The Dependence of Star Formation Quenching and of Lyman Alpha Escape on Galaxy Structural Properties
Abstract
Galaxy structural properties such as size, morphology, and surface brightness bear the imprint of galaxies' evolutionary histories, and so are related with other properties such as stellar mass, star formation rate, and emergent spectra. We present two studies exploring such relationships. In the first, we investigate the relationships between 4000 Å break (D4000) strength, colors, stellar masses, and morphology in a sample of 352 galaxies at intermediate redshifts based on photometric and spectroscopic data from the Hubble Space Telescope. We identify quiescent galaxies in UVJ color space based on their D4000 strengths. Morphologically, most (66/68) of these newly identified quiescent galaxies have a prominent bulge component. However, not all of the bulge-dominated galaxies are quenched. Also, bulge-dominated galaxies are clearly separated into two main groups in the parameter space of specific star formation rate (sSFR) versus stellar mass and stellar surface density within the effective radius, while late-type disks and irregulars only show high sSFR. This suggests that the presence of a bulge is a necessary but not sufficient requirement for quenching at intermediate redshifts. In the second study, we investigate the UV star formation intensity (SFI, star formation rate per unit area) of 45 Green Pea galaxies to understand the Lyman-alpha (LyA) escape mechanisms and the associations with the SFI in LyA emitters. The SFI is measured by utilizing the COS/NUV images obtained from the Hubble Space Telescope. Our analysis shows that the SFI of Green Pea galaxies approximately ranges over an order of magnitude. Also, the ratio of SFI to galaxy stellar mass (SFI/Mstar) shows statistically significant positive correlations with the Spearman correlation coefficients of (p-values) ~0.5 (~4e-4) with LyA equivalent width and the LyA escape fraction. Since stellar mass correlates with gravitational potential, and SFI with the mechanisms driving galactic winds, the observed correlations would be consistent with a picture where outflow enables Lyman alpha escape. Therefore, our results emphasize the importance of galaxy structural properties in star formation quenching and LyA escape.
- Publication:
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American Astronomical Society Meeting Abstracts #235
- Pub Date:
- January 2020
- Bibcode:
- 2020AAS...23540705K