The UV Continuum Slopes of Early Star-Forming Galaxies in JADES
| Autor: | Topping, Michael W., Stark, Daniel P., Endsley, Ryan, Whitler, Lily, Hainline, Kevin, Johnson, Benjamin D., Robertson, Brant, Tacchella, Sandro, Chen, Zuyi, Alberts, Stacey, Baker, William M., Bunker, Andrew J., Carniani, Stefano, Charlot, Stephane, Chevallard, Jacopo, Curtis-Lake, Emma, DeCoursey, Christa, Egami, Eiichi, Eisenstein, Daniel J., Ji, Zhiyuan, Maiolino, Roberto, Williams, Christina C., Willmer, Christopher N. A., Willott, Chris, Witstok, Joris |
|---|---|
| Rok vydání: | 2023 |
| Předmět: | |
| Druh dokumentu: | Working Paper |
| Popis: | The power-law slope of the rest-UV continuum ($f_{\lambda}\propto\lambda^{\beta}$) is a key metric of early star forming galaxies, providing one of our only windows into the stellar populations and physical conditions of $z>10$ galaxies. Expanding upon previous studies with limited sample sizes, we leverage deep imaging from JADES to investigate the UV slopes of 179 $z>9$ galaxies with apparent magnitudes of $m_{\rm F200W}=26-31$, which display a median UV slope of $\beta=-2.4$. We compare to a statistical sample of $z=5-9$ galaxies, finding a shift toward bluer rest-UV colors at all $\rm~M_{UV}$. The most UV-luminous $z>9$ galaxies are significantly bluer than their lower-redshift counterparts, representing a dearth of moderately-red galaxies in the first $500~$Myr. At yet earlier times, the $z>11$ galaxy population exhibits very blue UV slopes, implying very low attenuation from dust. We identify a robust sample of 44 galaxies with $\beta<-2.8$, which have SEDs requiring models of density-bounded HII regions and median ionizing photon escape fractions of $0.51$ to reproduce. Their rest-optical colors imply that this sample has weaker emission lines (median $m_{\rm F356W}-m_{\rm F444W}=0.19$ mag) than typical galaxies (median $m_{\rm F356W}-m_{\rm F444W}=0.39$ mag), consistent with the inferred escape fractions. This sample has relatively low stellar masses (median $\log(M/M_{\odot})=7.5$), and specific star-formation rates (median$=79\rm/Gyr$) nearly twice that of our full sample (median$=44\rm/Gyr$), suggesting they are more common among systems experiencing a recent upturn in star formation. We demonstrate that the shutoff of star formation provides an alternative solution for modelling of extremely blue UV colors, making distinct predictions for the rest-optical emission of these galaxies. Future spectroscopy will be required to distinguish between these physical pictures. Comment: 17 pages, 13 figures; submitted to MNRAS |
| Databáze: | arXiv |
| Externí odkaz: |
|