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Title: EXTENDED Ly{alpha} EMISSION FROM INTERACTING GALAXIES AT HIGH REDSHIFTS

Abstract

Recent observations have discovered a population of extended Ly{alpha} sources, dubbed Ly{alpha} blobs (LABs), at high redshift z {approx} 2-6.6. These LABs typically have a luminosity of L {approx} 10{sup 42}-10{sup 44} erg s{sup -1}, and a size of tens of kiloparsecs, with some giant ones reaching up to D {approx} 100 kpc. However, the origin of these LABs is not well understood. In this paper, we investigate a merger model for the formation of LABs by studying Ly{alpha} emission from interacting galaxies at high redshifts by means of a combination of hydrodynamics simulations with three-dimensional radiative transfer calculations. Our galaxy simulations focus on a set of binary major mergers of galaxies with a mass range of 3-7 Multiplication-Sign 10{sup 12} M{sub Sun} in the redshift range z {approx} 3-7, and we use the newly improved ART{sup 2} code to perform the radiative transfer calculations, which couple multi-wavelength continuum, ionization of hydrogen, and Ly{alpha} line emission. We find that intense star formation and enhanced cooling induced by gravitational interaction produce strong Ly{alpha} emission from these merging galaxies. The Ly{alpha} emission appears to be extended due to the extended distribution of sources and gas. During the close encounter of galaxy progenitorsmore » when the star formation rate peaks at {approx}10{sup 3} M{sub Sun} yr{sup -1}, our model produces LABs with luminosity of L {approx} 10{sup 42}-10{sup 44} erg s{sup -1}, and size of D {approx} 10-20 kpc at z > 6 and D {approx} 20-50 kpc at z {approx} 3, in broad agreement with observations in the same redshift range. Our results suggest that merging galaxies may produce some typical LABs as observed, but the giant ones may be produced by mergers more massive than those in our model, or a combination of mergers and cold accretion from filaments on a large scale.« less

Authors:
; ;  [1]
  1. Department of Astronomy and Astrophysics, Pennsylvania State University, 525 Davey Lab, University Park, PA 16802 (United States)
Publication Date:
OSTI Identifier:
22130972
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astrophysical Journal; Journal Volume: 773; Journal Issue: 2; Other Information: Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; COOLING; GALAXIES; GRAVITATIONAL INTERACTIONS; HYDRODYNAMIC MODEL; HYDROGEN; IONIZATION; LUMINOSITY; LYMAN LINES; RADIANT HEAT TRANSFER; RED SHIFT; STARS; THREE-DIMENSIONAL CALCULATIONS; WAVELENGTHS

Citation Formats

Yajima, Hidenobu, Li Yuexing, and Zhu Qirong, E-mail: yuh19@psu.edu. EXTENDED Ly{alpha} EMISSION FROM INTERACTING GALAXIES AT HIGH REDSHIFTS. United States: N. p., 2013. Web. doi:10.1088/0004-637X/773/2/151.
Yajima, Hidenobu, Li Yuexing, & Zhu Qirong, E-mail: yuh19@psu.edu. EXTENDED Ly{alpha} EMISSION FROM INTERACTING GALAXIES AT HIGH REDSHIFTS. United States. doi:10.1088/0004-637X/773/2/151.
Yajima, Hidenobu, Li Yuexing, and Zhu Qirong, E-mail: yuh19@psu.edu. Tue . "EXTENDED Ly{alpha} EMISSION FROM INTERACTING GALAXIES AT HIGH REDSHIFTS". United States. doi:10.1088/0004-637X/773/2/151.
@article{osti_22130972,
title = {EXTENDED Ly{alpha} EMISSION FROM INTERACTING GALAXIES AT HIGH REDSHIFTS},
author = {Yajima, Hidenobu and Li Yuexing and Zhu Qirong, E-mail: yuh19@psu.edu},
abstractNote = {Recent observations have discovered a population of extended Ly{alpha} sources, dubbed Ly{alpha} blobs (LABs), at high redshift z {approx} 2-6.6. These LABs typically have a luminosity of L {approx} 10{sup 42}-10{sup 44} erg s{sup -1}, and a size of tens of kiloparsecs, with some giant ones reaching up to D {approx} 100 kpc. However, the origin of these LABs is not well understood. In this paper, we investigate a merger model for the formation of LABs by studying Ly{alpha} emission from interacting galaxies at high redshifts by means of a combination of hydrodynamics simulations with three-dimensional radiative transfer calculations. Our galaxy simulations focus on a set of binary major mergers of galaxies with a mass range of 3-7 Multiplication-Sign 10{sup 12} M{sub Sun} in the redshift range z {approx} 3-7, and we use the newly improved ART{sup 2} code to perform the radiative transfer calculations, which couple multi-wavelength continuum, ionization of hydrogen, and Ly{alpha} line emission. We find that intense star formation and enhanced cooling induced by gravitational interaction produce strong Ly{alpha} emission from these merging galaxies. The Ly{alpha} emission appears to be extended due to the extended distribution of sources and gas. During the close encounter of galaxy progenitors when the star formation rate peaks at {approx}10{sup 3} M{sub Sun} yr{sup -1}, our model produces LABs with luminosity of L {approx} 10{sup 42}-10{sup 44} erg s{sup -1}, and size of D {approx} 10-20 kpc at z > 6 and D {approx} 20-50 kpc at z {approx} 3, in broad agreement with observations in the same redshift range. Our results suggest that merging galaxies may produce some typical LABs as observed, but the giant ones may be produced by mergers more massive than those in our model, or a combination of mergers and cold accretion from filaments on a large scale.},
doi = {10.1088/0004-637X/773/2/151},
journal = {Astrophysical Journal},
number = 2,
volume = 773,
place = {United States},
year = {Tue Aug 20 00:00:00 EDT 2013},
month = {Tue Aug 20 00:00:00 EDT 2013}
}
  • QSO absorption systems with damped Ly-alpha lines have been suggested as the high-redshift progenitors of present-day galaxies. As part of a survey of element abundances and star formation rates in these systems, long-slit, 1.5 A resolution spectroscopic observations of the z(em) = 2.67 QSO 0836 + 113 were obtained. The detection of a narrow emission line centered in the black core of the damped Ly-alpha absorption line at z(abs) = 2.465 is reported. It is suggested that the Ly-alpha is from star-forming H II regions associated with the z = 2.465 galaxy. The implications of the detection on future observationalmore » studies are discussed, emphasizing the need for low detector noise and high S/N for the sky background. 43 refs.« less
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  • We present the first spectroscopic measurements of the [O III] 5007 A line in two z {approx} 3.1 Ly{alpha} emitting galaxies (LAEs) using the new near-infrared instrument LUCIFER1 on the 8.4 m Large Binocular Telescope. We also describe the optical imaging and spectroscopic observations used to identify these LAEs. Using the [O III] line we have measured accurate systemic redshifts for these two galaxies, and discovered a velocity offset between the [O III] and Ly{alpha} lines in both, with the Ly{alpha} line peaking 342 and 125 km s{sup -1} redward of the systemic velocity. These velocity offsets imply that theremore » are powerful outflows in high-redshift LAEs. They also ease the transmission of Ly{alpha} photons through the interstellar medium and intergalactic medium around the galaxies. By measuring these offsets directly, we can refine both Ly{alpha}-based tests for reionization, and Ly{alpha} luminosity function measurements where the Ly{alpha} forest affects the blue wing of the line. Our work also provides the first direct constraints on the strength of the [O III] line in high-redshift LAEs. We find [O III] fluxes of 7 and 36 x10{sup -17} erg s{sup -1} cm{sup -2} in two z {approx} 3.1 LAEs. These lines are strong enough to dominate broadband flux measurements that include the line (in this case, K{sub s} -band photometry). Spectral energy distribution fits that do not account for the lines would therefore overestimate the 4000 A (and/or Balmer) break strength in such galaxies, and hence also the ages and stellar masses of such high-z galaxies.« less
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