J/A+A/546/A122 SDSS extremely metal-poor emission-line galaxies (Izotov+, 2012)
Hunting for extremely metal-poor emission-line galaxies in the Sloan Digital
Sky Survey: MMT and 3.5 M. APO observations.
Izotov Y.I., Thuan T.X., Guseva N.G.
<Astron. Astrophys., 546, A122-122 (2012)>
=2012A&A...546A.122I 2012A&A...546A.122I
ADC_Keywords: H II regions ; Abundances ; Equivalent widths
Keywords: galaxies: abundances - galaxies: irregular - galaxies: evolution -
galaxies: ISM - HII regions - ISM: abundances
Abstract:
We present 6.5-m MMT and 3.5m APO spectrophotometry of 69 HII
regions in 42 low-metallicity emission-line galaxies, selected from
the data release 7 of the Sloan Digital Sky Survey to have mostly
[OIII]λ4959/Hβ≲1 and [NII]λ6583/Hβ≲0.1.
The electron temperature-sensitive emission line [OIII]λ4363 is
detected in 53 HII regions allowing a direct abundance determination.
The oxygen abundance in the remaining 16 HII regions is derived using
a semi-empirical method. The oxygen abundance of the galaxies in our
sample ranges from 12+logO/H∼7.1 to ∼7.9, with 14 HII regions in 7
galaxies with 12+logO/H≤7.35. In 5 of the latter galaxies, the
oxygen abundance is derived here for the first time. Including other
known extremely metal-deficient emission-line galaxies from the
literature, e.g. SBS 0335-052W, SBS 0335-052E and I Zw 18, we
have compiled a sample of the 17 most metal-deficient (with
12+logO/H≤7.35) emission-line galaxies known in the local universe.
There appears to be a metallicity floor at 12+log O/H∼6.9, suggesting
that the matter from which dwarf emission-line galaxies formed was
pre-enriched to that level by e.g. Population III stars.
Description:
New optical spectra were obtained for a subsample of galaxies using
the 3.5m APO telescope in the course of several nights during the
February 2008-February 2009 period.
The MMT spectrophotometric observations were obtained on the nights of
2008 March 28-29, and 2010 April 13.
File Summary:
--------------------------------------------------------------------------------
FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
table1.dat 96 74 General characteristics of galaxies
table3a.dat 47 862 Emission line intensities in 3.5m APO spectra
table3b.dat 40 39 Hβ parameters for 3.5m APO spectra
table4a.dat 47 740 Emission line intensities in low-resolution MMT
spectra
table4b.dat 40 20 Hβ parameters for low-resolution MMT spectra
table5a.dat 47 165 Emission line intensities in medium-resolution
MMT spectra
table5b.dat 40 12 Hβ parameters for medium-resolution MMT
spectra
table6.dat 64 543 Ionic and total heavy element abundances derived
from 3.5m APO spectra
table7.dat 64 456 Ionic and total heavy element abundances derived
from the low-resolution MMT spectra
table8.dat 64 102 Ionic and total heavy element abundances derived
from the high-resolution MMT spectra
--------------------------------------------------------------------------------
See also:
J/ApJ/511/639 : Abundances in blue compact galaxies (Izotov+, 1999)
J/ApJ/602/200 : HII regions abundances in blue compact galaxies (Izotov+ 2004)
J/ApJS/161/240 : High-ionization emission in metal-deficient BCDs (Thuan+ 2005)
J/A+A/448/955 : Abundances of emission galaxies in SDSS-DR3 (Izotov+, 2006)
J/ApJ/662/15 : Abundances in extragalactic HII regions (Izotov+, 2007)
Byte-by-byte Description of file: table1.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1 A1 --- Sam [abc] Sample (1)
3- 16 A14 --- Galaxy Galaxy name
19- 20 I2 h RAh Right ascension (J2000)
22- 23 I2 min RAm Right ascension (J2000)
25- 29 F5.2 s RAs Right ascension (J2000)
31 A1 --- DE- Declination sign (J2000)
32- 33 I2 deg DEd Declination (J2000)
35- 36 I2 arcmin DEm Declination (J2000)
38- 42 F5.2 arcsec DEs Declination (J2000)
44- 50 F7.5 --- z Redshift
52- 57 F6.2 Mpc Dist Distance
59 A1 --- Band [Bg] Band (SDSS g or B)
61- 65 F5.2 mag mag B or g magnitude
67- 70 F4.2 mag e_mag rms uncertainty on mag
72- 94 A23 --- OName Other names
96 I1 --- Ref ? Reference (2)
--------------------------------------------------------------------------------
Note (1): Samples as follows:
a = 3.5m Apache Point Observatory (APO) observations
b = low-resolution Multiple Mirror Telescope (MMT) observations
c = medium-resolution MMT observations
Note (2): References on the photometric data as follows:
1 = SDSS , http://www.sdss.org
2 = Patterson & Thuan (1996ApJS..107..103P 1996ApJS..107..103P)
3 = Makarova et al. (2009MNRAS.397.1672M 2009MNRAS.397.1672M)
4 = Karachentsev et al. (2004, Cat. J/AJ/127/2031)
5 = de Vaucouleurs et al. (1991, RC3, Cat. VII/155)
6 = Doyle et al. (2005MNRAS.361...34D 2005MNRAS.361...34D)
7 = Odewahn & Aldering (1995, Cat. VII/204)
--------------------------------------------------------------------------------
Byte-by-byte Description of file: table3a.dat table4a.dat table5a.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 14 A14 --- Galaxy Galaxy name
16- 19 I4 0.1nm lambda Wavelength
21- 30 A10 --- Ion Ion designation
36- 41 F6.2 --- I(lambda) ? Emission line intensity [I(Hβ)=100]
43- 47 F5.2 --- e_I(lambda) ? rms uncertainty on I(lambda)
--------------------------------------------------------------------------------
Byte-by-byte Description of file: table3b.dat table4b.dat table5b.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 14 A14 --- Galaxy Galaxy name
18- 22 F5.3 --- C(Hb) Hβ extinction coefficient
24- 29 F6.2 10-19W/m2 F(Hb) Uncorrected Hβ flux
31- 35 F5.1 0.1nm EW(Hb) Hβ equivalent width
37- 40 F4.2 0.1nm EW(abs) Equivalent width of the hydrogen absorption
stellar lines
--------------------------------------------------------------------------------
Byte-by-byte Description of file: table6.dat table7.dat table8.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 14 A14 --- Galaxy Galaxy name
15 A1 --- Met [ab] Method: a=direct, b=semi-empirical
19- 39 A21 --- Param Property name
47- 55 F9.3 --- Value Param value
57- 64 F8.3 ---- e_Value ? rms uncertainty on value
--------------------------------------------------------------------------------
History:
From electronic version of the journal
(End) Patricia Vannier [CDS] 12-Dec-2012