We present results from a new ultra-deep \approx 400 ks Chandra observation of the SSA22 protocluster at z = 3.09 .
We have studied the X-ray properties of 234 z \sim 3 Lyman break galaxies ( LBGs ; protocluster and field ) and 158 z = 3.09 Ly \alpha emitters ( LAEs ) in SSA22 to measure the influence of the high-density protocluster environment on the accretion activity of supermassive black holes ( SMBHs ) in these UV-selected star forming populations .
We detect individually X-ray–emission from active galactic nuclei ( AGNs ) in six LBGs and five LAEs ; due to small overlap between the LBG and LAE source population , ten of these sources are unique .
At least six and potentially eight of these sources are members of the protocluster .
These sources have rest-frame 8–32 keV luminosities in the range of L _ { 8 - 32 ~ { } keV } = ( 3–50 ) \times 10 ^ { 43 } ergs s ^ { -1 } and an average observed-frame 2–8 keV to 0.5–2 keV band-ratio of \approx 0.8 ( mean effective photon index of \Gamma _ { eff } \approx 1.1 ) , suggesting significant absorption columns of N _ { H } \lower 2.15 pt \hbox { $ \buildrel > \over { \sim } $ } 10 ^ { 22 } – 10 ^ { 24 } cm ^ { -2 } .
We find that the fraction of LBGs and LAEs in the z = 3.09 protocluster harboring an AGN with L _ { 8 - 32 ~ { } keV } \lower 2.15 pt \hbox { $ \buildrel > \over { \sim } $ } 3 \times 10 ^ { 43 } ergs s ^ { -1 } is 9.5 ^ { +12.7 } _ { -6.1 } % and 5.1 ^ { +6.8 } _ { -3.3 } % , respectively .
These AGN fractions are somewhat larger ( by a mean factor of 6.1 ^ { +10.3 } _ { -3.6 } ; significant at the \approx 95 % confidence level ) than z \sim 3 sources found in lower-density “ field ” environments .
Theoretical models imply that these results may be due to the presence of more actively growing and/or massive SMBHs in LBGs and LAEs within the protocluster compared to the field .
Such a result is expected in a scenario where enhanced merger activity in the protocluster drives accelerated galaxy and SMBH growth at z \lower 2.15 pt \hbox { $ \buildrel > \over { \sim } $ } 2–3 .
Using Spitzer IRAC imaging we found that the fraction of IRAC detected LBGs is significantly larger in the protocluster than in the field ( by a factor of 3.0 ^ { +2.0 } _ { -1.3 } ) .
From these data , we constrained the median rest-frame H -band luminosity in the protocluster to be \buildrel > \over { \sim } 1.2–1.8 times larger than that for the field .
When combined with our X-ray data , this suggests that both galaxies and SMBHs grew more rapidly in protocluster environments .