TY - JOUR
T1 - HYDROGEN EMISSION from the IONIZED GASEOUS HALOS of LOW-REDSHIFT GALAXIES
AU - Zhang, Huanian
AU - Zaritsky, Dennis
AU - Zhu, Guangtun
AU - Ménard, Brice
AU - Hogg, David W.
N1 - Funding Information:
D.Z. acknowledges financial support from NASA ADAP NNX12AE27G and NSF grant AST-1311326. B.M. acknowledges support from NSF-1313302. The authors gratefully acknowledge the SDSS III team for providing a valuable resource to the community.
Publisher Copyright:
© 2016. The American Astronomical Society. All rights reserved..
PY - 2016/12/20
Y1 - 2016/12/20
N2 - Using a sample of nearly half a million galaxies, intersected by over 7 million lines of sight from the Sloan Digital Sky Survey Data Release 12, we trace Hα + [N ii] emission from a galactocentric projected radius, r p, of 5 kpc to more than 100 kpc. The emission flux surface brightness is ∞rp-1.9± 0.4. We obtain consistent results using only the Hα or [N ii] flux. We measure a stronger signal for the bluer half of the target sample than for the redder half on small scales, r p < 20 kpc. We obtain a 3σ detection of Hα + [N ii] emission in the 50-100 kpc r p bin. The mean emission flux within this bin is (1.10 ± 0.35) ×10-20 erg cm-2 s-1 Å-1, which corresponds to 1.87 ×10-20 erg cm-2 s-1 arcsec-2 or 0.0033 Rayleigh. This detection is 34 times fainter than a previous strict limit obtained using deep narrow-band imaging. The faintness of the signal demonstrates why it has been so difficult to trace recombination radiation out to large radii around galaxies. This signal, combined with published estimates of n H, leads us to estimate the temperature of the gas to be 12,000 K, consistent with independent empirical estimates based on metal ion absorption lines and expectations from numerical simulations.
AB - Using a sample of nearly half a million galaxies, intersected by over 7 million lines of sight from the Sloan Digital Sky Survey Data Release 12, we trace Hα + [N ii] emission from a galactocentric projected radius, r p, of 5 kpc to more than 100 kpc. The emission flux surface brightness is ∞rp-1.9± 0.4. We obtain consistent results using only the Hα or [N ii] flux. We measure a stronger signal for the bluer half of the target sample than for the redder half on small scales, r p < 20 kpc. We obtain a 3σ detection of Hα + [N ii] emission in the 50-100 kpc r p bin. The mean emission flux within this bin is (1.10 ± 0.35) ×10-20 erg cm-2 s-1 Å-1, which corresponds to 1.87 ×10-20 erg cm-2 s-1 arcsec-2 or 0.0033 Rayleigh. This detection is 34 times fainter than a previous strict limit obtained using deep narrow-band imaging. The faintness of the signal demonstrates why it has been so difficult to trace recombination radiation out to large radii around galaxies. This signal, combined with published estimates of n H, leads us to estimate the temperature of the gas to be 12,000 K, consistent with independent empirical estimates based on metal ion absorption lines and expectations from numerical simulations.
KW - galaxies: ISM
KW - galaxies: halos
KW - galaxies: kinematics and dynamics
KW - galaxies: structure
KW - intergalactic medium
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U2 - 10.3847/1538-4357/833/2/276
DO - 10.3847/1538-4357/833/2/276
M3 - Article
AN - SCOPUS:85007569672
SN - 0004-637X
VL - 833
JO - Astrophysical Journal
JF - Astrophysical Journal
IS - 2
M1 - 276
ER -