Lyman alpha and UV emission from star forming galaxies in the 3 Gyr Universe
by
Lucia Guaita
→
Europe/Stockholm
FA31
FA31
Description
Lyman alpha emitting (LAE) galaxies represent star forming galaxies at high-redshift in which the interstellar medium (ISM) gas and dust properties permit Lyman alpha photons to escape. In the context of MUSYC (Multi-wavelength Survey by Yale-Chile), we built a sample of ~200 z~2.1 LAEs in the Extended Chandra Deep Field South, selected to have Lyman alpha line rest-frame equivalent width, EW>20 A and flux, F_Lyalpha> 2 x 10^(-17) erg/sec/cm^2. At the same EW and Lyman alpha luminosity limit, a sample of ~150 z~3.1 LAEs was discovered in the same field. This allows us to make an unbiased comparison between the two redshifts. Most LAEs show photometric properties typical of blue galaxies with quite flat UV spectrum. At z~3.1 they appear to be dust-free galaxies in their first phases of star formation. At z~2.1 we also identify a red subsample, with properties different from the typical ones.
Spectral Energy Distribution analysis shows that z~2.1 LAEs are low-mass, moderately dusty galaxies, but the red subsample is composed by more massive and dustier galaxies, probably with favorable ISM conditions, such as galactic winds, that allow the Lyman alpha line to be present in their spectra despite the presence of dust. In addition to Lyman alpha, star formation and ISM properties can be investigated looking at the H alpha line, which is less sensitive to dust absorption. Line profiles in z~2 LAE spectra allow us to study how Lyman alpha and UV emission are regulated by intrinsic properties, such as gas density, dust amount, and ISM kinematics.
