HUBBLE SPACE TELESCOPE WFC3 GRISM SPECTROSCOPY AND IMAGING OF A GROWING COMPACT GALAXY AT z = 1.9

Journal Article · Sun Aug 01 04:00:00 EDT 2010 · Astrophysical Journal Letters

DOI:https://doi.org/10.1088/2041-8205/718/2/L73· OSTI ID:21451023

Van Dokkum, Pieter G; Brammer, Gabriel ^[1]

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1. Department of Astronomy, Yale University, New Haven, CT 06520-8101 (United States)

We present HST/WFC3 grism near-IR spectroscopy of the brightest galaxy at z > 1.5 in the GOODS-South WFC3 ERS grism pointing. The spectrum is of remarkable quality and shows the redshifted Balmer lines H{beta}, H{gamma}, and H{delta} in absorption at z = 1.902 {+-} 0.002. The absorption lines can be produced by a post-starburst stellar population with a luminosity-weighted age of {approx}0.5 Gyr. The mass-to-light ratio inferred from the spectrum implies a stellar mass of (4 {+-} 1) x 10{sup 11} M{sub sun}. We determine the morphology of the galaxy from a deep WFC3 H{sub 160} image. Similar to other massive galaxies at z {approx} 2 the galaxy is compact, with an effective radius of 2.1 {+-} 0.3 kpc. Although most of the light is in a compact core, the galaxy has two red, smooth spiral arms that appear to be tidally induced. The spatially resolved spectroscopy demonstrates that the center of the galaxy is quiescent whereas the surrounding disk is forming stars, as it shows H{beta} in emission. The galaxy interacts with a companion at a projected distance of 18 kpc, which also shows prominent tidal features. The companion is a factor of {approx}10 fainter than the primary galaxy and may have a lower metallicity. It is tempting to interpret these observations as evidence for the growth of compact, quiescent high-redshift galaxies through minor mergers, which has been proposed by several recent observational and theoretical studies. Interestingly both objects host luminous active galactic nuclei, which implies that these mergers can be accompanied by significant black hole growth.

• OSTI ID: 21451023
• Journal Information: Astrophysical Journal Letters, Journal Name: Astrophysical Journal Letters Journal Issue: 2 Vol. 718; ISSN 2041-8205
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTRONOMY AND ASTROPHYSICS
ABSORPTION
BALMER LINES
BLACK HOLES
COSMOLOGY
EVOLUTION
GALACTIC EVOLUTION
GALAXIES
GALAXY NUCLEI
INFRARED SPECTRA
LUMINOSITY
MORPHOLOGY
OPTICAL PROPERTIES
PHYSICAL PROPERTIES
RED SHIFT
SORPTION
SPECTRA
SPECTROSCOPY
STARS
TELESCOPES