The Redshift Evolution of Rest-UV Spectroscopic Properties to z~5
| Autor: | Pahl, Anthony J., Shapley, Alice, Faisst, Andreas L., Capak, Peter L., Du, Xinnan, Reddy, Naveen A., Laursen, Peter, Topping, Michael W. |
|---|---|
| Rok vydání: | 2019 |
| Předmět: | |
| Druh dokumentu: | Working Paper |
| DOI: | 10.1093/mnras/staa355 |
| Popis: | We perform a comprehensive analysis of the redshift evolution of the rest-UV spectra of star-forming galaxies out to z~5. We combine new z~5 measurements of HI Ly$\alpha$ and low- and high-ionization interstellar metal absorption features with comparable measurements at z~2-4. We measure the equivalent widths of interstellar absorption features using stacked spectra in bins of Ly$\alpha$ equivalent width, performing corrections to Ly$\alpha$ strengths based on a model for the transmission of the intergalactic medium. We find a strong correlation between decreasing low-ionization absorption strength and increasing Ly$\alpha$ emission strength over the redshift range z~2-5, suggesting that both of these quantities are fundamentally linked to neutral gas covering fraction. At the highest Ly$\alpha$ equivalent widths, we observe evolution at $z\sim5$ towards greater Ly$\alpha$ emission strength at fixed low-ionization absorption strength. If we interpret the non-evolving relationship of Ly$\alpha$ emission strength and low-ionization line strength at z~2-4 as primarily reflecting the radiative transfer of Ly$\alpha$ photons, this evolution at z~5 suggests a higher intrinsic production rate of Ly$\alpha$ photons than at lower redshift. Our conclusion is supported by the joint evolution of the relationships among Ly$\alpha$ emission strength, interstellar absorption strength, and dust reddening. We perform additional analysis in bins of stellar mass, star-formation rate, UV luminosity, and age, examining how the relationships between galaxy properties and Ly$\alpha$ emission evolve towards higher redshift. We conclude that increasing intrinsic Ly$\alpha$ photon production and strong detection of nebular CIV emission (signaling lower metallicity) at z~5 indicate an elevated ionized photon production efficiency ($\xi_{\rm ion}$). Comment: 20 pages, 17 figures, accepted for publication in MNRAS |
| Databáze: | arXiv |
| Externí odkaz: |
|