Evidence for widespread active galactic nucleus activity among massive quiescent galaxies at z ~ 2
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Evidence for widespread active galactic nucleus activity among massive quiescent galaxies at z ~ 2. / Olsen, K.P.; Rasmussen, J.; Toft, S.; Zirm, A.W.
In: The Astrophysical Journal Letters, Vol. 764, No. 1, 4, 10.02.2013.Research output: Contribution to journal › Journal article › Research › peer-review
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T1 - Evidence for widespread active galactic nucleus activity among massive quiescent galaxies at z ~ 2
AU - Olsen, K.P.
AU - Rasmussen, J.
AU - Toft, S.
AU - Zirm, A.W.
PY - 2013/2/10
Y1 - 2013/2/10
N2 - We quantify the presence of active galactic nuclei (AGNs) in a mass-complete (M > 5 × 10 M ) sample of 123 star-forming and quiescent galaxies at 1.5 = z = 2.5, using X-ray data from the 4 Ms Chandra Deep Field-South (CDF-S) survey. 41% ± 7% of the galaxies are detected directly in X-rays, 22% ± 5% with rest-frame 0.5-8 keV luminosities consistent with hosting luminous AGNs (L > 3 × 10 erg s ). The latter fraction is similar for star-forming and quiescent galaxies, and does not depend on galaxy stellar mass, suggesting that perhaps luminous AGNs are triggered by external effects such as mergers. We detect significant mean X-ray signals in stacked images for both the individually non-detected star-forming and quiescent galaxies, with spectra consistent with star formation only and/or a low-luminosity AGN in both cases. Comparing star formation rates inferred from the 2-10 keV luminosities to those from rest-frame IR+UV emission, we find evidence for an X-ray excess indicative of low-luminosity AGNs. Among the quiescent galaxies, the excess suggests that as many as 70%-100% of these contain low- or high-luminosity AGNs, while the corresponding fraction is lower among star-forming galaxies (43%-65%). Our discovery of the ubiquity of AGNs in massive, quiescent z ~ 2 galaxies provides observational support for the importance of AGNs in impeding star formation during galaxy evolution.
AB - We quantify the presence of active galactic nuclei (AGNs) in a mass-complete (M > 5 × 10 M ) sample of 123 star-forming and quiescent galaxies at 1.5 = z = 2.5, using X-ray data from the 4 Ms Chandra Deep Field-South (CDF-S) survey. 41% ± 7% of the galaxies are detected directly in X-rays, 22% ± 5% with rest-frame 0.5-8 keV luminosities consistent with hosting luminous AGNs (L > 3 × 10 erg s ). The latter fraction is similar for star-forming and quiescent galaxies, and does not depend on galaxy stellar mass, suggesting that perhaps luminous AGNs are triggered by external effects such as mergers. We detect significant mean X-ray signals in stacked images for both the individually non-detected star-forming and quiescent galaxies, with spectra consistent with star formation only and/or a low-luminosity AGN in both cases. Comparing star formation rates inferred from the 2-10 keV luminosities to those from rest-frame IR+UV emission, we find evidence for an X-ray excess indicative of low-luminosity AGNs. Among the quiescent galaxies, the excess suggests that as many as 70%-100% of these contain low- or high-luminosity AGNs, while the corresponding fraction is lower among star-forming galaxies (43%-65%). Our discovery of the ubiquity of AGNs in massive, quiescent z ~ 2 galaxies provides observational support for the importance of AGNs in impeding star formation during galaxy evolution.
UR - http://www.scopus.com/inward/record.url?scp=84873965414&partnerID=8YFLogxK
U2 - 10.1088/0004-637X/764/1/4
DO - 10.1088/0004-637X/764/1/4
M3 - Journal article
AN - SCOPUS:84873965414
VL - 764
JO - Astrophysical Journal
JF - Astrophysical Journal
SN - 0004-637X
IS - 1
M1 - 4
ER -
ID: 45576205