AN ALMA SURVEY OF SUB-MILLIMETER GALAXIES IN THE EXTENDEDCHANDRADEEP FIELD SOUTH: PHYSICAL PROPERTIES DERIVED FROM ULTRAVIOLET-TO-RADIO MODELING

Abstract

The ALESS survey has followed-up a sample of 122 sub-millimeter sources in the Extended Chandra Deep Field South at 870µm with ALMA, allowing to pinpoint the positions of sub-millimeter galaxies (SMGs) to ∼ 0.3 arcsec and to find their precise counterparts at different wavelengths. This enabled the first compilation of the multi-wavelength spectral energy distributions (SEDs) of a statistically reliable survey of SMGs. In this paper, we present a new calibration of the MAGPHYS SED modelling code that is optimized to fit these ultraviolet-to-radio SEDs of z > 1 star-forming galaxies using an energy balance technique to connect the emission from stellar populations, dust attenuation and dust emission in a physically consistent way. We derive statistically and physically robust estimates of the photometric redshifts and physical parameters (such as stellar masses, dust attenuation, star formation rates, dust masses) for the ALESS SMGs. We find that the ALESS SMGs have a median stellar mass M * = (8.9 ± 0.1) × 10 10 M ⊙ , median star formation rate SFR = 280 ± 70 M ⊙ yr −1 , median overall V -band dust attenuation A V = 1.9 ± 0.2 mag, median dust mass M dust = (5.6 ± 1.0) × 10 8 M ⊙ , and median average dust temperature T dust ≃ 40 K. We find that the average intrinsic spectral energy distribution of the ALESS SMGs resembles that of local ultra-luminous infrared galaxies in the infrared range, but the stellar emission of our average SMG is brighter and bluer, indicating lower dust attenuation, possibly because they are more extended. We explore how the average SEDs vary with different parameters (redshift, sub-millimeter flux, dust attenuation and total infrared luminosity), and we provide a new set of SMG templates that can be used to interpret other SMG observations. To put the ALESS SMGs into context, we compare their stellar masses and star formation rates with those of less actively star-forming galaxies at the same redshifts. We find that, at z ≃ 2, about half of the SMGs lie above the star-forming main sequence (with star formation rates three times larger than normal galaxies of the same stellar mass), while half are consistent with being at the high-mass end of the main sequence. At higher redshifts (z ≃ 3.5), the SMGs tend to have higher star formation rates and stellar masses, but the fraction of SMGs that lie significantly above the main sequence decreases to less than a third.

The dust content of galaxies from z = 0 to z = 9

“…This is the case for half of the observationally derived dust masses we will be quoting in this paper (Dunne, Eales & Edmunds 2003;Eales et al 2009;Clark et al 2015) as well as papers using the MAGPHYS model (da Cunha, Charlot & Elbaz 2008;da Cunha et al 2015;Clemens et al 2013) in which the dust components in thermal equilibrium are considered as two MBBs with different dust power-law emissivity indices (βwarm and β cold ).…”

A Radio-to-mm Census of Star-forming Galaxies in Protocluster 4C23.56 at Z = 2.5: Gas Mass and Its Fraction Revealed with ALMA

“…The gas mass is calculated from870μm as listed in Hodge et al (2013) (primarybeam-corrected flux, column 8 in Table 3) and by combining it with the information (i.e., M å , SFR, redshift) from another SED fitting (i.e., MAGPHYS) presented in da Cunha et al (2015). The redshift of the main sequence SMGs is restrictedto < z 3 since the 870 μm flux above > z 3 no longer traces the RJ tail, producing large uncertainties in the estimation of gas mass for the analysis of S16.…”

An ALMA view of the interstellar medium of thez= 4.77 lensed starburst SPT-S J213242-5802.9

“…Studying the ISM of these z > 4 galaxies is difficult using the rest-frame optical because of the strong dust attenuation (da Cunha et al 2015). The dust continuum and the (sub-)millimeter lines from the ISM are thus the main information we can obtain and the continuum and [CII] can now be routinely detected by ALMA (e.g., Scoville et al 2014;Capak et al 2015).…”