LOW MASSES AND HIGH REDSHIFTS: THE EVOLUTION OF THE MASS-METALLICITY RELATION

• Published in: Astrophysical journal. Letters Vol. 776; no. 2
• Main Authors: Henry, Alaina, Straughn, Amber, Scarlata, Claudia, Bedregal, Alejandro G., Domínguez, Alberto, Siana, Brian, Masters, Daniel, Malkan, Matthew, Ross, Nathaniel, Martin, Crystal L., Atek, Hakim, Colbert, James W., Rafelski, Marc, Teplitz, Harry, Bunker, Andrew J., Dressler, Alan, Hathi, Nimish, McCarthy, Patrick
• Format: Journal Article
• Language: English
• Published: United States 20.10.2013
• Subjects: ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; CAMERAS; EVOLUTION; FEEDBACK; GALAXIES; MASS; RED SHIFT; SPACE; SPECTRA; SPECTROSCOPY; STARS; TELESCOPES; WIND
• ISSN: 2041-8205; 2041-8213
• DOI: 10.1088/2041-8205/776/2/L27

We present the first robust measurement of the high redshift mass-metallicity (MZ) relation at 10{sup 8} ∼< M/M {sub ☉} ∼< 10{sup 10}, obtained by stacking spectra of 83 emission-line galaxies with secure redshifts between 1.3 ∼< z ∼< 2.3. For these redshifts, infrared grism spectroscopy with the Hubble Space Telescope Wide Field Camera 3 is sensitive to the R {sub 23} metallicity diagnostic: ([O II] λλ3726, 3729 + [O III] λλ4959, 5007)/Hβ. Using spectra stacked in four mass quartiles, we find a MZ relation that declines significantly with decreasing mass, extending from 12+log(O/H) = 8.8 at M = 10{sup 9.8} M {sub ☉}, to 12+log(O/H) = 8.2 at M = 10{sup 8.2} M {sub ☉}. After correcting for systematic offsets between metallicity indicators, we compare our MZ relation to measurements from the stacked spectra of galaxies with M ∼> 10{sup 9.5} M {sub ☉} and z ∼ 2.3. Within the statistical uncertainties, our MZ relation agrees with the z ∼ 2.3 result, particularly since our somewhat higher metallicities (by around 0.1 dex) are qualitatively consistent with the lower mean redshift (z = 1.76) of our sample. For the masses probed by our data, the MZ relation shows a steep slope which is suggestive of feedback from energy-driven winds, and a cosmological downsizing evolution where high mass galaxies reach the local MZ relation at earlier times. In addition, we show that our sample falls on an extrapolation of the star-forming main sequence (the SFR-M {sub *} relation) at this redshift. This result indicates that grism emission-line selected samples do not have preferentially high star formation rates (SFRs). Finally, we report no evidence for evolution of the mass-metallicity-SFR plane; our stack-averaged measurements show excellent agreement with the local relation.