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Register a new userAn ALMA view of 11 Dusty Star Forming Galaxies at the peak of Cosmic Star Formation History
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We present the ALMA view of 11 main-sequence DSFGs, (sub-)millimeter selected in the GOODS-S field, and spectroscopically confirmed to be at the peak of Cosmic SFH (z = 2-3). Our study combines the analysis of galaxy SED with ALMA continuum and CO spectral emission, by using ALMA Science Archive products at the highest spatial resolution currently available for our sample (< 1 arcsec). We include galaxy multi-band images and photometry (in the optical, radio and X-rays) to investigate the interlink between dusty, gaseous and stellar components and the eventual presence of AGN. We use multi-band sizes and morphologies to gain an insight on the processes that lead galaxy evolution, e.g. gas condensation, star formation, AGN feedback. The 11 DSFGs are very compact in the (sub-)millimeter (median r(ALMA) = 1.15 kpc), while the optical emission extends tolarger radii (median r(H)/r(ALMA) = 2.05). CO lines reveal the presence of a rotating disc of molecular gas, but we can not exclude either the presence of interactions and/or molecular outflows. Images at higher (spectral and spatial) resolution are needed to disentangle from the possible scenarios. Most of the galaxies are caught in the compaction phase, when gas cools and falls into galaxy centre, fuelling the dusty burst of star formation and the growing nucleus. We expect these DSFGs to be the high-zstar-forming counterparts of massive quiescent galaxies. Some features of CO emission in three galaxies are suggestive of forthcoming/ongoing AGN feedback, that is thought to trigger the morphological transition from star-forming disks to ETGs.
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We present the results of the archaeological analysis of the stellar populations of a sample of ~4,000 galaxies observed by the SDSS-IV-MaNGA survey using Pipe3D. Based on this analysis we extract a sample of ~150,000 SFRs and stellar masses that mimic a single cosmological survey covering the redshift range between z~0 to z~7. We confirm that the Star-Forming Main Sequence holds as a tight relation in this range of redshifts, and evolves strongly in both the zero-point and slope. This evolution is different for the population of local star-forming (SFGs) and retired (RGs) galaxies, with the latter presenting a stronger evolution in the zero-point and a weaker evolution in the slope. The fraction of RGs decreases rapidly with z, particularly for those classified as RGs at z~0. Contrary to previous studies we detect RGs well above z>1, although not all of them are progenitors of local RGs. Finally, adopting the required corrections to make the survey complete in mass in a limited volume, we recover the cosmic star-formation rate (SFR), stellar mass density, and average specific SFR histories of the Universe in this wide range of look-back times, with a remarkable agreement with the values reported by various cosmological surveys. We demonstrate that the progenitors of local RGs were more actively forming stars in the past, contributing to most of the cosmic SFR density at z>0.5, and to most of the cosmic stellar mass density at any redshift. They suffer a general quenching in the SFR at z~0.35. Below this redshift the progenitors of local SFGs dominate the SFR density of the Universe.
We use high-resolution cosmological zoom-in simulations from the FIRE project to make predictions for the covering fractions of neutral hydrogen around galaxies at z=2-4. These simulations resolve the interstellar medium of galaxies and explicitly implement a comprehensive set of stellar feedback mechanisms. Our simulation sample consists of 16 main halos covering the mass range M_h~10^9-6x10^12 Msun at z=2, including 12 halos in the mass range M_h~10^11-10^12 Msun corresponding to Lyman break galaxies (LBGs). We process our simulations with a ray tracing method to compute the ionization state of the gas. Galactic winds increase the HI covering fractions in galaxy halos by direct ejection of cool gas from galaxies and through interactions with gas inflowing from the intergalactic medium. Our simulations predict HI covering fractions for Lyman limit systems (LLSs) consistent with measurements around z~2-2.5 LBGs; these covering fractions are a factor ~2 higher than our previous calculations without galactic winds. The fractions of HI absorbers arising in inflows and in outflows are on average ~50% but exhibit significant time variability, ranging from ~10% to ~90%. For our most massive halos, we find a factor ~3 deficit in the LLS covering fraction relative to what is measured around quasars at z~2, suggesting that the presence of a quasar may affect the properties of halo gas on ~100 kpc scales. The predicted covering fractions, which decrease with time, peak at M_h~10^11-10^12 Msun, near the peak of the star formation efficiency in dark matter halos. In our simulations, star formation and galactic outflows are highly time dependent; HI covering fractions are also time variable but less so because they represent averages over large areas.
The Herschel Multi-tiered Extragalactic Survey (HerMES) has identified large numbers of dusty star-forming galaxies (DSFGs) over a wide range in redshift. A detailed understanding of these DSFGs is hampered by the limited spatial resolution of Herschel. We present 870um 0.45 resolution imaging from the Atacama Large Millimeter/submillimeter Array (ALMA) of 29 HerMES DSFGs with far-infrared (FIR) flux densities in between the brightest of sources found by Herschel and fainter DSFGs found in ground-based sub-millimeter (sub-mm) surveys. We identify 62 sources down to the 5-sigma point-source sensitivity limit in our ALMA sample (sigma~0.2mJy), of which 6 are strongly lensed (showing multiple images) and 36 experience significant amplification (mu>1.1). To characterize the properties of the ALMA sources, we introduce and make use of uvmcmcfit, a publicly available Markov chain Monte Carlo analysis tool for interferometric observations of lensed galaxies. Our lens models tentatively favor intrinsic number counts for DSFGs with a steep fall off above 8mJy at 880um. Nearly 70% of the Herschel sources comprise multiple ALMA counterparts, consistent with previous research indicating that the multiplicity rate is high in bright sub-mm sources. Our ALMA sources are located significantly closer to each other than expected based on results from theoretical models as well as fainter DSFGs identified in the LABOCA ECDFS Submillimeter Survey. The high multiplicity rate and low projected separations argue in favor of interactions and mergers driving the prodigious emission from the brightest DSFGs as well as the sharp downturn above S_880=8mJy.
We explore how the estimated star formation rate (SFR) of a sample of isolated, massive dusty star-forming galaxies at early cosmic epochs ($1.5 < z < 3.5$) changes when their ultraviolet (UV) to near-infrared (NIR) spectral energy distribution is extended to longer wavelengths by adding far-infrared/sub-millimeter data to trace the reprocessed radiation from dust heated by young massive stars. We use large-area surveys with multi-wavelength datasets that include DECam UV-to-optical, VICS82 NIR, Spitzer-IRAC NIR, and Herschel-SPIRE far-infrared/sub-millimeter data. We find that the inclusion of far-infrared/sub-millimeter data leads to SFRs that span $sim$100-3500 $M_{odot} yr^{-1}$ and are higher than the extinction-corrected UV-based SFR by an average factor of $sim$3.5, and by a factor of over 10 in many individual galaxies. Our study demonstrates the importance of far-IR/sub-millimeter data for deriving accurate SFRs in massive dusty galaxies at early epochs, and underscores the need for next-generation far-IR/sub-millimeter facilities with high sensitivity, field of view, and angular resolution.
Star-forming clumps dominate the rest-frame ultraviolet morphology of galaxies at the peak of cosmic star formation. If turbulence driven fragmentation is the mechanism responsible for their formation, we expect their stellar mass function to follow a power-law of slope close to $-2$. We test this hypothesis performing the first analysis of the stellar mass function of clumps hosted in galaxies at $zsim 1-3.5$. The clump sample is gathered from the literature with similar detection thresholds and stellar masses determined in a homogeneous way. To overcome the small number statistics per galaxy (each galaxy hosts up to a few tens of clumps only), we combine all high-redshift clumps. The resulting clump mass function follows a power-law of slope $sim -1.7$ and flattens at masses below $2times 10^7$ M$_{odot}$. By means of randomly sampled clump populations, drawn out of a power-law mass function of slope $-2$, we test the effect of combining small clump populations, detection limits of the surveys, and blending on the mass function. Our numerical exercise reproduces all the features observed in the real clump mass function confirming that it is consistent with a power-law of slope $simeq -2$. This result supports the high-redshift clump formation through fragmentation in a similar fashion as in local galaxies, but under different gas conditions.
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