Browsing by Author "Barger, A. J."

Now showing 1 - 5 of 5
  • No Thumbnail Available
    Item
    2 mm Observations and the Search for High-redshift Dusty Star-forming Galaxies
    (2023) Cowie, L. L.; Barger, A. J.; Bauer, F. E.
    Finding high-redshift ( z >> 4) dusty star-forming galaxies is extremely challenging. It has recently been suggested that millimeter selections may be the best approach since the negative K-correction makes galaxies at a given farinfrared luminosity brighter at z greater than or similar to 4 than those at z = 2-3. Here we analyze this issue using a deep Atacama Large Millimeter/submillimeter Array (ALMA) 2 mm sample obtained by targeting ALMA 870 mu m priors (these priors were the result of targeting SCUBA-2 850 mu m sources) in the GOODS-S. We construct prior-based 2 mm galaxy number counts and compare them with published blank field-based 2 mm counts, finding good agreement down to 0.2 mJy. Only a fraction of the current 2 mm extragalactic background light is resolved, and we estimate what observational depths may be needed to resolve it fully. By complementing the 2 mm ALMA data with a deep SCUBA-2 450 mu m sample, we exploit the steep gradient with a redshift of the 2 mm-450 mu m flux density ratio to estimate redshifts for those galaxies without spectroscopic or robust optical/near-infrared photometric redshifts. Our observations measure galaxies with star formation rates in excess of 250M(circle dot) yr(-1). For these galaxies, the star formation rate densities fall by a factor of 9 from z = 2-3 to z = 5-6.
  • Thumbnail Image
    Item
    A Submillimeter Perspective on the GOODS Fields (SUPER GOODS). III. A Large Sample of ALMA Sources in the GOODS-S
    (2018) Cowie, L. L.; Gonzalez-Lopez, J.; Barger, A. J.; Bauer, Franz Erik; Hsu, L. -Y.; Wang, W. -H.
  • No Thumbnail Available
    Item
    A Submillimeter Survey of Faint Galaxies behind 10 Strong Lensing Clusters
    (2022) Cowie, L. L.; Barger, A. J.; Bauer, F. E.; Chen, C-C; Jones, L. H.; Orquera-Rojas, C.; Rosenthal, M. J.; Taylor, A. J.
    We present deep SCUBA-2 450 mu m and 850 mu m imaging of 10 strong lensing clusters. We provide a >4 sigma SCUBA-2 850 mu m catalog of the 404 sources lying within a radius of 4.' 5 4.5 sigma Atacama Large Millimeter/submillimeter Array (ALMA) 850 mu m detections in the clusters A370, MACSJ1149.5+2223, and MACSJ0717.5+3745 from our targeted ALMA observations, along with catalogs of all other >4.5 sigma ALMA (mostly 1.2 mm) detections in any of our cluster fields from archival ALMA observations. For the ALMA detections, we give spectroscopic or photometric redshifts, where available, from our own Keck observations or from the literature. We confirm the use of the 450-850 mu m flux ratio for estimating redshifts. We use lens models to determine magnifications, most of which are in the 1.5-4 range. After supplementing the ALMA cluster sample with Chandra Deep Field ALMA and Submillimeter Array samples, we find no evidence for evolution in the redshift distribution of submillimeter galaxies down to demagnified 850 mu m fluxes of 0.5 mJy. Given this result, we conclude that our observed trend of increasing F160W to 850 mu m flux ratio from brighter to fainter demagnified 850 mu m flux results from the fainter submillimeter galaxies having less extinction. However, there is wide spread in this relation, including the presence of some optical/near-infrared dark galaxies down to fluxes below 1 mJy. Finally, with insights from our ALMA analysis, we analyze our SCUBA-2 sample and present 55 850 mu m bright z > 4 candidates.
  • No Thumbnail Available
    Item
    Dust Properties of 870 μm-selected Galaxies in GOODS-S
    (2023) McKay, S. J.; Barger, A. J.; Cowie, L. L.; Bauer, F. E.; Rosenthal, M. J. Nicandro
    We analyze the dust properties of 57 870 mu m-selected dusty star-forming galaxies in GOODS-S using new deep Atacama Large Millimeter/Submillimeter Array 1.2, 2, and 3 mm continuum imaging together with other farinfrared through millimeter data. We fit the spectral energy distributions (SEDs) with optically thin modified blackbodies to constrain the emissivity indices and effective dust temperatures, finding a median emissivity index of beta=1.78(-0.25)(+0.43) and a median temperature of T-d =33.6(-5.4)(+12.1) K. We observe a negative correlation between beta and T-d. By testing several SED models, we determine that the derived emissivity indices can be influenced by opacity assumptions. Our temperature measurements are consistent with no evolution in dust temperature with redshift.
  • Thumbnail Image
    Item
    On the Absence of High-redshift AGNs : Little Growth in the Supermassive Black Hole Population at High Redshifts
    (2020) Cowie, L. L.; Barger, A. J.; Bauer, Franz Erik; Gozález López, José Ignacio