The Chandra Deep Field North Survey. XIV. X-Ray-detected Obscured AGNs and Starburst Galaxies in the Bright Submillimeter Source Population

By D. Alexander, F. E. Bauer, W. N. Brandt, A. Hornschemeier, C. Vignali, G. Garmire, D. Schneider, G. Chartas, S. C. Gallagher. 2002

151 citations recorded by the source corpus.

We provide X-ray constraints and perform the first X-ray spectral analyses for bright SCUBA sources (f850 μm ≥ 5 mJy; signal-to-noise ratio ≥4) in an 8.′4 × 8.′4 area of the 2 Ms Chandra Deep Field North survey containing the Hubble Deep Field North. X-ray emission is detected from seven of the 10 bright submillimeter sources in this region down to 0.5–8.0 keV fluxes of ≈1 × 10-16 ergs cm-2 s-1, corresponding to an X-ray–detected submillimeter source density of 360 deg-2; our analyses suggest that this equates to an X-ray–detected fraction of the bright submillimeter source population of ≳36%, although systematic effects may be present. Two of the X-ray–detected sources have nearby (within 3″) X-ray companions, suggesting merging/interacting sources or gravitational lensing effects, and three of the X-ray–detected sources lie within the approximate extent of the protocluster candidate CXOHDFN J123620.0+621554. Five of the X-ray–detected sources have flat effective X-ray spectral slopes (Γ < 1.0), suggesting obscured AGN activity. X-ray spectral analyses suggest that one of these AGNs may be a Compton-thick source; of the other four AGNs, three appear to be Compton-thin sources and one has poor constraints. The rest-frame unabsorbed X-ray luminosities of these AGNs are more consistent with those of Seyfert galaxies than QSOs (i.e., LX ≈ 1043–1044 ergs s-1). Thus, the low X-ray detection rate of bright submillimeter sources by moderately deep X-ray surveys appears to be due to the relatively low luminosities of the AGNs in these sources rather than Compton-thick absorption. A comparison of these sources with the well-studied, heavily obscured AGN NGC 6240 shows that the average AGN contribution is negligible at submillimeter wavelengths. The X-ray properties of the other two X-ray–detected sources are consistent with those expected from luminous star formation; however, we cannot rule out the possibility that low-luminosity AGNs are present. The three X-ray–undetected sources appear to lie at high redshift (z > 4) and could be either AGNs or starburst galaxies.

Subfields: Astronomy and Astrophysics, Nuclear and High Energy Physics

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In Astronomy and Astrophysics

1. D. M. Alexander
2. P. Hopkins
3. L. Hernquist
4. R. Dav'e
5. E. Daddi
6. D. Narayanan
7. R. Somerville
8. Mark Dickinson

In Nuclear and High Energy Physics

1. D. M. Alexander
2. W. N. Brandt
3. R. Ivison
4. I. Smail
5. G. Hasinger
6. A. Blain
7. S. Chapman
8. F. Walter

Citations in the corpus

• Astrophysical and cosmological information from large-scale submillimetre surveys of extragalactic sources (2007, background): “Alexander et al. (2003, 2005) have found that a substantial fraction of sub-mm bright galaxies harbor an active galactic nucleus (AGN).”
• The deepest Herschel-PACS far-infrared survey: number counts and infrared luminosity functions from combined PEP/GOODS-H observations (2013, methodology): “The extensive observations of the GOODS fields made by the PEP and GOODS-H surveys is explained by the availability of a deep multi-wavelength database including X-ray (Alexander et al. 2003; Xue et al. 2011), optical (Giavalisco et al. 2004), near-infrared (CANDELS; Grogin et al. 2011), mid-infrare”
• A survey of molecular gas in luminous sub-millimetre galaxies (2012, methodology): “We derive SMBH masses from the X-ray luminosity integrated from 0.5 to 8 keV (Alexander et al. 2003), assuming that the X-ray emission from the AGN accounts for 6+12−4 per cent of its total bolometric luminosity (Elvis et al. 1994).”
• EVIDENCE FOR A CLUMPY, ROTATING GAS DISK IN A SUBMILLIMETER GALAXY AT z = 4 (2012, background): “Their huge far– infrared (FIR) luminosities (∼1013 L⊙) are believed to be primarily driven by intense (∼103M⊙ yr−1) star formation (e.g., Alexander et al. 2005, 2003), adding to their already significant stellar masses (e.g., Borys et al. 2005; Hainline et al. 2011).”
• Evolution of the dusty infrared luminosity function from z = 0 to z = 2.3 using observations from Spitzer (2011, methodology): “In GOODS-N, optical observations in theBVIz passbands were obtained with the Advanced Camera for Surveys(ACS) onboard theHubble Space telescope(HST) as part of the GOODS ACS Treasury program (M. Giavalisco and the GOODS Team, 2010, in preparation) while near infrared observations in theJK passbands ”
• The evolution of the dust temperatures of galaxies in the SFR–M∗ plane up to z ~ 2 (2013, methodology): “We complemented this multiwavelength catalogue with the X-ray Chandra 2-Ms catalogue of Alexander et al. (2003).”
• DEEP EXTRAGALACTIC X-RAY SURVEYS (2005, methodology): “Even the deepest Chandra observations performed to date do not suffer from significant source confusion (Alexander et al. 2003b), in contrast to the case for XMM-Newton, where confusion becomes significant for >∼ 100–200 ks exposures.”
• Enhanced star formation rates in AGN hosts with respect to inactive galaxies from PEP-Herschel observations (2012, methodology): “For GOODS-N we used the 2 Msec Chandra Deep FieldNorth catalogue of Alexander et al. (2003) and an updated ver- sion of the classification into AGNs and other types of X-ray sources compiled by Bauer et al. (2004) (see also Shao et al. 2010).”
• Testing the evolutionary link between submillimetre galaxies and quasars: CO observations of QSOs at z∼ 2 (2008, methodology): “This position corresponds to within 0.5 arcsec of an I = 24.7 counterpart (Smail et al. 2004) with a radio flux of ≤ 15µ Jy (Biggs & Ivison 2006) which is also undetected in the Chandra observations (Alexander et al. 2003).”
• Radiative feedback from quasars and the growth of massive black holes in stellar spheroids (2004, background): “…forming galaxies at redshift z ∼ 3, including Lyman Break Galaxies and bright submillimeter SCUBA galaxies, generally exhibit only moderate active galactic nucleus (AGN) activity (Steidel et al. 2002; Alexander et al. 2003; Lehmer et al. 2004), indicating that their central MBHs are still growing.”
• On the Maximum Luminosity of Galaxies and Their Central Black Holes: Feedback from Momentum-driven Winds (2004, background): “Second, although some rapidly star-forming SCUBA sources at highz are inferred to host quasars, in many cases there is X-ray evidence for more modest AGN withL∼ 1043−1044 ergs s−1 (e.g., Alexander et al. 2003).”
• What drives the growth of black holes (2011, background): “For example, the deepest X-ray surveys (the Chandra Deep Fields; CDFs; Brandt et al. 2001; Giacconi et al. 2002; Alexander et al. 2003b; Luo et al. 2008; Xue et al. 2011) can detect low-luminosity AGNs similar to NGC 4051 (see Fig.”
• The X-Ray Spectral Properties of SCUBA Galaxies (2005, methodology): “Given the low surface density of SMGs, we also searched for X-ray counterparts, using the complete supplementary Chandra catalog of Alexander et al. (2003a), and found one further match; the probability of this match being spurious is <1% (see x 2.4 of Alexander et al. 2003b).”
• Multiwavelength Study of Massive Galaxies at z ~ 2. II. Widespread Compton-thick Active Galactic Nuclei and the Concurrent Growth of Black Holes and Bulges (2007, background): “…factor of∼ 2 higher than that of X-ray sources individually detected in X-rays in GOODS-S (Zheng et al 2004), a factor≈ 10 higher than X-ray detected submillimeter-emitting galaxies (Alexander et al. 2003b), and ≈ 20 times higher than X-ray undetected power-law AGN candidates (Donley et al. 2007).”
• A remarkably flat relationship between the average star formation rate and AGN luminosity for distant X-ray AGN. (2015, methodology): “Restframe, hard-band 2–8 keV luminosities were calculated following Alexander et al. (2003a) with the equation, L2−8 keV= 4π × D2L × F2−8keV × (1 + z)( −2), (1) where F2−8 keV is the observed X-ray hard-band flux (2–8 keV), DL is the luminosity distance, z is the redshift (see Section 2.3), and is…”
• THE STELLAR MASS CONTENT OF SUBMILLIMETER-SELECTED GALAXIES (2010, background): “…and mid-IR spectra of SMGs indicate that the majority of the population are not dominated by an active nucleus (AGN), many SMGs host AGN activity (Alexander et al. 2003, 2005; Pope et al. 2008; Menéndez-Delmestre et al. 2009), which may not be negligible for the purpose of stellar mass studies.”
• The Rest-Frame Optical Spectra of SCUBA Galaxies (2004, methodology): “64 and star formation could contribute to their immense farinfrared luminosities, and without further information it is impossible to disentangle the precise energy source (Alexander et al. 2003a).”
• The 0.4 < z < 1.3 star formation history of the Universe as viewed in the far-infrared (2009, methodology): “In order to test the presence of AGNs in the GOODS field, we used the deepestChandraX-ray observations i.e the 1Ms maps for the CDF-S and the 2 Ms maps for the CDF-N (Alexander et al. 2003).”