Browsing by Author "Finkelstein, Steven L."

Now showing 1 - 5 of 5
  • Thumbnail Image
    Item
    Characterization of Two 2 mm detected Optically Obscured Dusty Star-forming Galaxies
    (2022) Manning, Sinclaire M.; Casey, Caitlin M.; Zavala, Jorge A.; Magdis, Georgios E.; Drew, Patrick M.; Champagne, Jaclyn B.; Aravena, Manuel; Béthermin, Matthieu; Clements, David L.; Finkelstein, Steven L.; Fujimoto, Seiji; Hayward, Christopher C.; Hodge, Jacqueline A.; Ilbert, Olivier; Kartaltepe, Jeyhan S.; Knudsen, Kirsten K.; Koekemoer, Anton M.; Man, Allison W. S.; Sanders, David B.; Sheth, Kartik; Spilker, Justin S.; Staguhn, Johannes; Talia, Margherita; Treister, Ezequiel; Yun, Min S.
    The 2 mm Mapping Obscuration to Reionization with ALMA (MORA) Survey was designed to detect high-redshift (z greater than or similar to 4), massive, dusty star-forming galaxies (DSFGs). Here we present two likely high-redshift sources, identified in the survey, whose physical characteristics are consistent with a class of optical/near-infrared (OIR)-invisible DSFGs found elsewhere in the literature. We first perform a rigorous analysis of all available photometric data to fit spectral energy distributions and estimate redshifts before deriving physical properties based on our findings. Our results suggest the two galaxies, called MORA-5 and MORA-9, represent two extremes of the "OIR-dark" class of DSFGs. MORA-5 (z(phot) = 4.3(-1.3)(+1.5)) is a significantly more active starburst with a star formation rate (SFR) of 830(-190)(+340) M-circle dot yr(-1) compared to MORA-9 (z(phot) = 4.3(-1.0)(+1.3)), whose SFR is a modest 200(-60)(+250) M-circle dot yr(-1). Based on the stellar masses (M-star approximate to 10(10-11) M-circle dot), space density (n similar to (5 +/- 2) x 10(-6) Mpc(-3), which incorporates two other spectroscopically confirmed OIR-dark DSFGs in the MORA sample at z = 4.6 and z = 5.9), and gas depletion timescales (<1 Gyr) of these sources, we find evidence supporting the theory that OIR-dark DSFGs are the progenitors of recently discovered 3 < z < 4 massive quiescent galaxies.
  • Thumbnail Image
    Item
    Ly alpha EMITTER GALAXIES AT z similar to 2.8 IN THE EXTENDED CHANDRA DEEP FIELD SOUTH. I. TRACING THE LARGE-SCALE STRUCTURE VIA Ly alpha IMAGING
    (IOP PUBLISHING LTD, 2016) Zheng, Zhen Ya; Malhotra, Sangeeta; Rhoads, James E.; Finkelstein, Steven L.; Wang, Jun Xian; Jiang, Chun Yan; Cai, Zheng
    We present a narrowband survey with three adjacent filters for z - 2.8-2.9 Lyman alpha (Ly alpha) emitter (LAE) galaxies in the Extended Chandra Deep Field South (ECDFS), along with spectroscopic follow-up. With a complete sample of 96 LAE candidates in the narrowband NB466, we confirm the large-scale structure at z similar to 2.8 suggested by previous spectroscopic surveys. Compared to the blank field detected with the other two narrowband filters NB470 and NB475, the LAE-density excess in NB466 (900 arcmin(2)) is similar to 6.0 +/- 0.8 times the standard deviation expected at z similar to 2.8, assuming a linear bias of 2. The overdense large-scale structure in NB466 can be decomposed into four protoclusters, whose overdensities (each within an equivalent comoving volume 15(3) Mpc(3)) relative to the blank field (NB470+NB475) are in the range of 4.6-6.6. These four protoclusters are expected to evolve into a Coma-like cluster (M >= 10(15) M-circle dot) at z similar to 0. We also investigate the various properties of LAEs at z = 2.8-2.9 and their dependence on the environment. The average star formation rates derived from the Lya, rest-frame UV, and X-ray bands are similar to 4, 10, and < 16 M-circle dot yr(-1), respectively, implying a Ly alpha escape fraction of 25% less than or similar to f(ESC)(Ly alpha) less than or similar to 40% and a UV continuum escape fraction of f(ESC)(UV,cont) greater than or similar to 62% for LAEs at z similar to 2.8. The Ly alpha photon density calculated from the integrated Ly alpha luminosity function in the overdense field (NB466) is similar to 50% higher than that in the blank field (NB470+NB475), and more bright LAEs are found in the overdense field. The three brightest LAEs, including a quasar at z = 2.81, are all detected in the X-ray band and in NB466. These three LAE-active galactic nuclei contribute an extra 20%-30% Lya photon density compared to other LAE galaxies. Furthermore, we find that LAEs in overdense regions have larger equivalent width values, bluer U-B and V-R (similar to 2-3 sigma) colors compared with those in lower density regions, indicating that LAEs in overdense regions are younger and possible less dusty. We conclude that the structure at z similar to 2.8 in the ECDFS field is a very significant and rare density peak similar to the SSA22 protocluster, and narrowband imaging is an efficient method of detecting and studying such structures in the high-z universe.
  • Thumbnail Image
    Item
    Mapping Obscuration to Reionization with ALMA (MORA): 2 mm Efficiently Selects the Highest-redshift Obscured Galaxies
    (2021) Casey, Caitlin M.; Zavala, Jorge A.; Manning, Sinclaire M.; Aravena, Manuel; Béthermin, Matthieu; Caputi, Karina I.; Champagne, Jaclyn B.; Clements, David L.; Drew, Patrick; Finkelstein, Steven L.; Fujimoto, Seiji; Hayward, Christopher C.; Dekel, Anton M.; Kokorev, Vasily; Lagos, Claudia del P.; Long, Arianna S.; Magdis, Georgios E.; Man, Allison W. S.; Mitsuhashi, Ikki; Popping, Gergö; Spilker, Justin; Staguhn, Johannes; Talia, Margherita; Toft, Sune; Treister, Ezequiel; Weaver, John R.; Yun, Min
    We present the characteristics of 2 mm selected sources from the largest Atacama Large Millimeter/submillimeter Array (ALMA) blank-field contiguous survey conducted to date, the Mapping Obscuration to Reionization with ALMA (MORA) survey covering 184 arcmin(2) at 2 mm. Twelve of 13 detections above 5 sigma are attributed to emission from galaxies, 11 of which are dominated by cold dust emission. These sources have a median redshift of < Z(2) (mm)> = 3.6(-0.3)(+0.4) primarily based on optical/near-infrared photometric redshifts with some spectroscopic redshifts, with 77% +/- 11% of sources at z > 3 and 38% +/- 12% of sources at z > 4. This implies that 2 mm selection is an efficient method for identifying the highest-redshift dusty star-forming galaxies (DSFGs). Lower-redshift DSFGs (z < 3) are far more numerous than those at z > 3 yet are likely to drop out at 2 mm. MORA shows that DSFGs with star formation rates in excess of 300 M-circle dot yr(-1) and a relative rarity of similar to 10(-5) Mpc(-3) contribute similar to 30% to the integrated star formation rate density at 3 < z < 6. The volume density of 2 mm selected DSFGs is consistent with predictions from some cosmological simulations and is similar to the volume density of their hypothesized descendants: massive, quiescent galaxies at z > 2. Analysis of MORA sources' spectral energy distributions hint at steeper empirically measured dust emissivity indices than reported in typical literature studies, with = 2.2(-0.4)(+0.5). The MORA survey represents an important step in taking census of obscured star formation in the universe's first few billion years, but larger area 2 mm surveys are needed to more fully characterize this rare population and push to the detection of the universe's first dusty galaxies.
  • Thumbnail Image
    Item
    TO STACK OR NOT TO STACK : SPECTRAL ENERGY DISTRIBUTION PROPERTIES OF Lyα-EMITTING GALAXIES AT z=2.1
    (2014) Vargas, Carlos J.; Bish, Hannah; Acquaviva, Viviana; Gawiser, Eric; Finkelstein, Steven L.; Ciardullo, Robin; Ashby, Matthew L. N.; Feldmeier, John; Ferguson, Henry; Padilla, Nelson; Gronwall, Caryl; Guaita, Lucía; Hagen, Alex; Koekemoer, Anton; Kurczynski, Peter; Newman, Jeffrey A.
  • No Thumbnail Available
    Item
    TO STACK OR NOT TO STACK: SPECTRAL ENERGY DISTRIBUTION PROPERTIES OF Lyα-EMITTING GALAXIES AT z=2.1
    (2014) Vargas, Carlos J.; Bish, Hannah; Acquaviva, Viviana; Gawiser, Eric; Finkelstein, Steven L.; Ciardullo, Robin; Ashby, Matthew L. N.; Feldmeier, John; Ferguson, Henry; Gronwall, Caryl; Guaita, Lucia; Hagen, Alex; Koekemoer, Anton; Kurczynski, Peter; Newman, Jeffrey A.; Padilla, Nelson
    We use the Cosmic Assembly Near-Infrared Deep Extragalactic Legacy Survey (CANDELS) GOODS-S multi-wavelength catalog to identify counterparts for 20 Ly alpha emitting (LAE) galaxies at z = 2.1. We build several types of stacked spectral energy distributions (SEDs) of these objects. We combine photometry to form average and median flux-stacked SEDs, and postage-stamp images to form average and median image-stacked SEDs. We also introduce scaled flux stacks that eliminate the influence of variation in overall brightness. We use the SED fitting code SpeedyMC to constrain the physical properties of individual objects and stacks. Our LAEs at z = 2.1 have stellar masses ranging from 2 x 10(7) M-circle dot to 8 x 10(9) M-circle dot (median = 3 x 10(8) M-circle dot), ages ranging from 4 Myr to 500 Myr (median = 100 Myr), and E(B - V) between 0.02 and 0.24 (median = 0.12). Although still low, this represents significantly more dust reddening than has been reported for LAEs at higher redshifts. We do not observe strong correlations between Ly alpha equivalent width (EW) and age or E(B - V). The Ly alpha radiative transfer (q) factors of our sample are predominantly close to one and do not correlate strongly with EW or E(B - V). The absence of strong correlations with EW or q implies that Ly alpha radiative transfer is highly anisotropic and/or prevents Ly alpha photons from scattering in dusty regions. The SED parameters of the flux stacks match the average and median values of the individual objects, with the flux-scaled median SED performing best with uncertainties reduced by a factor of two. Median image-stacked SEDs provide a poor representation of the median individual object, and none of the stacking methods capture the large dispersion of LAE properties.