Prof Gavin Dalton

Abstract:

We present basic properties of ∼3,300 emission line galaxies detected by the FastSound survey, which are mostly Hα emitters at z ∼ 1.2–1.5 in the total area of about 20 deg2 , with the Hα flux sensitivity limit of ∼ 1.6 × 10−16 erg cm−2 s −1 at 4.5 sigma. This paper presents the catalogs of the FastSound emission lines and galaxies, which is open to the public. We also present basic properties of typical FastSound Hα emitters, which have Hα luminosities of 1041.8–1043.3 erg/s, SFRs of 20–500 M⊙/yr, and stellar masses of 1010.0–1011.3 M⊙. The 3D distribution maps for the four fields of CFHTLS W1–4 are presented, clearly showing large scale clustering of galaxies at the scale of ∼ 100–600 comoving Mpc. Based on 1,105 galaxies with detections of multiple emission lines, we estimate that contamination of non-Hα lines is about 4% in the single-line emission galaxies, which are mostly [OIII]λ5007. This contamination fraction is also confirmed by the stacked spectrum of all the FastSound spectra, in which Hα, [NII]λλ6548,6583, [SII]λλ6717,6731, and [OI]λλ6300,6364 are seen.

Abstract:

We conducted observations of 12CO(J = 5-4) and dust thermal continuum emission toward 20 star-forming galaxies on the main sequence at z ∼ 1.4 using ALMA to investigate the properties of the interstellar medium. The sample galaxies are chosen to trace the distributions of star-forming galaxies in diagrams of stellar mass versus star formation rate and stellar mass versus metallicity. We detected CO emission lines from 11 galaxies. The molecular gas mass is derived by adopting a metallicity-dependent CO-to-H2 conversion factor and assuming a CO(5-4)/CO(1-0) luminosity ratio of 0.23. Masses of molecular gas and its fractions (molecular gas mass/(molecular gas mass + stellar mass)) for the detected galaxies are in the ranges of (3.9-12) × 1010 Mo and 0.25-0.94, respectively; these values are significantly larger than those in local spiral galaxies. The molecular gas mass fraction decreases with increasing stellar mass; the relation holds for four times lower stellar mass than that covered in previous studies, and the molecular gas mass fraction decreases with increasing metallicity. Stacking analyses also show the same trends. Dust thermal emissions were clearly detected from two galaxies and marginally detected from five galaxies. Dust masses of the detected galaxies are (3.9-38) × 107 Mo. We derived gas-to-dust ratios and found they are 3-4 times larger than those in local galaxies. The depletion times of molecular gas for the detected galaxies are (1.4-36) × 108 yr while the results of the stacking analysis show ∼3 × 108 yr. The depletion time tends to decrease with increasing stellar mass and metallicity though the trend is not so significant, which contrasts with the trends in local galaxies.