Gas-Phase Metallicity Gradients at z~2

The broad spectral coverage and high angular resolution of GLASS are ideal for detailed studies of galaxies at intermediate redshifts. In Jones et al. 2015 our team analyzed the spatially resolved stellar mass and gas-phase metallicity in a system of three strongly lensed galaxies at redshift z=1.855, drawn from the first complete GLASS data set (MACS0717).

These initial GLASS data reveal strong, spatially extended emission lines in all three galaxies. We find no significant radial variation in metallicity, possibly as a result of gravitational interaction among the galaxies.

These results represent the first constraint of metallicity gradient evolution using HST. Our analysis also extends previous studies of the mass-metallicity relation to an order of magnitude lower stellar mass, confirming that GLASS is able to characterize dwarf galaxies at intermediate redshift. The mass-metallicity relation and metallicity gradient evolution are both valuable diagnostics of how gas cycles in and out of galaxies over cosmic time.

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GLASS Data Reveals The First Multiply Imaged Strongly Lensed SN

In GLASS data taken of the MACSJ1149.6+2223 cluster (z=0.54) in November, we discovered the first strongly lensed supernova visible in multiple images.  The supernova occurred in the spiral arm of a galaxy at redshift z=1.49 lensed by a foreground early-type cluster galaxy, whose gravitational potential forms four separate, strongly magnified images of the supernova.  With the Frontier Fields SN team, we describe the exciting system in Kelly et al. 2014.

Our team is measuring the time delays and relative magnifications between the separate images of the evolving supernova, by comparing the phase and brightness of the multiple light curves. These delays and magnifications will place tight constraints on the cosmic expansion rate, as well as the distribution of luminous and dark matter in the galaxy lens and the cluster.

The MACSJ1149.6+2223 galaxy cluster furthermore lenses the spiral host galaxy of the supernova itself into multiple images, and models of the cluster predict that the supernova will appear in the future at additional locations in the cluster field.

First paper released

Schmidt et al. (2014), ApJ 782:L36 

The first GLASS data arrived on 2013 December 24 and 30 and consists of 10029 and 3812 seconds of G102 and G141 spectroscopy on MACS0717, respectively, and comprise only ~1/20th of the final GLASS data product.

For the 9 redshift 6 galaxy candidates in MACS0717 with GLASS grism spectra clear of contamination we do not detect any emission lines down to a 1σ noise level of ∼5×10−18 erg s−1 cm−2. This confirms that the targeted high redshift candidates are not strong line emitters at lower redshift.

Furthermore, we spectroscopically confirm four multiply imaged strongly lensed systems by detecting emission lines ([OIII] and [OII])  the GLASS grism spectra, confirming the proposed photometric redshifts from the literature. 

For more details follow the link to ADS .