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J/ApJ/662/15   Abundances in extragalactic HII regions       (Izotov+, 2007)

The primordial abundance of 4He: a self-consistent empirical analysis of systematic effects in a large sample of low-metallicity H II regions. Izotov Y.I., Thuan T.X., Stasinska G. <Astrophys. J., 662, 15-38 (2007)> =2007ApJ...662...15I
ADC_Keywords: H II regions ; Abundances ; Equivalent widths Keywords: galaxies: abundances - galaxies: irregular - galaxies: ISM - H II regions - ISM: abundances Abstract: We determine the primordial helium mass fraction Yp using 93 spectra of 86 low-metallicity extragalactic HII regions. This sample constitutes the largest and most homogeneous high-quality data set in existence for the determination of Yp. For comparison, and to improve the statistics in our investigation of systematic effects affecting the Yp determination, we have also considered a sample of 271 low-metallicity HII regions selected from Data Release 5 of the Sloan Digital Sky Survey. Although this larger sample shows more scatter, it gives results that are consistent at the 2σ level with our original sample. We have considered known systematic effects that may affect the 4He abundance determination. Description: We determine Yp and dY/dZ independently for two different samples. The HeBCD sample is composed of 93 different observations of 86 HII regions in 77 galaxies. This sample is essentially the same as the one described in Izotov & Thuan (2004, Cat. J/ApJ/602/200), except that two close pairs of HII regions in the spiral galaxy M1011 have been added. These four HII regions were observed with the 6.5m MMT on the night of 2004 February 20. File Summary:
FileName Lrecl Records Explanations
ReadMe 80 . This file sample1.dat 72 93 HeBCD sample list sample2.dat 70 271 SDSS DR5 sample list table1.dat 223 364 Emission line fluxes table2.dat 242 364 Emission line equivalent widths table4.dat 79 364 Oxygen, nitrogen and helium abundances for the best solutions with the Porter et al. (2005ApJ...622L..73P) HeI emissivities table5.dat 91 364 Parameters for the best solution for He mass fraction in Table 3
See also: J/ApJ/602/200 : HII regions abundances in blue compact galaxies (Izotov+ 2004) J/ApJS/170/251 : Multiplet table for 4He (Drake+, 2007) http://www.sdss.org/ : SDSS Home Page Byte-by-byte Description of file: sample1.dat
Bytes Format Units Label Explanations
1- 2 I2 h RAh Right ascension (J2000) 4- 5 I2 min RAm Right ascension (J2000) 7- 10 F4.1 s RAs Right ascension (J2000) 12 A1 --- DE- Declination sign (J2000) 13- 14 I2 deg DEd Declination (J2000) 16- 17 I2 arcmin DEm Declination (J2000) 19- 20 I2 arcsec DEs Declination (J2000) 21 A1 --- r_Pos [as*] Reference for position (1) 24- 47 A24 --- SName Simbad name 52- 72 A21 --- Name Name
Note (1): References as follows: a = Izotov & Thuan (2004, Cat. J/ApJ/602/200) * = this paper s = Simbad, from Simbad name (position of the galaxy)
Byte-by-byte Description of file: sample2.dat
Bytes Format Units Label Explanations
1- 14 A14 --- Name SDSS name (mjd-plate-fiber) (G1) 16- 24 F9.5 deg RAdeg ? Right ascension in decimal degrees (J2000) (1) 25- 33 F9.5 deg DEdeg ? Declination in decimal degrees (J2000) (1) 35- 40 F6.4 --- z ? Redshift
Note (1): Positions from SDSS DR6. 2 could not be found, and therefore have no position: 51615-0266-100 and 52236-0740-259
Byte-by-byte Description of file: table1.dat
Bytes Format Units Label Explanations
1- 21 A21 --- Name Object identification (G1) 23- 27 F5.1 --- OII-3727 ? The [OII] 3727 emission line flux (1) 29- 31 F3.1 --- e_OII-3727 ? Error in OII-3727 33- 35 F3.1 --- H12-3750 ? The H12 3750 emission line flux (1) 37- 39 F3.1 --- e_H12-3750 ? Error in H12-3750 41- 43 F3.1 --- H11-3771 ? The H11 3771 emission line flux (1) 45- 47 F3.1 --- e_H11-3771 ? Error in H11-3771 49- 51 F3.1 --- H10-3797 ? The H10 3797 emission line flux (1) 53- 55 F3.1 --- e_H10-3797 ? Error in H10-3797 57- 59 F3.1 --- H9-3835 ? The H9 3835 emission line flux (1) 61- 63 F3.1 --- e_H9-3835 ? Error in H9-3835 65- 68 F4.1 --- H8+HeI The H8+HeI 3889 emission line flux (1) 70- 72 F3.1 --- e_H8+HeI Error in H8+HeI 74- 77 F4.1 --- Hd-4102 The Hδ 4102 emission line flux (1) 79- 81 F3.1 --- e_Hd-4102 Error in Hd-4102 83- 86 F4.1 --- Hg-4340 The Hγ 4340 emission line flux (1) 88- 90 F3.1 --- e_Hg-4340 Error in Hg-4340 92- 95 F4.1 --- OIII-4363 The [OIII] 4363 emission line flux (1) 97- 99 F3.1 --- e_OIII-4363 Error in OIII-4363 101-103 F3.1 --- HeI-4471 The HeI 4471 emission line flux (1) 105-107 F3.1 --- e_HeI-4471 Error in HeI-4471 109-111 F3.1 --- HeII-4686 ? The HeII 4686 emission line flux (1) 113-115 F3.1 --- e_HeII-4686 ? Error in HeII-4686 117-121 F5.1 --- Hb-4861 The Hβ 4861 emission line flux (1) 123-125 F3.1 --- e_Hb-4861 Error in Hb-4861 127-131 F5.1 --- OIII-4959 The [OIII] 4959 emission line flux (1) 133-135 F3.1 --- e_OIII-4959 Error in OIII-4959 137-141 F5.1 --- OIII-5007 ? The [OIII] 5007 emission line flux (1) 143-145 F3.1 --- e_OIII-5007 ? Error in OIII-5007 147-150 F4.1 --- HeI-5876 The HeI 5876 emission line flux (1) 152-154 F3.1 --- e_HeI-5876 Error in HeI-5876 156-160 F5.1 --- Ha-6563 The Hα 6563 emission line flux (1) 162-164 F3.1 --- e_Ha-6563 Error in Ha-6563 166-169 F4.1 --- NII-6583 ? The [NII] 6583 emission line flux (1) 171-173 F3.1 --- e_NII-6583 ? Error in NII-6583 175-177 F3.1 --- HeI-6678 The HeI 6678 emission line flux (1) 179-181 F3.1 --- e_HeI-6678 Error in HeI-6678 183-186 F4.1 --- SII-6717 The [SII] 6717 emission line flux (1) 188-190 F3.1 --- e_SII-6717 Error in SII-6717 192-195 F4.1 --- SII-6731 The [SII] 6731 emission line flux (1) 197-199 F3.1 --- e_SII-6731 Error in SII-6731 201-203 F3.1 --- HeI-7065 The HeI 7065 emission line flux (1) 205-207 F3.1 --- e_HeI-7065 Error in HeI-7065 209-211 F3.1 --- OII-7320 ? The [OII] 7320 emission line flux (1) 213-215 F3.1 --- e_OII-7320 ? Error in OII-7320 217-219 F3.1 --- OII-7330 ? The [OII] 7330 emission line flux (1) 221-223 F3.1 --- e_OII-7330 ? Error in OII-7330
Note (1): Relative to 1/100 of the Hβ flux.
Byte-by-byte Description of file: table2.dat
Bytes Format Units Label Explanations
1- 21 A21 --- Name Object identification (G1) 23- 27 F5.1 0.1nm WOII-3727 ? The [OII] 3727 equivalent width (2) 29- 31 F3.1 0.1nm e_WOII-3727 ? Error in OII-3727 33- 35 F3.1 0.1nm WH12-3750 ? The H12 3750 equivalent width (2) 37- 39 F3.1 0.1nm e_WH12-3750 ? Error in H12-3750 41- 43 F3.1 0.1nm WH11-3771 ? The H11 3771 equivalent width (2) 45- 47 F3.1 0.1nm e_WH11-3771 ? Error in H11-3771 49- 52 F4.1 0.1nm WH10-3797 ? The H10 3797 equivalent width (2) 54- 56 F3.1 0.1nm e_WH10-3797 ? Error in H10-3797 58- 61 F4.1 0.1nm WH9-3835 ? The H9 3835 equivalent width (2) 63- 65 F3.1 0.1nm e_WH9-3835 ? Error in H9-3835 67- 70 F4.1 0.1nm WH8+HeI The H8+HeI 3889 equivalent width (2) 72- 74 F3.1 0.1nm e_WH8+HeI Error in H8+HeI 76- 79 F4.1 0.1nm WHd-4102 The Hδ 4102 equivalent width (2) 81- 83 F3.1 0.1nm e_WHd-4102 Error in Hd-4102 85- 89 F5.1 0.1nm WHg-4340 The Hγ 4340 equivalent width (2) 91- 93 F3.1 0.1nm e_WHg-4340 Error in Hg-4340 95- 98 F4.1 0.1nm WOIII-4363 The [OIII] 4363 equivalent width (2) 100-102 F3.1 0.1nm e_WOIII-4363 Error in OIII-4363 104-107 F4.1 0.1nm WHeI-4471 The HeI 4471 equivalent width (2) 109-111 F3.1 0.1nm e_WHeI-4471 Error in HeI-4471 113-116 F4.1 0.1nm WHeII-4686 ? The HeII 4686 equivalent width (2) 118-120 F3.1 0.1nm e_WHeII-4686 ? Error in HeII-4686 122-126 F5.1 0.1nm WHb-4861 The Hβ 4861 equivalent width (2) 128-131 F4.1 0.1nm e_WHb-4861 Error in Hb-4861 133-138 F6.1 0.1nm WOIII-4959 The [OIII] 4959 equivalent width (2) 140-143 F4.1 0.1nm e_WOIII-4959 Error in OIII-4959 145-150 F6.1 0.1nm WOIII-5007 ? The [OIII] 5007 equivalent width (2) 152-155 F4.1 0.1nm e_WOIII-5007 ? Error in OIII-5007 157-160 F4.1 0.1nm WHeI-5876 The HeI 5876 equivalent width (2) 162-164 F3.1 0.1nm e_WHeI-5876 Error in HeI-5876 166-171 F6.1 0.1nm WHa-6563 The Hα 6563 equivalent width (2) 173-177 F5.1 0.1nm e_WHa-6563 Error in Ha-6563 179-183 F5.1 0.1nm WNII-6583 ? The [NII] 6583 equivalent width (2) 185-187 F3.1 0.1nm e_WNII-6583 ? Error in NII-6583 189-192 F4.1 0.1nm WHeI-6678 The HeI 6678 equivalent width (2) 194-196 F3.1 0.1nm e_WHeI-6678 Error in HeI-6678 198-202 F5.1 0.1nm WSII-6717 The [SII] 6717 equivalent width (2) 204-206 F3.1 0.1nm e_WSII-6717 Error in SII-6717 208-211 F4.1 0.1nm WSII-6731 The [SII] 6731 equivalent width (2) 213-215 F3.1 0.1nm e_WSII-6731 Error in SII-6731 217-220 F4.1 0.1nm WHeI-7065 The HeI 7065 equivalent width (2) 222-224 F3.1 0.1nm e_WHeI-7065 Error in HeI-7065 226-229 F4.1 0.1nm WOII-7320 ? The [OII] 7320 equivalent width (2) 231-233 F3.1 0.1nm e_WOII-7320 ? Error in OII-7320 235-238 F4.1 0.1nm WOII-7330 ? The [OII] 7330 equivalent width (2) 240-242 F3.1 0.1nm e_WOII-7330 ? Error in OII-7330
Note (2): In units of Angstroms.
Byte-by-byte Description of file: table4.dat
Bytes Format Units Label Explanations
1- 21 A21 --- Name Object identification (G1) 23- 26 F4.1 10-5 (O/H)1 The O/H abundance ratio (3) 28- 30 F3.1 10-5 e_(O/H)1 Uncertainty in (O/H)1 32- 35 F4.1 10-5 (O/H)2 The O/H abundance ratio (4) 37- 39 F3.1 10-5 e_(O/H)2 Uncertainty in (O/H)2 41- 45 F5.1 10-7 (N/H)1 The N/H abundance ratio (3) 47- 50 F4.1 10-7 e_(N/H)1 Uncertainty in (N/H)1 52- 56 F5.1 10-7 (N/H)2 The N/H abundance ratio (4) 58- 61 F4.1 10-7 e_(N/H)2 Uncertainty in (N/H)2 63- 68 F6.4 --- Y The He mass fraction 70- 75 F6.4 --- e_Y Uncertainty in Y 77- 79 I3 0.1nm EWHb The Hβ equivalent width in Angstroms
Note (3): Abundances are calculated adopting Te=Te(OIII). Note (4): Abundances are calculated adopting Te=Te(He+).
Byte-by-byte Description of file: table5.dat
Bytes Format Units Label Explanations
1- 21 A21 --- Name Object identification (G1) 23- 26 F4.2 K TeOIII Electron temperature in the O III region 28- 31 F4.2 K e_TeOIII Uncertainty in TeOIII 33- 36 F4.2 K TeHe+ Electron temperature in the He+ region 38- 41 F4.2 K e_TeHe+ Uncertainty in TeHe+ 43- 45 I3 cm-3 Ne Electron density 47- 49 I3 cm-3 E_Ne Upper limit uncertainty in Ne 51- 53 I3 cm-3 e_Ne Lower limit uncertainty in Ne 55- 58 F4.2 --- tau Optical depth at 3889 Angstroms 60- 63 F4.2 --- E_tau Upper limit uncertainty in tau 65- 68 F4.2 --- e_tau Lower limit uncertainty in tau 70- 75 F6.4 --- DHa/Ha Fraction of Hα emission due to collisional excitation 77- 82 F6.4 --- ICF The ionization correction factor 84- 91 E8.2 --- chi2 The χ2min of the best solution
Table 3: Budget of Different Systematic Effects in the Yp Determination ----------------------------------------------------------------------- Property ΔYp ----------------------------------------------------------------------- HeI emissivity ~<+1.7% Te(He+)=(0.95-1.0)Te(OIII) ~←1.0% Underlying He I stellar absorption ~<+3.0% Collisional excitation of hydrogen emission lines ~<+1.0% ICF(He++He2+) ~←1.0% Global notes: Note (G1): The first 93 entries are HeBCD HII regions with names in alphabetical order. The remaining 271 entries are SDSS HII regions. Their names are in the format Xxxxx-yyyy-zzz, where Xxxxx is the middle Julian date (MJD) of the observation, yyyy is the plate number, and zzz is the fiber number, identified as [ITS2007] Xxxxx-yyyy-zzz in Simbad.
History: From electronic version of the journal
(End) Greg Schwarz [AAS], Patricia Vannier [CDS] 15-Apr-2009
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