Observed UV continuum slopes ($\beta$) of galaxies at $z=0.40-0.75$ in the GOODS-north field

Abstract

We estimate the UV continuum slope ($\beta$) of 465 galaxies (with luminosities of 0.028 $-$ 3.3 $L_{z=0.5}^{\ast }$) in the Great Observatories Origins Survey (GOODS) Northern field in the redshift range $z=0.40-0.75$. We use two AstroSat/UVIT (N242W, N245M), two HST (F275W, F336W), and a KPNO (U) bands to sample the UV continuum slope of selected galaxies between 1215 and 2600 angstrom. The mean (median) and 1$\sigma$ scatter in the observed $\beta$ are found to be $-1.33\pm 0.07(-1.32)$ and 0.60 within the considered redshift range. We do not find any significant evolution in the mean $\beta$ within our redshift window. Our measurements add new data points to the global $\beta$ - $z$ relation in the least-explored redshift regime, further reinforcing the gradual reddening of galaxy UV continuum with cosmic time. We notice no strong consistent trend between $\beta$ and M${}_{1500}$ for the entire luminosity range $-21$ $<M_{1500}<-15$ mag. Although, the majority of the most luminous galaxies (M${}_{1500}<-19$ mag) are found to have relatively redder slopes. Using UVIT, we detect galaxies as faint as M${}_{1500}=-15.6$ mag (i.e., 0.028 $L_{z=0.5}^{\ast }$). The faintest galaxies (M${}_{1500}>-16$ mag) tend to be redder, which indicates they were less actively forming stars during this cosmic time interval. Our study highlights the unique capability of UVIT near-UV imaging to characterize the rest-frame far-UV properties of galaxies at redshift $z\sim 0.5$.

Accepted for publication in the Astrophysical Journal

References in corpus (13)

• 3D-HST WFC3-selected Photometric Catalogs in the Five CANDELS/3D-HST Fields: Photometry, Photometric Redshifts and Stellar Masses
• The Hubble Ultra Deep Field
• GOODS-HERSCHEL: star formation, dust attenuation and the FIR-radio correlation on the Main Sequence of star-forming galaxies up to z~4
• The Evolution of the IR Luminosity Function and Dust-obscured Star Formation in the Last 13 Billion Years
• Additional Calibration of the Ultra-Violet Imaging Telescope on board AstroSat
• The Evolution of the UV Luminosity Function from z ~ 0.75 to z ~ 2.5 using HST ERS WFC3/UVIS Observations
• Constraints on the star-formation rate of z~3 LBGs with measured metallicity in the CANDELS GOODS-South field
• UV Spectral-Slopes at $z=6-9$ in the Hubble Frontier Fields: Lack of Evidence for Unusual or Pop III Stellar Populations
• The VANDELS survey: the relation between UV continuum slope and stellar metallicity in star-forming galaxies at z~3
• The UV Continuum of z > 1 Star-forming Galaxies in the Hubble Ultraviolet UltraDeep Field
• Luminous Lyman-alpha Emitters with Very Blue UV-continuum Slopes at Redshift 5.7 <= z <= 6.6
• The AstroSat UV Deep Field North: the far and near ultraviolet photometric catalog
• UV slope of z$\sim$3 bright ($L>L^{\ast }$) Lyman-break galaxies in the COSMOS field

Cited by in corpus (1)

• A model for galaxy-galaxy strong lensing statistics in surveys