Search

We report on the stellar content, half-light radii and star formation rates of a sample of 10 known high-redshift ($z\gtrsim 2$) galaxies selected on strong neutral hydrogen (HI) absorption (log(N(HI)/cm$^{-2})>19$) toward background quasars. We use observations from the {\it Hubble Space Telescope} (HST) Wide Field Camera 3 in three broad-band filters to study the spectral energy distribution(SED) of the galaxies. Using careful quasar point spread function subtraction, we study their galactic environments, and perform the first systematic morphological characterisation of such absorption-selected galaxies at high redshifts. Our analysis reveals complex, irregular hosts with multiple star-forming clumps. At a spatial sampling of 0.067 arcsec per pixel (corresponding to 0.55 kpc at the median redshift of our sample), 40% of our sample requires multiple S��rsic components for an accurate modelling of the observed light distributions. Placed on the mass-size relation and the `main sequence' of star-forming galaxies, we find that absorption-selected galaxies at high redshift extend known relations determined from deep luminosity-selected surveys to an order of magnitude lower stellar mass, with objects primarily composed of star-forming, late-type galaxies. We measure half-light radii in the range $r_{1/2} \sim$ 0.4 to 2.6 kpc based on the reddest band (F160W) to trace the oldest stellar populations, and stellar masses in the range $\log (\mathrm{M}_{\star}/\mathrm{M}_{\odot}) \sim$ 8 to 10 derived from fits to the broad-band SED. Spectroscopic and SED-based star formation rates are broadly consistent, and lie in the range log(SFR/M$_{\odot} $yr$^{-1}$) $\sim$0.0 to 1.7., 17 pages, Accepted for publication in MNRAS. This revision has minor text changes

We present an overview of the CANDELS Lyman-a Emission At Reionization (CLEAR) survey. CLEAR is a 130 orbit program of the Hubble Space Telescope using the Wide Field Camera 3 (WFC3) IR G102 grism. CLEAR targets 12 pointings divided between the GOODS-N and GOODS-S fields of the Cosmic Assembly Near-IR Deep Extragalactic Legacy Survey (CANDELS). Combined with existing spectroscopic data from other programs, the full CLEAR dataset includes spectroscopic imaging of these fields over 0.8-1.7 um. In this Paper, we describe the CLEAR survey, the survey strategy, the data acquisition, reduction, processing, and science products and catalogs released alongside this paper. The catalogs include emission line fluxes and redshifts derived from the combination of the photometry and grism spectroscopy for 6048 galaxies, primarily ranging from 0.2 < z < 3. We also provide an overview of CLEAR science goals and results. In conjunction with this Paper we provide links to electronic versions of the data products, including 1D + 2D extracted spectra and emission line maps., Accepted in ApJS. 29 pages, 14 figures. The data products (1D + 2D spectra, emission line maps) and catalogs (photometric and spectroscopic catalogs of GOODS-N and GOODS-S) are available at https://archive.stsci.edu/hlsp/clear

We measure the 850-$\mu$m source densities of 46 candidate protoclusters selected from the Planck High-z catalogue (PHz) and the Planck Catalogue of Compact Sources (PCCS) that were followed up with Herschel-SPIRE and SCUBA-2. This paper aims to search for overdensities of 850-$\mu$m sources in order to select the fields that are most likely to be genuine protoclusters. Of the 46 candidate protoclusters, 25 have significant overdensities ($>$5 times the field counts), 11 have intermediate overdensities (3--5 times the field counts) and 10 have no overdensity ($, Comment: 8 pages, 1 figure, 1 table, accepted for publication in MNRAS

The Lya line in the UV and the [CII] line in the FIR are widely used tools to identify galaxies and to obtain insights into ISM properties in the early Universe. By combining data obtained with ALMA in band 7 at ~ 320 GHz as part of the ALMA Large Program to INvestigate [CII] at Early Times (ALPINE) with spectroscopic data from DEIMOS at Keck, VIMOS and FORS2 at the VLT, we assembled a unique sample of 53 main-sequence star-forming galaxies at 4.4 < z < 6 in which we detect both the Lya line and the [CII]. We used [CII], observed with ALMA, as a tracer of the systemic velocity of the galaxies, and we find that 90% of the selected objects have Lya-[CII] velocity offsets in the range 0 < Dv_Lya-[CII] < 400 km/s, in line with the few measurements available so far in the early Universe, and significantly smaller than those observed at lower z. We observe ISM-[CII] offsets in the range -500 < Dv_ISM-[CII] < 0 km/s, in line with values at all redshifts. We find significant anticorrelations between Dv_Lya-[CII] and the Lya rest-frame equivalent width EW0(Lya) (or equivalently, the Lya escape fraction f_esc(Lya)). According to available models for the radiative transfer of Lya photons, the escape of Lya photons would be favored in galaxies with high outflow velocities, in agreement with our observations. The uniform shell model would also predict that the Lya escape in galaxies with slow outflows (0 < v_out < 300 km/s) is mainly determined by the neutral hydrogen column density (NHI), while the alternative model by Steidel+10 would favor a combination of NHI and covering fraction as driver of the Lya escape. We suggest that the observed increase in Lya escape that is observed between z~2 and z~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. [abridged], Comment: 22 pages, 6 figures, accepted for publication in A&A. This version replaces the previous one

The largest Herschel extragalactic surveys, H-ATLAS and HerMES, have selected a sample of "ultrared" dusty, star-forming galaxies (DSFGs) with rising SPIRE flux densities ($S_{500} > S_{350} > S_{250}$; so-called "500 $��$m-risers") as an efficient way for identifying DSFGs at higher redshift ($z > 4$). In this paper, we present a large Spitzer follow-up program of 300 Herschel ultrared DSFGs. We have obtained high-resolution ALMA, NOEMA, and SMA data for 63 of them, which allow us to securely identify the Spitzer/IRAC counterparts and classify them as gravitationally lensed or unlensed. Within the 63 ultrared sources with high-resolution data, $\sim$65% appear to be unlensed, and $\sim$27% are resolved into multiple components. We focus on analyzing the unlensed sample by directly performing multi-wavelength spectral energy distribution (SED) modeling to derive their physical properties and compare with the more numerous $z \sim 2$ DSFG population. The ultrared sample has a median redshift of 3.3, stellar mass of 3.7 $\times$ 10$^{11}$ $M_{\odot}$, star formation rate (SFR) of 730 $M_{\odot}$yr$^{-1}$, total dust luminosity of 9.0 $\times$ 10$^{12}$ $L_{\odot}$, dust mass of 2.8 $\times$ 10$^9$ $M_{\odot}$, and V-band extinction of 4.0, which are all higher than those of the ALESS DSFGs. Based on the space density, SFR density, and stellar mass density estimates, we conclude that our ultrared sample cannot account for the majority of the star-forming progenitors of the massive, quiescent galaxies found in infrared surveys. Our sample contains the rarer, intrinsically most dusty, luminous and massive galaxies in the early universe that will help us understand the physical drivers of extreme star formation., 33 pages, 10 figures; accepted for publication in ApJS. The catalog tables will be available on ApJS and VizieR; authors' version is available now upon request

We present SCUBA-2 850-$\mu$m observations of 13 candidate starbursting protoclusters selected using Planck and Herschel data. The cumulative number counts of the 850-$\mu$m sources in 9/13 of these candidate protoclusters show significant overdensities compared to the field, with the probability $2$ protoclusters and the peak of the cosmic star-formation rate density (SFRD). We find that the 850-$\mu$m sources in our candidate protoclusters have infrared luminosities of $L_{\mathrm{IR}}\gtrsim$10$^{12}L_{\odot}$ and star-formation rates of SFR=(500-1,500)$M_{\odot}$yr$^{-1}$. By comparing with results in the literature considering only Herschel photometry, we conclude that our 13 candidate protoclusters can be categorised into four groups: six of them being high-redshift starbursting protoclusters, one being a lower-redshift cluster/protocluster, three being protoclusters that contain lensed DSFG(s) or are rich in 850-$\mu$m sources, and three regions without significant Herschel or SCUBA-2 source overdensities. The total SFRs of the candidate protoclusters are found to be comparable or higher than those of known protoclusters, suggesting our sample contains some of the most extreme protocluster population. We infer that cross-matching Planck and Herschel data is a robust method for selecting candidate protoclusters with overdensities of 850-$\mu$m sources., Comment: 30 pages, 8 figures, 5 tables, accepted for publication in MNRAS

We analyze a sample of z-dropout galaxies in the CANDELS GOODS South and UDS fields that have been targeted by a dedicated spectroscopic campaign aimed at detecting their Ly alpha line. Deep IRAC observations at 3.6 and 4.5 mu m are used to determine the strength of optical emission lines affecting these bands at z similar to 6.5-6.9 in order to (1) investigate possible physical differences between Ly alpha emitting and non-emitting sources; (2) constrain the escape fraction of ionizing photons; and. (3) provide an estimate of the specific star formation rate at high redshifts. We find evidence of strong [O III]+H beta emission in the average (stacked) SEDs of galaxies both with and without Lya emission. The blue IRAC [3.6]-[4.5] color of the stack with detected Ly alpha line can be converted into a rest-frame equivalent width EW([O III]+ H beta) = 1500(-440) (+530) angstrom assuming a flat intrinsic stellar continuum. This strong optical line emission enables a first estimate of f(esc) less than or similar to 20% on the escape fraction of ionizing photons from Ly alpha detected objects. The objects with no Ly alpha line show less extreme EW([O III]+ H beta) = 520(-150)(+170) angstrom suggesting different physical conditions of the H II regions with respect to Ly alpha-emitting ones, or a larger f(esc). The latter case is consistent with a combined evolution of f(esc) and the. neutral hydrogen fraction as an. explanation of the lack of bright Lya emission at z > 6. A lower limit on the specific star formation rate, SSFR > 9.1 Gyr(-1) for M-star = 2 x 10(9) M-circle dot galaxies at these redshifts can be derived from the spectroscopically confirmed sample.

We analyze a sample of z-dropout galaxies in the CANDELS GOODS South and UDS fields that have been targeted by a dedicated spectroscopic campaign aimed at detecting their Ly alpha line. Deep IRAC observations at 3.6 and 4.5 mu m are used to determine the strength of optical emission lines affecting these bands at z similar to 6.5-6.9 in order to (1) investigate possible physical differences between Ly alpha emitting and non-emitting sources; (2) constrain the escape fraction of ionizing photons; and. (3) provide an estimate of the specific star formation rate at high redshifts. We find evidence of strong [O III]+H beta emission in the average (stacked) SEDs of galaxies both with and without Lya emission. The blue IRAC [3.6]-[4.5] color of the stack with detected Ly alpha line can be converted into a rest-frame equivalent width EW([O III]+ H beta) = 1500(-440) (+530) angstrom assuming a flat intrinsic stellar continuum. This strong optical line emission enables a first estimate of f(esc) less than or similar to 20% on the escape fraction of ionizing photons from Ly alpha detected objects. The objects with no Ly alpha line show less extreme EW([O III]+ H beta) = 520(-150)(+170) angstrom suggesting different physical conditions of the H II regions with respect to Ly alpha-emitting ones, or a larger f(esc). The latter case is consistent with a combined evolution of f(esc) and the. neutral hydrogen fraction as an. explanation of the lack of bright Lya emission at z > 6. A lower limit on the specific star formation rate, SSFR > 9.1 Gyr(-1) for M-star = 2 x 10(9) M-circle dot galaxies at these redshifts can be derived from the spectroscopically confirmed sample.

We present Hα maps at 1 kpc spatial resolution for star-forming galaxies at z ∼ 1, made possible by the Wide Field Camera 3 grism on Hubble Space Telescope (HST). Employing this capability over all five 3D-HST/CANDELS fields provides a sample of 3200 galaxies enabling a division into subsamples based on stellar mass and star formation rate (SFR). By creating deep stacked Hα images, we reach surface brightness limits of 1 × 10-18 erg s-1 cm-2 arcsec-2, allowing us to map the distribution of ionized gas to ∼10 kpc for typical L∗ galaxies at this epoch. We find that the spatial extent of the Hα distribution increases with stellar mass as rHα = 1.5 (M∗/1010 M⊙)0.23 kpc. The Hα emission is more extended than the stellar continuum emission, consistent with inside-out assembly of galactic disks. This effect grows stronger with mass as rHα/r∗ = 1.1(M∗/1010 M⊙)0.054. We map the Hα distribution as a function of SFR(IR+UV) and find evidence for "coherent star formation" across the SFR-M∗ plane: above the main sequence (MS), Hα is enhanced at all radii; below the MS, Hα is depressed at all radii. This suggests that at all masses the physical processes driving the enhancement or suppression of star formation act throughout the disks of galaxies. At high masses (1010.5 ∗/M⊙ 11), above the MS, Hα is particularly enhanced in the center, potentially building bulges and/or supermassive black holes. Below the MS, a strong central dip in the EW(Hα), as well as the inferred specific SFR, appears. Importantly, though, across the entirety of the SFR-M∗ plane, the absolute SFR as traced by Hα is always centrally peaked, even in galaxies below the MS.

We present VLT/X-Shooter and MUSE spectroscopy of a faint F814W = 28.60 +/- 0.33 (M-UV = -17.0), low-mass (less than or similar to 10(7)M(circle dot)), and compact (R-eff = 62 pc) freshly star-forming galaxy at z = 3.1169 magnified (16x) by the Hubble Frontier Fields galaxy cluster Abell S1063. Gravitational lensing allows for a significant jump toward lowluminosity regimes, in moderately high-resolution spectroscopy (R = lambda/d lambda similar to 3000-7400). We measured C IV lambda 1548, 1550, He II lambda 1640, OIII] lambda 1661, 1666, CIII]lambda lambda 1907, 1909, H beta, [O III] lambda lambda 4959, 5007 emission lines with FWHM less than or similar to 50 km s(-1) and (de-lensed) fluxes spanning the interval 1.0 x 10(-19)-2 x 10(-18) erg s(-1) cm(-2) at signal-to-noise ratio (S/N) = 4-30. The double-peaked Ly alpha emission with Delta v(red -blue) = 280(+/- 7) km s(-1) and delensed fluxes 2.4((blue))vertical bar 8.5((red)) x 10(-18) erg s(-1) cm(-2) (S/N = 38((blue))vertical bar 110((red)) indicate a low column density of neutral hydrogen gas consistent with a highly ionized interstellar medium as also inferred from the large [O III]lambda 5007/[O II] lambda 3727 > 10 ratio. We detect C IV lambda 1548, 1550 resonant doublet in emission, each component with FWHM less than or similar to 45 km s(-1) and redshifted by + 51(+/- 10) km s(-1) relative to the systemic redshift. We interpret this as nebular emission tracing an expanding optically thin interstellar medium. Both C IV lambda 1548, 1550 and He II lambda 1640 suggest the presence of hot and massive stars (with a possible faint active galactic nucleus). The ultraviolet slope is remarkably blue, beta = -2.95 +/- 0.20 (F-lambda = lambda(beta)), consistent with a dust-free and young less than or similar to 20 Myr galaxy. Line ratios suggest an oxygen abundance 12 + log(O/H)

We present VLT/X-Shooter and MUSE spectroscopy of a faint F814W = 28.60 ± 0.33 ({M}{UV}=-17.0), low-mass (≲{10}7{M}☉ ), and compact (R eff = 62 pc) freshly star-forming galaxy at z = 3.1169 magnified (16×) by the Hubble Frontier Fields galaxy cluster Abell S1063. Gravitational lensing allows for a significant jump toward low-luminosity regimes, in moderately high-resolution spectroscopy (R=λ /dλ ∼ 3000{--}7400). We measured C IV λ 1548,1550, He II λ 1640, O III]λ 1661,1666, C III]λ λ 1907,1909, Hβ, [O III]λ λ 4959,5007 emission lines with {FWHM}≲ 50 km s-1 and (de-lensed) fluxes spanning the interval 1.0× {10}-19{--}2× {10}-18 erg s-1 cm-2 at signal-to-noise ratio (S/N) = 4-30. The double-peaked Lyα emission with {{∆ }}v({red}-{blue})=280(±7) km s-1 and de-lensed fluxes {2.4}({blue)}| {8.5}({red)}× {10}-18 erg s-1 cm-2 (S/N = {38}({blue)}| {110}({red)}) indicate a low column density of neutral hydrogen gas consistent with a highly ionized interstellar medium as also inferred from the large [O III]λ 5007/ [O II]λ 3727 \gt \quad 10 ratio. We detect C IV λ 1548,1550 resonant doublet in emission, each component with {FWHM}≲ 45 km s-1 and redshifted by +51(±10) km s-1 relative to the systemic redshift. We interpret this as nebular emission tracing an expanding optically thin interstellar medium. Both C IV λ 1548,1550 and He II λ 1640 suggest the presence of hot and massive stars (with a possible faint active galactic nucleus). The ultraviolet slope is remarkably blue, β =-2.95+/- 0.20 ({F}λ ={λ }β ), consistent with a dust-free and young ≲20 Myr galaxy. Line ratios suggest an oxygen abundance 12 + log(O/H)\quad \lt \quad 7.8. We are witnessing an early episode of star formation in which a relatively low N H I and negligible dust attenuation might favor a leakage of ionizing radiation. This galaxy currently represents a unique low-luminosity reference object for future studies of the reionization epoch with the James Webb Space Telescope. Based on observations collected at the European Southern Observatory for Astronomical research in the Southern Hemisphere under ESO programs P095.A-0840, P095.A-0653, P186.A-0798.

[Abridged] In high density environment, the gas content of galaxies is stripped, leading to a rapid quenching of their star formation activity. This dramatic environmental effect is generally not taken into account in the SFHs usually assumed to perform spectral energy distribution (SED) fitting of these galaxies, yielding to a poor fit of their stellar emission and, consequently, a biased estimate of the SFR. We aim at reproducing the SFH of galaxies that underwent a rapid star formation quenching using a truncated delayed SFH that we implemented in the SED fitting code CIGALE. We show that the ratio between the instantaneous SFR and the SFR just before the quenching ($r_{SFR}$) is well constrained as long as rest frame UV data are available. This SED modelling is applied to the Herschel Reference Survey (HRS) containing isolated galaxies and sources falling in the dense environment of the Virgo cluster. The latter are HI-deficient due to ram pressure stripping. We show that the truncated delayed SFH successfully reproduces their SED while typical SFH assumptions fail. A good correlation is found between $r_{SFR}$ and HI-def, the parameter quantifying the gas deficiency of cluster galaxies, meaning that SED fitting results can be used to provide a tentative estimate of the gas deficiency of galaxies for which HI observations are not available. The HRS galaxies are placed on the SFR-$M_*$ diagram showing that the HI-deficient sources lie in the quiescent region confirming previous studies. Using the $r_{SFR}$ parameter, we derive the SFR of these sources before quenching and show that they were previously on the main sequence relation. We show that the $r_{SFR}$ parameter is also well recovered for deeply obscured high redshift sources, as well as in absence of IR data. SED fitting is thus a powerful tool to identify galaxies that underwent a rapid star formation quenching., accepted for publication in A&A. 13 pages, 14 figures

Context. The study of large and representative samples of low-metallicity star-forming galaxies at different cosmic epochs is of great interest to the detailed understanding of the assembly history and evolution of low-mass galaxies.Aims. We present a thorough characterization of a large sample of 183 extreme emission-line galaxies (EELGs) at redshift 0.11Methods. We use multiwavelength COSMOS photometry, HST-ACS I-band imaging, and optical zCOSMOS spectroscopy to derive the main global properties of star-forming EELGs, such as sizes, stellar masses, star formation rates (SFR), and reliable oxygen abundances using both "direct" and "strong-line" methods.Results. The EELGs are extremely compact (r(50) similar to 1.3 kpc), low-mass (M-* similar to 10(7)-10(10) M-circle dot) galaxies forming stars at unusually high specific star formation rates (sSFR equivalent to SFR/M-star up to 10(-7) yr(-1)) compared to main sequence star-forming galaxies of the same stellar mass and redshift. At rest-frame UV wavelengths, the EELGs are luminous and show high surface brightness and include strong Ly alpha emitters, as revealed by GALEX spectroscopy. We show that zCOSMOS EELGs are high-ionization, low-metallicity systems, with median 12+log(O/H) = 8.16 +/- 0.21 (0.2 Z(circle dot)) including a handful of extremely metal-deficient (Conclusions. The zCOSMOS EELGs are galaxies caught in a transient and probably early period of their evolution, where they are efficiently building up a significant fraction of their present-day stellar mass in an ongoing, galaxy-wide starburst. Therefore, the EELGs constitute an ideal benchmark for comparison studies between low- and high-redshift low-mass star-forming galaxies.

Context. The study of large and representative samples of low-metallicity star-forming galaxies at different cosmic epochs is of great interest to the detailed understanding of the assembly history and evolution of low-mass galaxies. Aims. We present a thorough characterization of a large sample of 183 extreme emission-line galaxies (EELGs) at redshift 0.11 Methods. We use multiwavelength COSMOS photometry, HST-ACS I-band imaging, and optical zCOSMOS spectroscopy to derive the main global properties of star-forming EELGs, such as sizes, stellar masses, star formation rates (SFR), and reliable oxygen abundances using both "direct" and "strong-line" methods. Results. The EELGs are extremely compact (r(50) similar to 1.3 kpc), low-mass (M-* similar to 10(7)-10(10) M-circle dot) galaxies forming stars at unusually high specific star formation rates (sSFR equivalent to SFR/M-star up to 10(-7) yr(-1)) compared to main sequence star-forming galaxies of the same stellar mass and redshift. At rest-frame UV wavelengths, the EELGs are luminous and show high surface brightness and include strong Ly alpha emitters, as revealed by GALEX spectroscopy. We show that zCOSMOS EELGs are high-ionization, low-metallicity systems, with median 12+log(O/H) = 8.16 +/- 0.21 (0.2 Z(circle dot)) including a handful of extremely metal-deficient ( Conclusions. The zCOSMOS EELGs are galaxies caught in a transient and probably early period of their evolution, where they are efficiently building up a significant fraction of their present-day stellar mass in an ongoing, galaxy-wide starburst. Therefore, the EELGs constitute an ideal benchmark for comparison studies between low- and high-redshift low-mass star-forming galaxies.

We discuss new constraints on the epoch of cosmic reionization and test the assumption that most of the ionizing photons responsible arose from high redshift star-forming galaxies. Good progress has been made in charting the end of reionization through spectroscopic studies of z~6-8 QSOs, gamma-ray bursts and galaxies expected to host Lyman-alpha emission. However, the most stringent constraints on its duration have come from the integrated optical depth, tau, of Thomson scattering to the cosmic microwave background. Using the latest data on the abundance and luminosity distribution of distant galaxies from Hubble Space Telescope imaging, we simultaneously match the reduced value tau=0.066 +/- 0.012 recently reported by the Planck collaboration and the evolving neutrality of the intergalactic medium with a reionization history within 6 >10) galaxies. Our analysis strengthens the conclusion that star-forming galaxies dominated the reionization process and has important implications for upcoming 21cm experiments and searches for early galaxies with James Webb Space Telescope., Comment: Version accepted by ApJL on Mar. 2, 2015

The galaxy stellar mass function (GSMF) at high-z provides key information on star-formation history and mass assembly in the young Universe. We aimed to use the unique combination of deep optical/NIR/MIR imaging provided by HST, Spitzer and the VLT in the CANDELS-UDS, GOODS-South, and HUDF fields to determine the GSMF over the redshift range 3.54. These results confirm the unique synergy of the CANDELS+HUDF, HUGS, and SEDS surveys for the discovery and study of moderate/low-mass galaxies at high redshifts., Comment: 26 pages, 23 figures. Accepted for publication on A&A

We present deep near-infrared (NIR) J(s)-, H-, and K-s-band ISAAC imaging of the Wide Field Planetary Camera 2 (WFPC2) field of the Hubble Deep Field South (HDF-S). The 2.'5 x 2.'5 high Galactic latitude field was observed with the Very Large Telescope under the best seeing conditions, with integration times amounting to 33.6 hr in J(s), 32.3 hr in H, and 35.6 hr in K-s. We reach total AB magnitudes for point sources of 26.8, 26.2, and 26.2, respectively (3sigma), which make it the deepest ground-based NIR observation to date and the deepest K-s-band data in any field. The effective seeing of the co-added images is approximate to0."45 in J(s), approximate to0."48 in H, and approximate to0."46 in K-s. Using published WFPC2 optical data, we constructed a K-s-limited multicolor catalog containing 833 sources down to K-s,AB(tot) less than or similar to 26, of which 624 have seven-band optical-to-NIR photometry. These data allow us to select normal galaxies from their rest-frame optical properties to high redshift (z less than or similar to 4). The observations, data reduction, and properties of the final images are discussed, and we address the detection and photometry procedures that were used in making the catalog. In addition, we present deep number counts, color distributions, and photometric redshifts of the HDF-S galaxies. We find that our faint K-s-band number counts are flatter than published counts in other deep fields, which might reflect cosmic variations or different analysis techniques. Compared to the HDF-N, we find many galaxies with very red V-H colors at photometric redshifts 1.95 < z(phot) < 3.5. These galaxies are bright in K-s, with infrared colors redder than J(s)-K-s > 2. 3 (in Johnson magnitudes). Because they are extremely faint in the observed optical, they would be missed by ultraviolet optical selection techniques, such as the U-dropout method.

We present ALMA detections of the [CI] 1-0, CO J=3-2, and CO J=4-3 emission lines, as well as the ALMA band 4 continuum for a compact star-forming galaxy (cSFG) at z=2.225, 3D-HST GS30274. As is typical for cSFGs, this galaxy has a stellar mass of $1.89 \pm 0.47\,\times 10^{11}\,\rm{M}_\odot$, with a star formation rate of $214\pm44\,\rm{M}_\odot\,\rm{yr}^{-1}$ putting it on the star-forming `main-sequence', but with an H-band effective radius of 2.5 kpc, making it much smaller than the bulk of `main-sequence' star-forming galaxies. The intensity ratio of the line detections yield an ISM density (~ 6 $\times 10^{4}\,\rm{cm}^{-3}$) and a UV-radiation field ( ~2 $\times 10^4\,\rm{G}_0$), similar to the values in local starburst and ultra-luminous infrared galaxy environments. A starburst phase is consistent with the short depletion times ($t_{\rm H2, dep} \leq 140$ Myr) we find using three different proxies for the H2 mass ([CI], CO, dust mass). This depletion time is significantly shorter than in more extended SFGs with similar stellar masses and SFRs. Moreover, the gas fraction of 3D-HST GS30274 is smaller than typically found in extended galaxies. We measure the CO and [CI] kinematics and find a FWHM line width of ~$750 \pm 41 $ km s$^{-1}$. The CO and [CI] FWHM are consistent with a previously measured H$\alpha$ FWHM for this source. The line widths are consistent with gravitational motions, suggesting we are seeing a compact molecular gas reservoir. A previous merger event, as suggested by the asymmetric light profile, may be responsible for the compact distribution of gas and has triggered a central starburst event. This event gives rise to the starburst-like ISM properties and short depletion times. The centrally located and efficient star formation is quickly building up a dense core of stars, responsible for the compact distribution of stellar light in 3D-HST GS30274., Comment: Accepted for publication in A&A

We derive relations between the effective radii $R_{\rm{eff}}$ of galaxies and the virial radii $R_{200c}$ of their dark matter halos over the redshift range $0 < z < 3$. For galaxies, we use the measured sizes from deep images taken with \emph{Hubble Space Telescope} for the Cosmic Assembly Near-infrared Deep Extragalactic Legacy Survey; for halos, we use the inferred sizes from abundance matching to cosmological dark matter simulations via a stellar mass--halo mass (SMHM) relation. For this purpose, we derive a new SMHM relation based on the same selection criteria and other assumptions as for our sample of galaxies with size measurements. As a check on the robustness of our results, we also derive $R_{\rm{eff}}$--$R_{200c}$ relations for three independent SMHM relations from the literature. We find that galaxy $R_{\rm{eff}}$ is proportional on average to halo $R_{200c}$, confirming and extending to high redshifts the $z=0$ results of Kravtsov. Late-type galaxies (with low S\'ersic index and high specific star formation rate [sSFR]) follow a linear $R_{\rm{eff}}$--$R_{200c}$ relation, with effective radii at $0.5 < z < 3$ close to those predicted by simple models of disk formation; at $z < 0.5$, the sizes of late-type galaxies appear to be slightly below this prediction. Early-type galaxies (with high S\'ersic index and low sSFR) follow a roughly parallel $R_{\rm{eff}}$--$R_{200c}$ relation, $\sim$ 0.2--0.3 dex below the one for late-type galaxies. Our observational results, reinforced by recent hydrodynamical simulations, indicate that galaxies grow quasi-homologously with their dark matter halos., Comment: This version is the same as the published ApJ paper, including a few minor corrections made in proof

Supernovae are cosmic explosions of cataclysmic proportion that signify the death of a star. While being interesting phenomena in their own right, their brightness also make them excellent probes of the early universe. Depending on the type of the progenitor star and the origin of the explosion different subjects can be investigated. In this dissertation the work I have done on the detection, characterisation and rate measurements of supernovae in the Stockholm VIMOS Supernova Search is presented. We have discovered 16 supernovae that exploded billions of years ago (or, equivalently, at high redshift, z). The observed brightness and colour evolution have been used to classify the supernovae into either thermonuclear (type Ia) or core collapse (type II) supernovae. The accuracy of the classification code is high, only about 5% of the supernovae are mistyped, similar to other codes of the same kind. By comparing the observed frequency of supernovae to simulations the underlying supernova rate at these high redshifts have been measured. The main result reported in this thesis is that the core collapse supernova rate at high redshift matches the rates estimated from looking at the star formation history of the universe, and agree well with previous studies. The rate of Ia supernovae at high redshift have been investigated by several projects, our results show a somewhat higher rate of Ia supernovae than expected. Proper estimates of the systematic errors of rate measurements are found to be very important. Furthermore, by using novel techniques for reducing and stacking images, we have obtained a galaxy sample containing approximately 50,000 galaxies. Photometric redshifts have been obtained for most of the galaxies, the resulting accuracy below z=1 is on the order of 10%. The galaxy sample has also been used to find high redshift sources, so called Lyman Break Galaxies, at z=3-5. At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 2: Submitted. Paper 3: Manuscript. Paper 4: Manuscript.

We discuss the state of the assembly of the Hubble Sequence in the mix of bright galaxies at redshift 1.4< z \le 2.5 with a large sample of 1,671 galaxies down to H_{AB}~26, selected from the HST/ACS and WFC3 images of the GOODS--South field obtained as part of the GOODS and CANDELS observations. We investigate the relationship between the star formation properties and morphology using various parametric diagnostics, such as the Sersic light profile, Gini (G), M_{20}, Concentration (C), Asymmetry (A) and multiplicity parameters. Our sample clearly separates into massive, red and passive galaxies versus less massive, blue and star forming ones, and this dichotomy correlates very well with the galaxies' morphological properties. Star--forming galaxies show a broad variety of morphological features, including clumpy structures and bulges mixed with faint low surface brightness features, generally characterized by disky-type light profiles. Passively evolving galaxies, on the other hand, very often have compact light distribution and morphology typical of today's spheroidal systems. We also find that artificially redshifted local galaxies have a similar distribution with z~2galaxies in a G-M_{20} plane. Visual inspection between the rest-frame optical and UV images show that there is a generally weak morphological k-correction for galaxies at z~2, but the comparison with non-parametric measures show that galaxies in the rest-frame UV are somewhat clumpier than rest-frame optical. Similar general trends are observed in the local universe among massive galaxies, suggesting that the backbone of the Hubble sequence was already in place at z~2., 22 pages, 19 figures, ApJ accepted (added 3 references)

The Hubble Tarantula Treasury Project (HTTP) is an ongoing panchromatic imaging survey of stellar populations in the Tarantula Nebula in the Large Magellanic Cloud that reaches into the sub-solar mass regime (< 0.5 Mo). HTTP utilizes the capability of HST to operate the Advanced Camera for Surveys (ACS) and the Wide Field Camera 3 (WFC3) in parallel to study this remarkable region in the near-ultraviolet, optical, and near-infrared spectral regions, including narrow band H$\alpha$ images. The combination of all these bands provides a unique multi-band view. The resulting maps of the stellar content of the Tarantula Nebula within its main body provide the basis for investigations of star formation in an environment resembling the extreme conditions found in starburst galaxies and in the early Universe. Access to detailed properties of individual stars allows us to begin to reconstruct the evolution of the stellar skeleton of the Tarantula Nebula over space and time with parcsec-scale resolution. In this first paper we describe the observing strategy, the photometric techniques, and the upcoming data products from this survey and present preliminary results obtained from the analysis of the initial set of near-infrared observations., Comment: 14 pages, 10 Figures, 1 Table, submitted to AJ

We present a study of the environment of 27 z=3-4.5 bright quasars from the MUSE Analysis of Gas around Galaxies (MAGG) survey. With medium-depth MUSE observations (4 hours on target per field), we characterise the effects of quasars on their surroundings by studying simultaneously the properties of extended gas nebulae and Lyalpha emitters (LAEs) in the quasar host haloes. We detect extended (up to ~ 100 kpc) Lyalpha emission around all MAGG quasars, finding a very weak redshift evolution between z=3 and z=6. By stacking the MUSE datacubes, we confidently detect extended emission of CIV and only marginally detect extended HeII up to ~40 kpc, implying that the gas is metal enriched. Moreover, our observations show a significant overdensity of LAEs within 300 km/s from the quasar systemic redshifts estimated from the nebular emission. The luminosity functions and equivalent width distributions of these LAEs show similar shapes with respect to LAEs away from quasars suggesting that the Lyalpha emission of the majority of these sources is not significantly boosted by the quasar radiation or other processes related to the quasar environment. Within this framework, the observed LAE overdensities and our kinematic measurements imply that bright quasars at z=3-4.5 are hosted by haloes in the mass range ~ 10^{12.0}-10^{12.5} Msun., Comment: 23 pages, 20 figures, accepted for publication in MNRAS