS116Z004 G 22 13 26.1 -25 26 43   18.282   18.182   ~ 4 0
127 NAME Kinman Dwarf bCG 22 30 36.7959714600 -00 06 36.924915456 16.85 17.35 16.87   16.65 ~ 65 2
128 2dFGRS TGS258Z058 G 22 37 02.29 -28 52 43.7   19.218   19.141   ~ 4 0
129 HS 2236+1344 bCG 22 38 31.1192205216 +14 00 29.770282476           ~ 37 0
130 SDSS J225059.27+000032.8 G 22 50 59.27243 +00 00 32.7241           ~ 4 0
131 SDSS J225900.86+141343.5 G 22 59 00.8645360880 +14 13 43.518344988           ~ 4 0
132 EQ J2302+0049 EmG 23 02 09.9920201040 +00 49 39.019513008           ~ 19 0

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