skip to main content
OSTI.GOV title logo U.S. Department of Energy
Office of Scientific and Technical Information

Title: SUBMILLIMETER ARRAY IDENTIFICATION OF THE MILLIMETER-SELECTED GALAXY SSA22-AzTEC1: A PROTOQUASAR IN A PROTOCLUSTER?

Abstract

We present results from Submillimeter Array (SMA) 860 {mu}m subarcsecond astrometry and multiwavelength observations of the brightest millimeter (S{sub 1.1mm} = 8.4 mJy) source, SSA22-AzTEC1, found near the core of the SSA22 protocluster that is traced by Ly{alpha}-emitting galaxies at z = 3.09. We identify a 860 {mu}m counterpart with a flux density of S{sub 860{sub {mu}m}} = 12.2 {+-} 2.3 mJy and absolute positional accuracy that is better than 0.''3. At the SMA position, we find radio-to-mid-infrared counterparts, whilst no object is found in Subaru optical and near-infrared deep images at wavelengths {<=}1 {mu}m (J > 25.4 in AB, 2{sigma}). The photometric redshift estimate, using flux densities at {>=}24 {mu}m, indicates z{sub phot} = 3.19{sup +0.26}{sub -0.35}, consistent with the protocluster redshift. We then model the near-to-mid-infrared spectral energy distribution (SED) of SSA22-AzTEC1, and find that the SED modeling requires a large extinction (A{sub V} {approx} 3.4 mag) of starlight from a stellar component with M{sub star} {approx} 10{sup 10.9} M{sub sun}, assuming z = 3.1. Additionally, we find a significant X-ray counterpart with a very hard spectrum ({Gamma}{sub eff} = -0.34{sup +0.57}{sub -0.61}), strongly suggesting that SSA22-AzTEC1 harbors a luminous active galactic nuclei (AGNs; L{sub X} {approx} 3more » x 10{sup 44} erg s{sup -1}) behind a large hydrogen column (N{sub H} {approx} 10{sup 24} cm{sup -2}). The AGN, however, is responsible for only {approx}10% of the bolometric luminosity of the host galaxy, and therefore the star formation activity likely dominates the submillimeter emission. It is possible that SSA22-AzTEC1 is the first example of a protoquasar growing at the bottom of the gravitational potential underlying the SSA22 protocluster.« less

Authors:
; ; ;  [1]; ;  [2]; ; ;  [3]; ; ;  [4]; ; ;  [5]; ; ;  [6];  [7];  [8]
  1. Nobeyama Radio Observatory, National Astronomical Observatory of Japan, Nobeyama, Minamimaki, Minamisaku, Nagano 384-1305 (Japan)
  2. Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States)
  3. Astronomical Institute, Tohoku University, Aramaki, Aoba, Sendai, Miyagi 980-8578 (Japan)
  4. Institute of Astronomy, University of Tokyo, Osawa, Mitaka, Tokyo 181-0015 (Japan)
  5. Department of Physics, Durham University, Durham DH1 3LE (United Kingdom)
  6. National Astronomical Observatory of Japan, Osawa, Mitaka, Tokyo 181-8588 (Japan)
  7. Instituto Nacional de Astrofisica, Optica y Electronica, Aptdo. Postal 51 y 216, 72000 Puebla (Mexico)
  8. Department of Astronomy, University of Massachusetts, 710 North Pleasant Street, Amherst, MA 01003 (United States)
Publication Date:
OSTI Identifier:
21474495
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astrophysical Journal; Journal Volume: 724; Journal Issue: 2; Other Information: DOI: 10.1088/0004-637X/724/2/1270
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; BOLOMETERS; ENERGY SPECTRA; FLUX DENSITY; GALAXY NUCLEI; HYDROGEN; LUMINOSITY; QUASARS; RED SHIFT; SIMULATION; STARS; X-RAY GALAXIES; COSMIC RADIO SOURCES; COSMIC RAY SOURCES; COSMIC X-RAY SOURCES; ELEMENTS; GALAXIES; MEASURING INSTRUMENTS; NONMETALS; OPTICAL PROPERTIES; PHYSICAL PROPERTIES; SPECTRA

Citation Formats

Tamura, Y., Iono, D., Hatsukade, B., Kawabe, R., Wilner, D. J., Chung, A., Kajisawa, M., Hayashino, T., Ichikawa, T., Uchimoto, Y. K., Ikarashi, S., Kohno, K., Alexander, D. M., Lehmer, B. D., Matsuda, Y., Ezawa, H., Nakanishi, K., Takata, T., Hughes, D. H., and Wilson, G. W., E-mail: yoichi.tamura@nao.ac.j. SUBMILLIMETER ARRAY IDENTIFICATION OF THE MILLIMETER-SELECTED GALAXY SSA22-AzTEC1: A PROTOQUASAR IN A PROTOCLUSTER?. United States: N. p., 2010. Web. doi:10.1088/0004-637X/724/2/1270.
Tamura, Y., Iono, D., Hatsukade, B., Kawabe, R., Wilner, D. J., Chung, A., Kajisawa, M., Hayashino, T., Ichikawa, T., Uchimoto, Y. K., Ikarashi, S., Kohno, K., Alexander, D. M., Lehmer, B. D., Matsuda, Y., Ezawa, H., Nakanishi, K., Takata, T., Hughes, D. H., & Wilson, G. W., E-mail: yoichi.tamura@nao.ac.j. SUBMILLIMETER ARRAY IDENTIFICATION OF THE MILLIMETER-SELECTED GALAXY SSA22-AzTEC1: A PROTOQUASAR IN A PROTOCLUSTER?. United States. doi:10.1088/0004-637X/724/2/1270.
Tamura, Y., Iono, D., Hatsukade, B., Kawabe, R., Wilner, D. J., Chung, A., Kajisawa, M., Hayashino, T., Ichikawa, T., Uchimoto, Y. K., Ikarashi, S., Kohno, K., Alexander, D. M., Lehmer, B. D., Matsuda, Y., Ezawa, H., Nakanishi, K., Takata, T., Hughes, D. H., and Wilson, G. W., E-mail: yoichi.tamura@nao.ac.j. Wed . "SUBMILLIMETER ARRAY IDENTIFICATION OF THE MILLIMETER-SELECTED GALAXY SSA22-AzTEC1: A PROTOQUASAR IN A PROTOCLUSTER?". United States. doi:10.1088/0004-637X/724/2/1270.
@article{osti_21474495,
title = {SUBMILLIMETER ARRAY IDENTIFICATION OF THE MILLIMETER-SELECTED GALAXY SSA22-AzTEC1: A PROTOQUASAR IN A PROTOCLUSTER?},
author = {Tamura, Y. and Iono, D. and Hatsukade, B. and Kawabe, R. and Wilner, D. J. and Chung, A. and Kajisawa, M. and Hayashino, T. and Ichikawa, T. and Uchimoto, Y. K. and Ikarashi, S. and Kohno, K. and Alexander, D. M. and Lehmer, B. D. and Matsuda, Y. and Ezawa, H. and Nakanishi, K. and Takata, T. and Hughes, D. H. and Wilson, G. W., E-mail: yoichi.tamura@nao.ac.j},
abstractNote = {We present results from Submillimeter Array (SMA) 860 {mu}m subarcsecond astrometry and multiwavelength observations of the brightest millimeter (S{sub 1.1mm} = 8.4 mJy) source, SSA22-AzTEC1, found near the core of the SSA22 protocluster that is traced by Ly{alpha}-emitting galaxies at z = 3.09. We identify a 860 {mu}m counterpart with a flux density of S{sub 860{sub {mu}m}} = 12.2 {+-} 2.3 mJy and absolute positional accuracy that is better than 0.''3. At the SMA position, we find radio-to-mid-infrared counterparts, whilst no object is found in Subaru optical and near-infrared deep images at wavelengths {<=}1 {mu}m (J > 25.4 in AB, 2{sigma}). The photometric redshift estimate, using flux densities at {>=}24 {mu}m, indicates z{sub phot} = 3.19{sup +0.26}{sub -0.35}, consistent with the protocluster redshift. We then model the near-to-mid-infrared spectral energy distribution (SED) of SSA22-AzTEC1, and find that the SED modeling requires a large extinction (A{sub V} {approx} 3.4 mag) of starlight from a stellar component with M{sub star} {approx} 10{sup 10.9} M{sub sun}, assuming z = 3.1. Additionally, we find a significant X-ray counterpart with a very hard spectrum ({Gamma}{sub eff} = -0.34{sup +0.57}{sub -0.61}), strongly suggesting that SSA22-AzTEC1 harbors a luminous active galactic nuclei (AGNs; L{sub X} {approx} 3 x 10{sup 44} erg s{sup -1}) behind a large hydrogen column (N{sub H} {approx} 10{sup 24} cm{sup -2}). The AGN, however, is responsible for only {approx}10% of the bolometric luminosity of the host galaxy, and therefore the star formation activity likely dominates the submillimeter emission. It is possible that SSA22-AzTEC1 is the first example of a protoquasar growing at the bottom of the gravitational potential underlying the SSA22 protocluster.},
doi = {10.1088/0004-637X/724/2/1270},
journal = {Astrophysical Journal},
number = 2,
volume = 724,
place = {United States},
year = {Wed Dec 01 00:00:00 EST 2010},
month = {Wed Dec 01 00:00:00 EST 2010}
}
  • Strong gravitational lenses are now being routinely discovered in wide-field surveys at (sub-)millimeter wavelengths. We present Submillimeter Array (SMA) high-spatial resolution imaging and Gemini-South and Multiple Mirror Telescope optical spectroscopy of strong lens candidates discovered in the two widest extragalactic surveys conducted by the Herschel Space Observatory: the Herschel-Astrophysical Terahertz Large Area Survey (H-ATLAS) and the Herschel Multi-tiered Extragalactic Survey (HerMES). From a sample of 30 Herschel sources with S {sub 500} > 100 mJy, 21 are strongly lensed (i.e., multiply imaged), 4 are moderately lensed (i.e., singly imaged), and the remainder require additional data to determine their lensing status.more » We apply a visibility-plane lens modeling technique to the SMA data to recover information about the masses of the lenses as well as the intrinsic (i.e., unlensed) sizes (r {sub half}) and far-infrared luminosities (L {sub FIR}) of the lensed submillimeter galaxies (SMGs). The sample of lenses comprises primarily isolated massive galaxies, but includes some groups and clusters as well. Several of the lenses are located at z {sub lens} > 0.7, a redshift regime that is inaccessible to lens searches based on Sloan Digital Sky Survey spectroscopy. The lensed SMGs are amplified by factors that are significantly below statistical model predictions given the 500 μm flux densities of our sample. We speculate that this may reflect a deficiency in our understanding of the intrinsic sizes and luminosities of the brightest SMGs. The lensed SMGs span nearly one decade in L {sub FIR} (median L {sub FIR} = 7.9 × 10{sup 12} L {sub ☉}) and two decades in FIR luminosity surface density (median Σ{sub FIR} = 6.0 × 10{sup 11} L {sub ☉} kpc{sup –2}). The strong lenses in this sample and others identified via (sub-)mm surveys will provide a wealth of information regarding the astrophysics of galaxy formation and evolution over a wide range in redshift.« less
  • We study the properties of K-band-selected galaxies (K {sub AB} < 24) in the z = 3.09 SSA22 protocluster field. 430 galaxies at 2.6 < z {sub phot} < 3.6 are selected as potential protocluster members in a 112 arcmin{sup 2} area based on their photometric redshifts. We find that ≈20% of the massive galaxies with stellar masses >10{sup 11} M {sub ☉} at z {sub phot} ∼ 3.1 have colors consistent with those of quiescent galaxies with ages >0.5 Gyr. This fraction increases to ≈50% after correcting for unrelated foreground/background objects. We also find that 30% of the massivemore » galaxies are heavily reddened, dusty, star-forming galaxies. Few such quiescent galaxies at similar redshifts are seen in typical survey fields. An excess surface density of 24 μm sources at z {sub phot} ∼ 3.1 is also observed, implying the presence of dusty star-formation activity in the protocluster. Cross-correlation with the X-ray data indicates that the fraction of K-band-selected protocluster galaxies hosting active galactic nuclei (AGNs) is also high compared with the field. The sky distribution of the quiescent galaxies, the 24 μm sources, and the X-ray AGNs show clustering around a density peak of z = 3.1 Lyα emitters. A significant fraction of the massive galaxies have already become quiescent, while dusty star-formation is still active in the SSA22 protocluster. These findings indicate that we are witnessing the formation epoch of massive early-type galaxies in the centers of the predecessors to present-day rich galaxy clusters.« less
  • We report the results of 1.′5 × 3′ mapping at 1.1 mm with the Atacama Large Millimeter/submillimeter Array toward the central region of the z = 3.09 SSA22 protocluster. By combining our source catalog with archival spectroscopic redshifts, we find that eight submillimeter galaxies (SMGs) with flux densities, S{sub 1.1} {sub mm} = 0.7–6.4 mJy (L{sub IR} ∼ 10{sup 12.1}–10{sup 13.1} L{sub ⊙}) are at z = 3.08–3.10. Not only are these SMGs members of the protocluster, but they in fact reside within the node at the junction of the 50 Mpc scale filamentary three-dimensional structure traced by Lyα emitters in this field. The eight SMGs account formore » a star formation rate density (SFRD) ∼10 M{sub ⊙} yr{sup −1} Mpc{sup −3} in the node, which is two orders of magnitudes higher than the global SFRD at this redshift. We find that four of the eight SMGs host an X-ray-luminous active galactic nucleus. Our results suggest that the vigorous star formation activity and the growth of supermassive black holes (SMBHs) occurred simultaneously in the densest regions at z ∼ 3, which may correspond to the most active historical phase of the massive galaxy population found in the core of the clusters in the present universe. Two SMGs are associated with Lyα blobs, implying that the two populations coexist in high-density environments for a few cases.« less
  • We present the results of a densely sampled spectroscopic survey of the SSA22 protocluster at z ≈ 3.09. Our sample with Keck/LRIS spectroscopy includes 106 Ly α emitters (LAEs) and 40 Lyman break galaxies (LBGs) at z = 3.05–3.12. These galaxies are contained within the 9′ × 9′ region in which the protocluster was discovered, which also hosts the maximum galaxy overdensity in the SSA22 region. The redshift histogram of our spectroscopic sample reveals two distinct peaks, at z = 3.069 (blue; 43 galaxies) and z = 3.095 (red; 103 galaxies). Furthermore, objects in the blue and red peaks aremore » segregated on the sky, with galaxies in the blue peak concentrating toward the western half of the field. These results suggest that the blue and red redshift peaks represent two distinct structures in physical space. Although the double-peaked redshift histogram is traced in the same manner by LBGs and LAEs, and brighter and fainter galaxies, we find that 9 out of 10 X-ray AGNs in SSA22, and all 7 spectroscopically confirmed giant Ly α “blobs,” reside in the red peak. We combine our data set with sparsely sampled spectroscopy from the literature over a significantly wider area, finding preliminary evidence that the double-peaked structure in redshift space extends beyond the region of our dense spectroscopic sampling. In order to fully characterize the three-dimensional structure, dynamics, and evolution of large-scale structure in the SSA22 overdensity, we require the measurement of large samples of LAE and LBG redshifts over a significantly wider area, as well as detailed comparisons with cosmological simulations of massive cluster formation.« less
  • We present a sky simulation of the atomic H I-emission line and the first 10 {sup 12}C{sup 16}O rotational emission lines of molecular gas in galaxies beyond the Milky Way. The simulated sky field has a comoving diameter of 500 h {sup -1} Mpc; hence, the actual field of view depends on the (user-defined) maximal redshift z {sub max}; e.g., for z {sub max} = 10, the field of view yields approx4 x 4 deg{sup 2}. For all galaxies, we estimate the line fluxes, line profiles, and angular sizes of the H I and CO-emission lines. The galaxy sample ismore » complete for galaxies with cold hydrogen masses above 10{sup 8} M {sub sun}. This sky simulation builds on a semi-analytic model of the cosmic evolution of galaxies in a LAMBDA cold dark matter (LAMBDACDM) cosmology. The evolving CDM distribution was adopted from the Millennium Simulation, an N-body CDM simulation in a cubic box with a side length of 500 h {sup -1} Mpc. This side length limits the coherence scale of our sky simulation: it is long enough to allow the extraction of the baryon acoustic oscillations in the galaxy power spectrum, yet the position and amplitude of the first acoustic peak will be imperfectly defined. This sky simulation is a tangible aid to the design and operation of future telescopes, such as the Square Kilometre Array, Large Millimeter Telescope, and Atacama Large Millimeter/Submillimeter Array. The results presented in this paper have been restricted to a graphical representation of the simulated sky and fundamental dN/dz analyses for peak flux density limited and total flux limited surveys of H I and CO. A key prediction is that H I will be harder to detect at redshifts z approx> 2 than predicted by a no-evolution model. The future verification or falsification of this prediction will allow us to qualify the semi-analytic models.« less