TY - JOUR
T1 - A plethora of active galactic nuclei among Lyα galaxies at low redshift
AU - Finkelstein, Steven L.
AU - Cohen, Seth H.
AU - Malhotra, Sangeeta
AU - Rhoads, James E.
AU - Papovich, Casey
AU - Zheng, Zhenya
AU - Wang, Jun Xian
PY - 2009
Y1 - 2009
N2 - We investigate the fraction of z ∼ 0.3 Lyα emitting galaxies (LAEs), which host active galactic nucleus (AGN) activity, which is typically from 1% to 5% at 2 ≲z≲ 6. Using optical spectroscopy of 23 LAEs at 0.2 ≤z≤ 0.45 selected with Galaxy Evolution Explorer (GALEX) UV data, we probe for AGNs with a variety of methods, including line widths, diagnostic line ratios, high-ionization emission, infrared activity, and X-ray luminosity. We found that our sample of low-redshift LAEs has an AGN fraction of 43 +18 -26%, significantly higher than at high redshift. While previous results have shown that low-redshift LAEs have a lower space density than their high-redshift analogs, these results show that star-forming LAEs at low redshift are rarer still. Accounting for differences in available AGN classification methods, we conclude that rest-frame optical spectroscopy is necessary to identify low-luminosity AGNs in LAEs at high redshift, and that limits on the X-ray flux are necessary to determine the extent to which the AGN contaminates the Lyα fluxes.
AB - We investigate the fraction of z ∼ 0.3 Lyα emitting galaxies (LAEs), which host active galactic nucleus (AGN) activity, which is typically from 1% to 5% at 2 ≲z≲ 6. Using optical spectroscopy of 23 LAEs at 0.2 ≤z≤ 0.45 selected with Galaxy Evolution Explorer (GALEX) UV data, we probe for AGNs with a variety of methods, including line widths, diagnostic line ratios, high-ionization emission, infrared activity, and X-ray luminosity. We found that our sample of low-redshift LAEs has an AGN fraction of 43 +18 -26%, significantly higher than at high redshift. While previous results have shown that low-redshift LAEs have a lower space density than their high-redshift analogs, these results show that star-forming LAEs at low redshift are rarer still. Accounting for differences in available AGN classification methods, we conclude that rest-frame optical spectroscopy is necessary to identify low-luminosity AGNs in LAEs at high redshift, and that limits on the X-ray flux are necessary to determine the extent to which the AGN contaminates the Lyα fluxes.
KW - Galaxies: active
KW - Galaxies: evolution
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U2 - 10.1088/0004-637X/703/2/L162
DO - 10.1088/0004-637X/703/2/L162
M3 - Article
AN - SCOPUS:77949535543
SN - 0004-637X
VL - 703
SP - L162-L166
JO - Astrophysical Journal
JF - Astrophysical Journal
IS - 2 PART 2
ER -