We use the results from the ALMA large program ASPECS, the spectroscopic survey in the Hubble Ultra Deep Field (HUDF), to constrain CO luminosity functions of galaxies and the resulting redshift evolution of ρ(H 2 ). The broad frequency range covered enables us to identify CO emission lines of different rotational transitions in the HUDF at z > 1. We find strong evidence that the CO luminosity function evolves with redshift, with the knee of the CO luminosity function decreasing in luminosity by an order of magnitude from ∼2 to the local universe. Based on Schechter fits, we estimate that

We present new deep ALMA and HST/WFC3 observations of MASOSA and VR7, two luminous Lyα emitters (LAEs) at z = 6.5, for which the UV continuum level differ by a factor four. No IR dust continuum emission is detected in either, indicating little amounts of obscured star formation and/or high dust temperatures. MASOSA, with a UV luminosity M 1500 = −20.9, compact size and very high Lyα EW 0 ≈ 145Å, is undetected in [Cii] to a limit of L [CII] < 2.2 × 10 7 L implying a metallicity Z 0.07Z . Intriguingly, our HST data indicates a red UV slope β = −1.1 ± 0.7, at odds with the low dust content. VR7, which is a bright (M 1500 = −22.4) galaxy with moderate color (β = −1.4 ± 0.3) and Lyα EW 0 = 34Å, is clearly detected in [Cii] emission (S/N=15). VR7's rest-frame UV morphology can be described by two components separated by ≈ 1.5 kpc and is globally more compact than the [Cii] emission. The global [Cii]-UV ratio indicates Z ≈ 0.2Z , but there are large variations in the UV-[Cii] ratio on kpc scales. We also identify diffuse, possibly outflowing, [Cii]-emitting gas at ≈ 100 km s −1 with respect to the peak. VR7 appears assembling its components at a slightly more evolved stage than other luminous LAEs, with outflows already shaping its direct environment at z ∼ 7. Our results further indicate that the global [Cii]-UV relation steepens at SFR < 30 M yr −1 , naturally explaining why the [Cii]-UV ratio is anti-correlated with Lyα EW in many, but not all, observed LAEs.

We make use of sensitive (9.3 μJy beam −1 rms) 1.2 mm continuum observations from the Atacama Large Millimeter/submillimeter Array (ALMA) Spectroscopic Survey in the Hubble Ultra-Deep Field (ASPECS) large program to probe dust-enshrouded star formation from 1362 Lyman-break galaxies spanning the redshift range z=1.5-10 (to ∼7-28 M e yr −1 at 4σ over the entire range). We find that the fraction of ALMA-detected galaxies in our z=1.5-10 samples increases steeply with stellar mass, with the detection fraction rising from 0% at 10 9.0 M e to-+ 85 18 9 % at >10 10 M e. Moreover, on stacking all 1253 low-mass (<10 9.25 M e) galaxies over the ASPECS footprint, we find a mean continuum flux of −0.1±0.4 μJy beam −1 , implying a hard upper limit on the obscured star formation rate of <0.6 M e yr −1 (4σ) in a typical low-mass galaxy. The correlation between the infrared excess (IRX) of UV-selected galaxies (L IR /L UV) and the UV-continuum slope is also seen in our ASPECS data and shows consistency with a Calzetti-like relation at >  M 10 9.5 and an SMC-like relation at lower masses. Using stellar mass and β measurements for z∼2 galaxies over the Cosmic Assembly Near-infrared Deep Extragalactic Legacy Survey, we derive a new empirical relation between β and stellar mass and then use this correlation to show that our IRX-β and IRX-stellar mass relations are consistent with each other. We then use these constraints to express the IRX as a bivariate function of β and stellar mass. Finally, we present updated estimates of star formation rate density determinations at z>3, leveraging present improvements in the measured IRX and recent probes of ultraluminous far-IR galaxies at z>2. Unified Astronomy Thesaurus concepts: Lyman-break galaxies (979); Infrared excess (788); High-redshift galaxies (734); Dust continuum emission (412); Far infrared astronomy (529)

We investigate the CO excitation and interstellar medium (ISM) conditions in a cold gas mass-selected sample of 22 star-forming galaxies at z=0.46-3.60, observed as part of the ALMA Spectroscopic Survey in the Hubble Ultra Deep Field (ASPECS). Combined with Very Large Array follow-up observations, we detect a total of 34 CO -J J 1 transitions with J=1 up to 8 (and an additional 21 upper limits, up to J=10) and 6 [ ] C I  P P 10 5 , comparable to the Milky Way and main-sequence galaxies at similar redshifts, and fairly high densities (10 4 cm −3), consistent with the low-J CO excitation. Our results imply a decrease in the cosmic molecular gas mass density at z2 compared to previous ASPECS measurements.

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