Observations of the High Redshift Universe

(Abridged) In these lectures aimed for non-specialists, I review progress in understanding how galaxies form and evolve. Both the star formation history and assembly of stellar mass can be empirically traced from redshifts z~6 to the present, but how the various distant populations inter-relate and how stellar assembly is regulated by feedback and environmental processes remains unclear. I also discuss how these studies are being extended to locate and characterize the earlier sources beyond z~6. Did early star-forming galaxies contribute significantly to the reionization process and over what period did this occur? Neither theory nor observations are well-developed in this frontier topic but the first results presented here provide important guidance on how we will use more powerful future facilities.Comment: To appear in `First Light in Universe', Saas-Fee Advanced Course 36, Swiss Soc. Astrophys. Astron. in press. 115 pages, 64 figures (see http://www.astro.caltech.edu/~rse/saas-fee.pdf for hi-res figs.) For lecture ppt files see http://obswww.unige.ch/saas-fee/preannouncement/course_pres/overview_f.htm

Correlations of measurements of subclinical claw horn lesions in dairy cattle

Measurements were made of the extent of sole and white line lesions on the claws of 1 15 Holstein-Friesian cows on at least three and at most 16 occasions, and some cows were followed up to their third lactation. All the measurements were made between 12 weeks before calving and 45 weeks after calving. In total, 1016 repeated observations were made. Correlations were calculated between pairs of claws, between types of lesion (sole and white line), and between pairs of the different measurements (number of lesions, proportion of the claw affected, maximum severity score and proportion of the claw affected weighted for severity). The outer hind claws had the greatest extent of lesions of both types. Spearman correlation coefficients and confidence intervals measured the strength of the association. All the associations between claws were positive, suggesting that the lesions did not occur in isolation. Sole and white line lesions were not associated at individual observation points. Lesions on the left and right claws were markedly similar, except for sole lesions on the two inner hind claws, and for white line lesions on the two outer hind claws

UV and Ly \u3b1 luminosity functions of galaxies and star formation rate density at the end of HI reionization from the VIMOS UltraDeep Survey (VUDS)

Context. The star formation rate density (SFRD) evolution presents an area of great interest in the studies of galaxy evolution and reionization. The current constraints of SFRD at z > 5 are based on the rest-frame UV luminosity functions with the data from photometric surveys. The VIMOS UltraDeep Survey (VUDS) was designed to observe galaxies at redshifts up to 6 and opened a window for measuring SFRD at z > 5 from a spectroscopic sample with a well-controlled selection function. Aims. We establish a robust statistical description of the star-forming galaxy population at the end of cosmic HI reionization (5.0 64 z 64 6.6) from a large sample of 49 galaxies with spectroscopically confirmed redshifts. We determine the rest-frame UV and Ly\u3b1 luminosity functions and use them to calculate SFRD at the median redshift of our sample z = 5.6. Methods. We selected a sample of galaxies at 5.0 64 zspec 64 6.6 from the VUDS. We cleaned our sample from low redshift interlopers using ancillary photometric data. We identified galaxies with Ly\u3b1 either in absorption or in emission, at variance with most spectroscopic samples in the literature where Ly\u3b1 emitters (LAE) dominate. We determined luminosity functions using the 1/Vmaxmethod. Results. The galaxies in this redshift range exhibit a large range in their properties. A fraction of our sample shows strong Ly\u3b1 emission, while another fraction shows Ly\u3b1 in absorption. UV-continuum slopes vary with luminosity, with a large dispersion. We find that star-forming galaxies at these redshifts are distributed along the main sequence in the stellar mass vs. SFR plane, described with a slope \u3b1 = 0.85\ub10.05.We report a flat evolution of the specific SFR compared to lower redshift measurements. We find that the UV luminosity function is best reproduced by a double power law, while a fit with a Schechter function is only marginally inferior. The Ly\u3b1 luminosity function is best fitted with a Schechter function. We derive a log SFRDUV(\u1e40 yr-1Mpc-3) = -1.45+0.06-0.08and log SFRDLy\u3b1(\u1e40 yr-1Mpc-3) = -1.40+0.07-0.08. The SFRD derived from the Ly\u3b1 luminosity function is in excellent agreement with the UV-derived SFRD after correcting for IGM absorption. Conclusions. Our new SFRD measurements at a mean redshift of z = 5.6 are 3c0.2 dex above the mean SFRD reported in Madau and Dickinson (2014, ARAandA, 52, 415), but in excellent agreement with results from Bouwens et al. (2015a, ApJ, 803, 34). These measurements confirm the steep decline of the SFRD at z > 2. The bright end of the Ly\u3b1 luminosity function has a high number density, indicating a significant star formation activity concentrated in the brightest LAE at these redshifts. LAE with equivalent width EW> 25 contribute to about 75% of the total UV-derived SFRD. While our analysis favors low dust content in 5.0 < z < 6.6, uncertainties on the dust extinction correction and associated degeneracy in spectral fitting will remain an issue, when estimating the total SFRD until future surveys extending spectroscopy to the NIR rest-frame spectral domain, such as with JWST

The ALPINE-ALMA [C II] Survey: On the nature of an extremely obscured serendipitous galaxy

We report the serendipitous discovery of a dust-obscured galaxy observed as part of the Atacama Large Millimeter Array (ALMA) Large Program to INvestigate [C ii] at Early times (ALPINE). While this galaxy is detected both in line and continuum emissions in ALMA Band 7, it is completely dark in the observed optical/near-infrared bands and only shows a significant detection in the UltraVISTA Ks band. We discuss the nature of the observed ALMA line, that is [C ii] at z 3c4.6 or high-J CO transitions at z 3c2.2. In the first case, we find a [C ii]/FIR luminosity ratio of log(L-[C m small II]/L FIR) 3c-2.5, consistent with the average value for local star-forming galaxies (SFGs). In the second case instead, the source would lie at larger CO luminosities than those expected for local SFGs and high-z submillimetre galaxies. At both redshifts, we derive the star formation rate (SFR) from the ALMA continuum and the physical parameters of the galaxy, such as the stellar mass (M 17), by fitting its spectral energy distribution. Exploiting the results of this work, we believe that our source is a 'main-sequence', dusty SFG at z = 4.6 (i.e. [C ii] emitter) with log(SFR/M 99 yr-1) 3c 1.4 and log(M 17/M\ub7) 3c9.9. As a support to this scenario our galaxy, if at this redshift, lies in a massive protocluster recently discovered at z 3c4.57, at only 3c1 proper Mpc from its centre. This work underlines the crucial role of the ALPINE survey in making a census of this class of objects, in order to unveil their contribution to the global SFR density at the end of the Reionization epoch

zCOSMOS 20k sample group catalog to z

VizieR online Data Catalogue associated with article published in journal Astronomical Journal (AAS) with title 'The zCOSMOS 20k group catalog.' (bibcode: 2012ApJ...753..121K

The ALPINE-ALMA [CII] survey: Small Ly \u3b1 -[CII] velocity offsets in main-sequence galaxies at 4.4 < z < 6

Context. The Lyman-\u3b1 line in the ultraviolet (UV) and the [CII] line in the far-infrared (FIR) are widely used tools to identify galaxies in the early Universe and to obtain insights into interstellar medium (ISM) properties in high-redshift galaxies. By combining data obtained with ALMA in band 7 at 3c320 GHz as part of the ALMA Large Program to INvestigate [CII] at Early Times (ALPINE) with spectroscopic data from DEIMOS at the Keck Observatory, VIMOS and FORS2 at the Very Large Telescope, we assembled a unique sample of 53 main-sequence star-forming galaxies at 4.4 &lt; z &lt; 6 in which we detect both the Lyman-\u3b1 line in the UV and the [CII] line in the FIR. Aims. The goal of this paper is to constrain the properties of the Ly\u3b1 emission in these galaxies in relation to other properties of the ISM. Methods. We used [CII], observed with ALMA, as a tracer of the systemic velocity of the galaxies, and we exploited the available optical spectroscopy to obtain the Ly\u3b1-[CII] and ISM-[CII] velocity offsets. Results. We find that 90% of the selected objects have Ly\u3b1-[CII] velocity offsets in the range 0 &lt; \u394vLy\u3b1 - [CII] &lt; 400 km s-1, in line with the few measurements available so far in the early Universe, and significantly smaller than those observed at lower redshifts. At the same time, we observe ISM-[CII] offsets in the range -500 &lt; \u394vISM-[CII] &lt; 0 km s-1, in line with values at all redshifts, which we interpret as evidence for outflows in these galaxies. We find significant anticorrelations between \u394vLy\u3b1-[CII] and the Ly\u3b1 rest-frame equivalent width EW0(Ly\u3b1) (or equivalently, the Ly\u3b1 escape fraction fesc(Ly\u3b1)): galaxies that show smaller \u394vLy\u3b1-[CII] have larger EW0(Ly\u3b1) and fesc(Ly\u3b1). Conclusions. We interpret these results in the framework of available models for the radiative transfer of Ly\u3b1 photons. According to the models, the escape of Ly\u3b1 photons would be favored in galaxies with high outflow velocities, producing large EW0(Ly\u3b1) and small \u394vLy\u3b1-[CII], in agreement with our observations. The uniform shell model would also predict that the Ly\u3b1 escape in galaxies with slow outflows (0 &lt; vout &lt; 300 km s-1) is mainly determined by the neutral hydrogen column density (NHI) along the line of sight, while the alternative model by Steidel et al. (2010, ApJ, 717, 289) would more highly favor a combination of NHI at the systemic velocity and covering fraction as driver of the Ly\u3b1 escape. We suggest that the increase in Ly\u3b1 escape that is observed in the literature between z 3c 2 and z 3c 6 is not due to a higher incidence of fast outflows at high redshift, but rather to a decrease in average NHI along the line of sight, or alternatively, a decrease in HI covering fraction

The ALPINE-ALMA [CII] survey: The nature, luminosity function, and star formation history of dusty galaxies up to z 726

Aims. We present the detailed characterisation of a sample of 56 sources serendipitously detected in ALMA band 7 as part of the ALMA Large Program to INvestigate CII at Early Times (ALPINE). These sources, detected in COSMOS and ECDFS, have been used to derive the total infrared luminosity function (LF) and to estimate the cosmic star formation rate density (SFRD) up to z 726. Methods. We looked for counterparts of the ALMA sources in all the available multi-wavelength (from HST to VLA) and photometric redshift catalogues. We also made use of deeper UltraVISTA and Spitzer source lists and maps to identify optically dark sources with no matches in the public catalogues. We used the sources with estimated redshifts to derive the 250 \u3bcm rest-frame and total infrared (8-1000 \u3bcm) LFs from z 720.5 to 6. Results. Our ALMA blind survey (860 \u3bcm flux density range: 3c0.3-12.5 mJy) allows us to further push the study of the nature and evolution of dusty galaxies at high-z, identifying luminous and massive sources to redshifts and faint luminosities never probed before by any far-infrared surveys. The ALPINE data are the first ones to sample the faint end of the infrared LF, showing little evolution from z 722.5 to z 726, and a "flat"slope up to the highest redshifts (i.e. 4.5 &lt; z &lt; 6). The SFRD obtained by integrating the luminosity function remains almost constant between z 722 and z 726, and significantly higher than the optical or ultra-violet derivations, showing a significant contribution of dusty galaxies and obscured star formation at high-z. About 14% of all the ALPINE serendipitous continuum sources are found to be optically and near-infrared (near-IR) dark (to a depth Ks 3c 24.9 mag). Six show a counterpart only in the mid-IR and no HST or near-IR identification, while two are detected as [C II] emitters at z 725. The six HST+near-IR dark galaxies with mid-IR counterparts are found to contribute about 17% of the total SFRD at z 725 and to dominate the high-mass end of the stellar mass function at z &gt; 3

The ALPINE-ALMA [CII] survey: Data processing, catalogs, and statistical source properties

The Atacama Large Millimeter Array (ALMA) Large Program to INvestigate [CII] at Early times (ALPINE) targets the [CII] 158 \u3bcm line and the far-infrared continuum in 118 spectroscopically confirmed star-forming galaxies between z = 4.4 and z = 5.9. It represents the first large [CII] statistical sample built in this redshift range. We present details regarding the data processing and the construction of the catalogs. We detected 23 of our targets in the continuum. To derive accurate infrared luminosities and obscured star formation rates (SFRs), we measured the conversion factor from the ALMA 158 \u3bcm rest-frame dust continuum luminosity to the total infrared luminosity (LIR) after constraining the dust spectral energy distribution by stacking a photometric sample similar to ALPINE in ancillary single-dish far-infrared data. We found that our continuum detections have a median LIR of 4.4 7 1011 L\ub7. We also detected 57 additional continuum sources in our ALMA pointings. They are at a lower redshift than the ALPINE targets, with a mean photometric redshift of 2.5 \ub1 0.2. We measured the 850 \u3bcm number counts between 0.35 and 3.5 mJy, thus improving the current interferometric constraints in this flux density range. We found a slope break in the number counts around 3 mJy with a shallower slope below this value. More than 40% of the cosmic infrared background is emitted by sources brighter than 0.35 mJy. Finally, we detected the [CII] line in 75 of our targets. Their median [CII] luminosity is 4.8 7 108 L\ub7 and their median full width at half maximum is 252 km s-1. After measuring the mean obscured SFR in various [CII] luminosity bins by stacking ALPINE continuum data, we find a good agreement between our data and the local and predicted SFR-L[CII] relations