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A dwarf galaxy near the sight line to PKS 0454+0356 - A fading 'faint blue galaxy'?We report the discovery of a dwarf galaxy (MB = -17.2 for H0 = 50 km/s per Mpc) at z = 0.072 which is only 4 arcsec (3.7/h(100) kpc) in projection from the line of sight to the bright quasar PKS 0454+0356 (z(em) = 1.345). The dwarf has very blue optical and optical/IR colors and exhibits line emission indicative of ongoing or recent star formation. However, there is no detection of Ca II 3934 A, 3969 A absorption at z(abs) = 0.072 to equivalent width limits (3 sigma) of about 40 mA, which would suggest an H I column density along the line of sight of less than 5 x 10 exp 19/sq cm, if the Ca II/H I ratio is similar to sight lines in the Galaxy. Based on the absence of Ca II absorption and the unusually weak line emission given the very blue color of the dwarf, we speculate that it may be close to exhausting its supply of gas. As its star formation rate declines, the galaxy's blue magnitude should fade substantially, eventually reaching a quiescent state in accord with its K luminosity of about 0.005 L*. Future observations of the sight line to PKS 0454+0356 using HST in search of Mg II resonance lines, or a search for 21 cm absorption against the quasar radio continuum, could place even more stringent limits on the extent of the gas associated with an intrinsically faint, star-forming dwarf.
Document ID
19930071095
Acquisition Source
Legacy CDMS
Document Type
Reprint (Version printed in journal)
External Source(s)
Authors
Steidel, Charles C.
(NASA Headquarters Washington, DC United States)
Dickinson, Mark
(California Univ. Berkeley, United States)
Bowen, David V.
(Space Telescope Science Inst. Baltimore, MD, United States)
Date Acquired
August 16, 2013
Publication Date
August 20, 1993
Publication Information
Publication: Astrophysical Journal, Part 2 - Letters
Volume: 413
Issue: 2
ISSN: 0004-637X
Subject Category
Astrophysics
Accession Number
93A55092
Funding Number(s)
CONTRACT_GRANT: NAS5-26555
Distribution Limits
Public
Copyright
Other

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