J/ApJ/896/77 The PHLEK survey: oxygen & helium abundances (Hsyu+, 2020)
The PHLEK survey: a new determination of the primordial helium abundance.
Hsyu T., Cooke R.J., Prochaska J.X., Bolte M.
<Astrophys. J., 896, 77 (2020)>
=2020ApJ...896...77H 2020ApJ...896...77H
ADC_Keywords: Galaxies, spectra; Infrared; Optical; Abundances; H II regions
Keywords: Dwarf galaxies ; Galaxy abundances ; Galaxy chemical evolution ;
Big Bang nucleosynthesis
Abstract:
We present Keck NIRSPEC and Keck NIRES spectroscopy of sixteen
metal-poor galaxies that have pre-existing optical observations. The
near-infrared (NIR) spectroscopy specifically targets the
HeIλ10830Å emission line, due to its sensitivity to the
physical conditions of the gas in HII regions. We use these NIR
observations, combined with optical spectroscopy, to determine the
helium abundance of sixteen galaxies across a metallicity range
12+log10(O/H)=7.13-8.00. This data set is combined with two other
samples where metallicity and helium abundance measurements can be
secured: star-forming galaxies selected from the Sloan Digital Sky
Survey spectroscopic database, and existing low-metallicity systems in
the literature. We calculate a linear fit to these measurements,
accounting for intrinsic scatter, and report a new determination of
the primordial helium number abundance, yP=0.0805-0.0017+0.0017,
which corresponds to a primordial helium mass fraction
YP=0.2436-0.0040+0.0039. Using our determination of the
primordial helium abundance in combination with the latest primordial
deuterium measurement, (D/H)Px105=2.527±0.030, we place a bound
on the baryon density Ωbh2=0.0215-0.0005+0.0005 and the
effective number of neutrino species Neff=2.85-0.25+0.28. These
values are in 1.3σ agreement with those deduced from the Planck
satellite observations of the temperature fluctuations imprinted on
the cosmic microwave background.
Description:
We acquired optical and near-infrared spectra of metal-poor HII
regions in nearby dwarf galaxies using Keck Observatory. Spectroscopic
observations of our metal-poor galaxy sample took place during
semesters 2015B, 2016A, and 2018A (program IDs: U052LA/U052NI,
U091LA/U091NS, U172).
Optical spectroscopic observations of 32 metal-poor systems were made
using the Low Resolution Imaging Spectrometer (LRIS) with the
atmospheric dispersion corrector (ADC) at the W.M. Keck Observatory.
We acquired complementary NIR observations for 16 of our 32 galaxies
with optical spectroscopy. NIR observations were made using NIRSPEC in
semesters 2015B and 2016A and the Near-Infrared Echellette
Spectrometer (NIRES) in 2018A.
We supplement our data set with galaxies from the SDSS spectroscopic
database and the HeBCD sample from Izotov & Thuan (2004, J/ApJ/602/200)
and Izotov+ (2007ApJ...665.1115I 2007ApJ...665.1115I), a fraction of which have follow-up
NIR observations reported in Izotov+ (2014MNRAS.445..778I 2014MNRAS.445..778I).
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table2.dat 48 16 Near-infrared emission line fluxes of HII regions
in our Primordial Helium Legacy Experiment with Keck
(PHLEK)
table4.dat 163 118 Best recovered parameters from MCMC analysis
table5.dat 139 118 Ionic and total abundances of oxygen and helium
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See also:
V/147 : The SDSS Photometric Catalogue, Release 12 (Alam+, 2015)
J/ApJ/602/200 : HII regions abundances in blue compact gal. (Izotov+, 2004)
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)
J/A+A/522/A26 : Fe Abundances in metal-poor stars (Sbordone+ 2010)
J/ApJ/734/82 : NIR spectroscopy of five dwarf galaxies (Izotov+, 2011)
J/MNRAS/448/2687 : Blue diffuse dwarf galaxies spectroscopy (James+, 2015)
J/A+A/582/A74 : WISE J072543.88-235119.7 line abundances (Spite+, 2015)
J/ApJ/819/73 : Metallicity evolution of COSMOS BCD sample (Lian+, 2016)
J/MNRAS/465/3977 : Blue diffuse dwarf galaxies (James+, 2017)
J/ApJ/847/38 : Extreme emission line galaxies at z≲0.05 (Yang+, 2017)
J/ApJ/863/134 : SDSS low-metallicity blue compact dwarf gal. (Hsyu+, 2018)
http://www.sdss.org/ : SDSS home page
Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
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1- 10 A10 --- Name Galaxy name
12- 17 F6.2 10-20W/m2 FHeI [8.3/380] HeIλ10830 flux
in 10-17erg/s/cm2 (1)
19- 23 F5.2 10-20W/m2 e_FHeI [0.38/14] FHeI uncertainty
25- 30 F6.2 10-20W/m2 FPgam [2.3/190] Pγ flux
in 10-17erg/s/cm2 (1)
32- 36 F5.2 10-20W/m2 e_FPgam [0.67/10] FPgam uncertainty
38- 42 F5.3 --- HeI/Pgam [1.8/4.7] FHeI to FPgam ratio
44- 48 F5.3 --- e_HeI/Pgam [0.046/0.46] HeI/Pgam uncertainty
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Note (1): Observed near-infrared emission line flux and emission line flux
ratios of 16 galaxies observed using NIRSPEC or NIRES at Keck
Observatory. The fluxes are integrated flux measurements in units of
10-17erg/s/cm2 and not corrected for reddening, which is a
parameter we solve for in the MCMC.
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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- 20 A20 --- ID Galaxy identifier
22- 28 F7.5 --- y+ [0.07/0.097] Singly ionized helium abundance
30- 36 F7.5 --- E_y+ [0.0007/0.011] Upper uncertainty in y+
38- 44 F7.5 --- e_y+ [0.00079/0.015] Lower uncertainty in y+
46- 50 I5 K Te [10370/17900] Electron temperature
52- 55 I4 K E_Te [440/2400] Upper uncertainty in Te
57- 60 I4 K e_Te [270/2400] Lower uncertainty in Te
62- 66 F5.3 [cm-3] logNe [0.4/2.8] log electron density
68- 72 F5.3 [cm-3] E_logNe [0.083/1.1] Upper uncertainty in logNe
74- 78 F5.3 [cm-3] e_logNe [0.087/1.5] Lower uncertainty in logNe
80- 85 F6.4 --- cHb [0.004/0.48] Hβ reddening parameter
87- 92 F6.4 --- E_cHb [0.0065/0.14] Upper uncertainty in cHb
94- 99 F6.4 --- e_cHb [0.003/0.14] Lower uncertainty in cHb
101-104 F4.2 0.1nm aH [0.27/7] Underlying hydrogen stellar absorption
106-109 F4.2 0.1nm E_aH [0.3/2.1] Upper uncertainty in aH
111-114 F4.2 0.1nm e_aH [0.2/1.9] Lower uncertainty in aH
116-120 F5.3 0.1nm aHe [0.1/1.16] Underlying helium stellar absorption
122-126 F5.3 0.1nm E_aHe [0.06/0.6] Upper uncertainty in aHe
128-132 F5.3 0.1nm e_aHe [0.063/0.5] Lower uncertainty in aHe
134-137 F4.2 --- tauHe [0.29/3.8] Helium optical depth parameter
139-142 F4.2 --- E_tauHe [0.29/1.8] Upper uncertainty in tauHe
144-147 F4.2 --- e_tauHe [0.21/1.7] Lower uncertainty in tauHe
149-153 F5.2 [-] logxi [-4.71/-1] log ratio of neutral to
singly ionized hydrogen density
155-158 F4.2 [-] E_logxi [0.65/2] Upper uncertainty in logxi
160-163 F4.2 [-] e_logxi [0.87/2.97] Lower uncertainty in logxi
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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- 20 A20 --- ID Galaxy identifier
22- 26 F5.3 10-5 O+/H+ [0.43/7.5] Singly ionized Oxygen abundance
28- 32 F5.3 10-5 E_O+/H+ [0.05/1.4] Upper uncertainty in O+/H+
34- 38 F5.3 10-5 e_O+/H+ [0.04/1.2] Lower uncertainty in O+/H+
40- 44 F5.2 10-5 O++/H+ [0.6/15.7] Doubly ionized Oxygen abundance
46- 49 F4.2 10-5 E_O++/H+ [0.26/4.8] Upper uncertainty in O++/H+
51- 54 F4.2 10-5 e_O++/H+ [0.15/4] Lower uncertainty in O++/H+
56- 60 F5.2 10-5 O/H [1.73/18.3] Total Oxygen abundance
62- 65 F4.2 10-5 E_O/H [0.39/4.8] Upper uncertainty in O/H
67- 70 F4.2 10-5 e_O/H [0.25/4] Lower uncertainty in O/H
72- 78 F7.5 --- y+ [0.07/0.097] Singly ionized Helium abundance
80- 86 F7.5 --- E_y+ [0.00072/0.011] Upper uncertainty in y+
88- 94 F7.5 --- e_y+ [0.00079/0.015] Lower uncertainty in y+
96-101 F6.4 --- y++ [0/0.003] Doubly ionized Helium abundance
103-108 F6.4 --- E_y++ [0/0.0009] Upper uncertainty in y++
110-115 F6.4 --- e_y++ [0/0.0008] Lower uncertainty in y++
117-123 F7.5 --- y [0.07/0.097] Total Helium abundance
125-131 F7.5 --- E_y [0.00072/0.011] Upper uncertainty in y
133-139 F7.5 --- e_y [0.00079/0.015] Lower uncertainty in y
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History:
From electronic version of the journal
(End) Prepared by [AAS], Emmanuelle Perret [CDS] 22-Oct-2021