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 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:
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FileName Lrecl Records Explanations
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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 2005ApJ...622L..73P) HeI emissivities
table5.dat 91 364 Parameters for the best solution for He mass
fraction in Table 3
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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
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Bytes Format Units Label Explanations
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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
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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)
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Byte-by-byte Description of file: sample2.dat
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Bytes Format Units Label Explanations
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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
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Note (1): Positions from SDSS DR6. 2 could not be found, and therefore have
no position: 51615-0266-100 and 52236-0740-259
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Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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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
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Note (1): Relative to 1/100 of the Hβ flux.
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Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
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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
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Note (2): In units of Angstroms.
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Byte-by-byte Description of file: table4.dat
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Bytes Format Units Label Explanations
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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
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Note (3): Abundances are calculated adopting Te=Te(OIII).
Note (4): Abundances are calculated adopting Te=Te(He+).
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Byte-by-byte Description of file: table5.dat
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Bytes Format Units Label Explanations
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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
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Table 3: Budget of Different Systematic Effects in the Yp Determination
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Property ΔYp
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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%
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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.
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History:
From electronic version of the journal
(End) Greg Schwarz [AAS], Patricia Vannier [CDS] 15-Apr-2009