DUST OBSCURATION AND METALLICITY AT HIGH REDSHIFT: NEW INFERENCES FROM UV, H{alpha}, AND 8 {mu}m OBSERVATIONS OF z {approx} 2 STAR-FORMING GALAXIES
- National Optical Astronomy Observatory, 950 N Cherry Ave., Tucson, AZ 85719 (United States)
- University of California at Santa Barbara, Santa Barbara, CA 93106 (United States)
- Institute of Astronomy, Madingley Road, Cambridge CB3 OHA (United Kingdom)
- California Institute of Technology, MS 105-24, Pasadena, CA 91125 (United States)
- University of California at Los Angeles, 430 Portola Plaza, Box 951547, Los Angeles, CA 90095 (United States)
We use a sample of 90 spectroscopically confirmed Lyman break galaxies with Halpha measurements and Spitzer MIPS 24 {mu}m observations to constrain the relationship between rest-frame 8 {mu}m luminosity (L{sub 8}) and star formation rate (SFR) for L* galaxies at z {approx} 2. We find a tight correlation with 0.24 dex scatter between L{sub 8} and H{alpha} luminosity/SFR for z {approx} 2 galaxies with 10{sup 10} L{sub sun} {approx}< L{sub IR} {approx}< 10{sup 12} L{sub sun}. Employing this relationship with a larger sample of 392 galaxies with spectroscopic redshifts, we find that the UV slope beta can be used to recover the dust attenuation of the vast majority of moderately luminous L* galaxies at z {approx} 2 to within a 0.4 dex scatter using the local correlation. Separately, young galaxies with ages {approx}<100 Myr appear to be less dusty than their UV slopes would imply based on the local trend and may follow an extinction curve that is steeper than what is typically assumed. Consequently, very young galaxies at high redshift may be significantly less dusty than inferred previously. Our results provide the first direct evidence, independent of the UV slope, for a correlation between UV and bolometric luminosity (L{sub bol}) at high redshift, in the sense that UV-faint galaxies are on average less infrared and less bolometrically luminous than their UV-bright counterparts. The L{sub bol}-L{sub UV} relation indicates that as the SFR increases, L{sub UV} turns over (or 'saturates') around the value of L* at z {approx} 2, implying that dust obscuration may be largely responsible for modulating the bright end of the UV luminosity function. Finally, dust attenuation is found to correlate with oxygen abundance at z {approx} 2. Accounting for systematic differences in local and high-redshift metallicity calibrations, we find that L* galaxies at z {approx} 2, while at least an order of magnitude more bolometrically luminous, exhibit ratios of metals to dust that are similar to those of local starbursts. This result is expected if high-redshift galaxies are forming their stars in a less metal-rich environment compared to local galaxies of the same luminosity, thus naturally leading to a redshift evolution in both the bolometric luminosity-metallicity and bolometric luminosity-obscuration relations.
- OSTI ID:
- 21394190
- Journal Information:
- Astrophysical Journal, Vol. 712, Issue 2; Other Information: DOI: 10.1088/0004-637X/712/2/1070; ISSN 0004-637X
- Country of Publication:
- United States
- Language:
- English
Similar Records
UV CONTINUUM SLOPE AND DUST OBSCURATION FROM z approx 6 TO z approx 2: THE STAR FORMATION RATE DENSITY AT HIGH REDSHIFT
MID-IR LUMINOSITIES AND UV/OPTICAL STAR FORMATION RATES AT z < 1.4