arXiv subjects

Adriano Fontana

Publications and source records attributed to Adriano Fontana.

At least 109 records · Page 6Linked to original sources

arXiv2017

ALMA [CII] detection of a redshift 7 lensed galaxy behind RXJ1347.1-1145

We present the results of ALMA spectroscopic follow-up of a $z=6.765$ Lyman-$α$ emitting galaxy behind the cluster RXJ1347-1145. We report the detection of [CII]158$μ$m line fully consistent with the Lyman-$α$ redshift and with the peak of the optical emission. Given the magnification of $μ=5.0 \pm 0.3$ the intrinsic (corrected for lensing) luminosity of the [CII] line is $L_{[CII]} =1.4^{+0.2}_{-0.3} \times 10^7L_{\odot}$, which is ${\sim}5$ times fainter than other detections of $z\sim 7$ galaxies. The result indicates that low $L_{[CII]}$ in $z\sim 7$ galaxies compared to the local counterparts might be caused by their low metallicities and/or feedback. The small velocity off-set ($Δv = 20_{-40}^{+140} \rm km/s$) between the Lyman-$α$ and [CII] line is unusual, and may be indicative of ionizing photons escaping.

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arXiv2016

Evidence for Reduced Specific Star Formation Rates in the Centers of Massive Galaxies at z = 4

We perform the first spatially-resolved stellar population study of galaxies in the early universe (z = 3.5 - 6.5), utilizing the Hubble Space Telescope Cosmic Assembly Near-infrared Deep Extragalactic Legacy Survey (CANDELS) imaging dataset over the GOODS-S field. We select a sample of 418 bright and extended galaxies at z = 3.5 - 6.5 from a parent sample of ~ 8000 photometric-redshift selected galaxies from Finkelstein et al. (2015). We first examine galaxies at 3.5< z < 4.0 using additional deep K-band survey data from the HAWK-I UDS and GOODS Survey (HUGS) which covers the 4000A break at these redshifts. We measure the stellar mass, star formation rate, and dust extinction for galaxy inner and outer regions via spatially-resolved spectral energy distribution fitting based on a Markov Chain Monte Carlo algorithm. By comparing specific star formation rates (sSFRs) between inner and outer parts of the galaxies we find that the majority of galaxies with the high central mass densities show evidence for a preferentially lower sSFR in their centers than in their outer regions, indicative of reduced sSFRs in their central regions. We also study galaxies at z ~ 5 and 6 (here limited to high spatial resolution in the rest-frame ultraviolet only), finding that they show sSFRs which are generally independent of radial distance from the center of the galaxies. This indicates that stars are formed uniformly at all radii in massive galaxies at z ~ 5 - 6, contrary to massive galaxies at z < 4.

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arXiv2016

The Grism Lens-Amplified Survey from Space (GLASS) X. Sub-kpc resolution gas-phase metallicity maps at cosmic noon behind the Hubble Frontier Fields cluster MACS1149.6+2223

(Abridged) We combine deep HST grism spectroscopy with a new Bayesian method to derive maps of gas-phase metallicity, nebular dust extinction, and star-formation rate for 10 star-forming galaxies at high redshift ($1.2<z<2.3$). Exploiting lensing magnification by the foreground cluster MACS1149.6+2223, we reach sub-kpc spatial resolution and push the stellar mass limit associated with such high-z spatially resolved measurements below $10^8M_\odot$ for the first time. Our maps exhibit diverse morphologies, indicative of various effects such as efficient radial mixing from tidal torques, rapid accretion of low-metallicity gas, etc., which can affect the gas and metallicity distributions in individual galaxies. Based upon an exhaustive sample of all existing sub-kpc metallicity gradients at high-z, we find that predictions given by analytical chemical evolution models assuming a relatively extended star-formation profile in the early disk formation phase can explain the majority of observed gradients, without involving galactic feedback or radial outflows. We observe a tentative correlation between stellar mass and metallicity gradient, consistent with the downsizing galaxy formation picture that more massive galaxies are more evolved into a later phase of disk growth, where they experience more coherent mass assembly at all radii and thus show shallower metallicity gradients. In addition, we compile a sample of homogeneously cross-calibrated integrated metallicity measurements spanning three orders of magnitude in stellar mass at $z\sim1.8$. We use this sample to study the mass-metallicity relation (MZR) and test the fundamental metallicity relation (FMR). The slope of the observed MZR can rule out the momentum-driven wind model at 3-$σ$ confidence level. We find no significant offset with respect to the FMR, taking into account the intrinsic scatter and measurement uncertainties.

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arXiv2016

Galaxy Zoo: Quantitative Visual Morphological Classifications for 48,000 galaxies from CANDELS

We present quantified visual morphologies of approximately 48,000 galaxies observed in three Hubble Space Telescope legacy fields by the Cosmic And Near-infrared Deep Extragalactic Legacy Survey (CANDELS) and classified by participants in the Galaxy Zoo project. 90% of galaxies have z < 3 and are observed in rest-frame optical wavelengths by CANDELS. Each galaxy received an average of 40 independent classifications, which we combine into detailed morphological information on galaxy features such as clumpiness, bar instabilities, spiral structure, and merger and tidal signatures. We apply a consensus-based classifier weighting method that preserves classifier independence while effectively down-weighting significantly outlying classifications. After analysing the effect of varying image depth on reported classifications, we also provide depth-corrected classifications which both preserve the information in the deepest observations and also enable the use of classifications at comparable depths across the full survey. Comparing the Galaxy Zoo classifications to previous classifications of the same galaxies shows very good agreement; for some applications the high number of independent classifications provided by Galaxy Zoo provides an advantage in selecting galaxies with a particular morphological profile, while in others the combination of Galaxy Zoo with other classifications is a more promising approach than using any one method alone. We combine the Galaxy Zoo classifications of "smooth" galaxies with parametric morphologies to select a sample of featureless disks at 1 < z < 3, which may represent a dynamically warmer progenitor population to the settled disk galaxies seen at later epochs.

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arXiv2016

The evolution of star formation histories of quiescent galaxies

Although there has been much progress in understanding how galaxies evolve, we still do not understand how and when they stop forming stars and become quiescent. We address this by applying our galaxy spectral energy distribution models, which incorporate physically motivated star formation histories (SFHs) from cosmological simulations, to a sample of quiescent galaxies at $0.2<z<2.1$. A total of 845 quiescent galaxies with multi-band photometry spanning rest-frame ultraviolet through near-infrared wavelengths are selected from the CANDELS dataset. We compute median SFHs of these galaxies in bins of stellar mass and redshift. At all redshifts and stellar masses, the median SFHs rise, reach a peak, and then decline to reach quiescence. At high redshift, we find that the rise and decline are fast, as expected because the Universe is young. At low redshift, the duration of these phases depends strongly on stellar mass. Low-mass galaxies ($\log(M_{\ast}/M_{\odot})\sim9.5$) grow on average slowly, take a long time to reach their peak of star formation ($\gtrsim 4$ Gyr), and the declining phase is fast ($\lesssim 2$ Gyr). Conversely, high-mass galaxies ($\log(M_{\ast}/M_{\odot})\sim11$) grow on average fast ($\lesssim 2$ Gyr), and, after reaching their peak, decrease the star formation slowly ($\gtrsim 3$ Gyr). These findings are consistent with galaxy stellar mass being a driving factor in determining how evolved galaxies are, with high-mass galaxies being the most evolved at any time (i.e., downsizing). The different durations we observe in the declining phases also suggest that low- and high-mass galaxies experience different quenching mechanisms that operate on different timescales.

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arXiv2016

Ultra-deep Ks-band Imaging of the Hubble Frontier Fields

We present an overview of the "KIFF" project, which provides ultra-deep Ks-band imaging of all six of the Hubble Frontier Fields clusters Abell 2744, MACS-0416, Abell S1063, Abell 370, MACS-0717 and MACS-1149. All of these fields have recently been observed with large allocations of Directors' Discretionary Time with the HST and Spitzer telescopes covering 0.4 < lambda < 1.6 microns and 3.6--4.5 microns, respectively. VLT/HAWK-I integrations of the first four fields reach 5-sigma limiting depths of Ks~26.0 (AB, point sources) and have excellent image quality (FWHM ~ 0."4). Shorter Keck/MOSFIRE integrations of the MACS-0717 (MACS-1149) field better observable in the north reach limiting depths Ks=25.5 (25.1) with seeing FWHM ~0."4 (0."5). In all cases the Ks-band mosaics cover the primary cluster and parallel HST/ACS+WFC3 fields. The total area of the Ks-band coverage is 490 arcmin^2. The Ks-band at 2.2 microns crucially fills the gap between the reddest HST filter (1.6 micron ~ H-band) and the IRAC 3.6 micron passband. While reaching the full depths of the space-based imaging is not currently feasible from the ground, the deep Ks-band images provide important constraints on both the redshifts and the stellar population properties of galaxies extending well below the characteristic stellar mass across most of the age of the universe, down to, and including, the redshifts of the targeted galaxy clusters (z < 0.5).

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arXiv2016

The Evolution of the Galaxy Stellar Mass Function at z= 4-8: A Steepening Low-mass-end Slope with Increasing Redshift

We present galaxy stellar mass functions (GSMFs) at $z=$ 4-8 from a rest-frame ultraviolet (UV) selected sample of $\sim$4500 galaxies, found via photometric redshifts over an area of $\sim$280 arcmin$^2$ in the CANDELS/GOODS fields and the Hubble Ultra Deep Field. The deepest Spitzer/IRAC data yet-to-date and the relatively large volume allow us to place a better constraint at both the low- and high-mass ends of the GSMFs compared to previous space-based studies from pre-CANDELS observations. Supplemented by a stacking analysis, we find a linear correlation between the rest-frame UV absolute magnitude at 1500 Å ($M_{\rm UV}$) and logarithmic stellar mass ($\log M_*$) that holds for galaxies with $\log(M_*/M_{\odot}) \lesssim 10$. We use simulations to validate our method of measuring the slope of the $\log M_*$-$M_{\rm UV}$ relation, finding that the bias is minimized with a hybrid technique combining photometry of individual bright galaxies with stacked photometry for faint galaxies. The resultant measured slopes do not significantly evolve over $z=$ 4-8, while the normalization of the trend exhibits a weak evolution toward lower masses at higher redshift. We combine the $\log M_*$-$M_{\rm UV}$ distribution with observed rest-frame UV luminosity functions at each redshift to derive the GSMFs, finding that the low-mass-end slope becomes steeper with increasing redshift from $α=-1.55^{+0.08}_{-0.07}$ at $z=4$ to $α=-2.25^{+0.72}_{-0.35}$ at $z=8$. The inferred stellar mass density, when integrated over $M_*=10^8$-$10^{13} M_{\odot}$, increases by a factor of $10^{+30}_{-2}$ between $z=7$ and $z=4$ and is in good agreement with the time integral of the cosmic star formation rate density.

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arXiv2016

Keck/MOSFIRE Spectroscopy of z=7-8 Galaxies: Ly$α$ Emission from a Galaxy at z=7.66

We report the results from some of the deepest Keck/Multi-Object Spectrometer For Infra-Red Exploration data yet obtained for candidate $z \gtrsim 7$ galaxies. Our data show one significant line detection with 6.5$σ$ significance in our combined 10 hr of integration which is independently detected on more than one night, thus ruling out the possibility that the detection is spurious. The asymmetric line profile and non-detection in the optical bands strongly imply that the detected line is Ly$α$ emission from a galaxy at $z$(Ly$α)=7.6637 \pm 0.0011$, making it the fourth spectroscopically confirmed galaxy via Ly$α$ at $z>7.5$. This galaxy is bright in the rest-frame ultraviolet (UV; $M_{\rm UV} \sim -21.2$) with a moderately blue UV slope ($β=-2.2^{+0.3}_{-0.2}$), and exhibits a rest-frame Ly$α$ equivalent width of EW(Ly$α$) $\sim 15.6^{+5.9}_{-3.6}$ Å. The non-detection of the 11 other $z \sim$ 7-8 galaxies in our long 10 hr integration, reaching a median 5$σ$ sensitivity of 28 Å in the rest-frame EW(Ly$α$), implies a 1.3$σ$ deviation from the null hypothesis of a non-evolving distribution in the rest-frame EW(Ly$α$) between $3 6.5$, which may signal the evolving neutral fraction in the intergalactic medium at the end of the reionization epoch, although our weak evidence suggests the need for a larger statistical sample to allow for a more robust conclusion.

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arXiv2016

Detection of Lyman-Alpha Emission From a Triple Imaged z=6.85 Galaxy Behind MACS J2129.4-0741

We report the detection of Ly$α$ emission at $\sim9538$Å in the Keck/DEIMOS and \HST WFC3 G102 grism data from a triply-imaged galaxy at $z=6.846\pm0.001$ behind galaxy cluster MACS J2129.4$-$0741. Combining the emission line wavelength with broadband photometry, line ratio upper limits, and lens modeling, we rule out the scenario that this emission line is \oii at $z=1.57$. After accounting for magnification, we calculate the weighted average of the intrinsic Ly$α$ luminosity to be $\sim1.3\times10^{42}~\mathrm{erg}~\mathrm{s}^{-1}$ and Ly$α$ equivalent width to be $74\pm15$Å. Its intrinsic UV absolute magnitude at 1600Å is $-18.6\pm0.2$ mag and stellar mass $(1.5\pm0.3)\times10^{7}~M_{\odot}$, making it one of the faintest (intrinsic $L_{UV}\sim0.14~L_{UV}^*$) galaxies with Ly$α$ detection at $z\sim7$ to date. Its stellar mass is in the typical range for the galaxies thought to dominate the reionization photon budget at $z\gtrsim7$; the inferred Ly$α$ escape fraction is high ($\gtrsim 10$\%), which could be common for sub-$L^*$ $z\gtrsim7$ galaxies with Ly$α$ emission. This galaxy offers a glimpse of the galaxy population that is thought to drive reionization, and it shows that gravitational lensing is an important avenue to probe the sub-$L^*$ galaxy population.

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arXiv2016

The Grism Lens-Amplified Survey from Space (GLASS). VI. Comparing the Mass and Light in MACSJ0416.1-2403 using Frontier Field imaging and GLASS spectroscopy

We present a strong and weak gravitational lens model of the galaxy cluster MACSJ0416.1-2403, constrained using spectroscopy from the Grism Lens-Amplified Survey from Space (GLASS) and Hubble Frontier Fields (HFF) imaging data. We search for emission lines in known multiply imaged sources in the GLASS spectra, obtaining secure spectroscopic redshifts of 31 multiple images belonging to 16 distinct source galaxies. The GLASS spectra provide the first spectroscopic measurements for 6 of the source galaxies. The weak lensing signal is acquired from 884 galaxies in the F606W HFF image. By combining the weak lensing constraints with 15 multiple image systems with spectroscopic redshifts and 9 multiple image systems with photometric redshifts, we reconstruct the gravitational potential of the cluster on an adaptive grid. The resulting total mass density map is compared with a stellar mass density map obtained from the deep Spitzer Frontier Fields imaging data to study the relative distribution of stellar and total mass in the cluster. We find that the projected stellar mass to total mass ratio, $f_{\star}$, varies considerably with the stellar surface mass density. The mean projected stellar mass to total mass ratio is $\langle f_{\star} \rangle= 0.009 \pm 0.003 $ (stat.), but with a systematic error as large as $0.004-0.005$, dominated by the choice of the IMF. We find agreement with several recent measurements of $f_{\star}$ in massive cluster environments. The lensing maps of convergence, shear, and magnification are made available to the broader community in the standard HFF format.

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arXiv2016

Spitzer UltRa Faint SUrvey Program (SURFS UP). II. IRAC-Detected Lyman-Break Galaxies at 6 < z < 10 Behind Strong-Lensing Clusters

We study the stellar population properties of the IRAC-detected $6 \lesssim z \lesssim 10$ galaxy candidates from the Spitzer UltRa Faint SUrvey Program (SURFS UP). Using the Lyman Break selection technique, we find a total of 16 new galaxy candidates at $6 \lesssim z \lesssim 10$ with $S/N \geq 3$ in at least one of the IRAC $3.6μ$m and $4.5μ$m bands. According to the best mass models available for the surveyed galaxy clusters, these IRAC-detected galaxy candidates are magnified by factors of $\sim 1.2$--$5.5$. We find that the IRAC-detected $6 \lesssim z \lesssim 10$ sample is likely not a homogeneous galaxy population: some are relatively massive (stellar mass as high as $4 \times 10^9\,M_{\odot}$) and evolved (age $\lesssim 500$ Myr) galaxies, while others are less massive ($M_{\text{stellar}}\sim 10^8\,M_{\odot}$) and very young ($\sim 10$ Myr) galaxies with strong nebular emission lines that boost their rest-frame optical fluxes. We identify two Ly$α$ emitters in our sample from the Keck DEIMOS spectra, one at $z_{\text{Ly}α}=6.76$ (in RXJ1347) and one at $z_{\text{Ly}α}=6.32$ (in MACS0454). We show that IRAC $[3.6]-[4.5]$ color, when combined with photometric redshift, can be used to identify galaxies likely with strong nebular emission lines within certain redshift windows.

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arXiv2015

The Grism Lens-Amplified Survey from Space (GLASS). V. Extent and spatial distribution of star formation in z~0.5 cluster galaxies

We present the first study of the spatial distribution of star formation in z~0.5 cluster galaxies. The analysis is based on data taken with the Wide Field Camera 3 as part of the Grism Lens-Amplified Survey from Space (GLASS). We illustrate the methodology by focusing on two clusters (MACS0717.5+3745 and MACS1423.8+2404) with different morphologies (one relaxed and one merging) and use foreground and background galaxies as field control sample. The cluster+field sample consists of 42 galaxies with stellar masses in the range 10^8-10^11 M_sun, and star formation rates in the range 1-20 M_sun/yr. Both in clusters and in the field, Hα is more extended than the rest-frame UV continuum in 60% of the cases, consistent with diffuse star formation and inside out growth. In ~20% of the cases, the Hα emission appears more extended in cluster galaxies than in the field, pointing perhaps to ionized gas being stripped and/or star formation being enhanced at large radii. The peak of the Hα emission and that of the continuum are offset by less than 1 kpc. We investigate trends with the hot gas density as traced by the X-ray emission, and with the surface mass density as inferred from gravitational lens models and find no conclusive results. The diversity of morphologies and sizes observed in H_alpha illustrates the complexity of the environmental process that regulate star formation. Upcoming analysis of the full GLASS dataset will increase our sample size by almost an order of magnitude, verifying and strengthening the inference from this initial dataset.

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arXiv2015

The Evolution of the Galaxy Rest-Frame Ultraviolet Luminosity Function Over the First Two Billion Years

We present a robust measurement and analysis of the rest-frame ultraviolet (UV) luminosity function at z=4-8. We use deep Hubble Space Telescope imaging over the CANDELS/GOODS fields, the Hubble Ultra Deep Field and the Year 1 Hubble Frontier Field deep parallel observations. These surveys provides an effective volume of 0.6-1.2 x 10^6 Mpc^3 over this epoch, allowing us to perform a robust search for faint (M_UV=-18) and bright (M_UV < -21) galaxies. We select candidate galaxies using a well-tested photometric redshift technique with careful screening of contaminants, finding a sample of 7446 galaxies at 3.5 1000 galaxies at z~6-8. We measure the luminosity function using a Markov Chain Monte Carlo analysis to measure robust uncertainties. At the faint end our results agree with previous studies, yet we find a higher abundance of UV-bright galaxies at z>6, with M* ~ -21 at z>5, different than that inferred based on previous trends at lower redshift. At z=8, a single power-law provides an equally good fit to the UV luminosity function, while at z=6 and 7, an exponential cutoff at the bright-end is moderately preferred. We compare to semi-analytical models, and find that the lack of evolution in M* is consistent with models where the impact of dust attenuation on the bright-end of the luminosity function decreases at higher redshift. We measure the evolution of the cosmic star-formation rate density, correcting for dust attenuation, and find that it declines as (1+z)^(-4.3 +/- 0.5) at z>4, consistent with observations at z>9. Our observations are consistent with a reionization history that starts at z>10, completes at z>6, and reaches a midpoint (x_HII = 0.5) at 6.7<z<9.4. Finally, our observations predict that the abundance of bright z=9 galaxies is likely higher than previous constraints, though consistent with recent estimates of bright z~10 galaxies. [abridged]

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arXiv2015

A Critical Assessment of Stellar Mass Measurement Methods

In this paper we perform a comprehensive study of the main sources of random and systematic errors in stellar mass measurement for galaxies using their Spectral Energy Distributions (SEDs). We use mock galaxy catalogs with simulated multi-waveband photometry (from U-band to mid-infrared) and known redshift, stellar mass, age and extinction for individual galaxies. Given different parameters affecting stellar mass measurement (photometric S/N ratios, SED fitting errors, systematic effects, the inherent degeneracies and correlated errors), we formulated different simulated galaxy catalogs to quantify these effects individually. We studied the sensitivity of stellar mass estimates to the codes/methods used, population synthesis models, star formation histories, nebular emission line contributions, photometric uncertainties, extinction and age. For each simulated galaxy, the difference between the input stellar masses and those estimated using different simulation catalogs, $Δ\log(M)$, was calculated and used to identify the most fundamental parameters affecting stellar masses. We measured different components of the error budget, with the results listed as follows: (1). no significant bias was found among different codes/methods, with all having comparable scatter; (2). A source of error is found to be due to photometric uncertainties and low resolution in age and extinction grids; (3). The median of stellar masses among different methods provides a stable measure of the mass associated with any given galaxy; (4). The deviations in stellar mass strongly correlate with those in age, with a weaker correlation with extinction; (5). the scatter in the stellar masses due to free parameters are quantified, with the sensitivity of the stellar mass to both the population synthesis codes and inclusion of nebular emission lines studied.

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arXiv2015

The Science Case for Multi-Object Spectroscopy on the European ELT

This White Paper presents the scientific motivations for a multi-object spectrograph (MOS) on the European Extremely Large Telescope (E-ELT). The MOS case draws on all fields of contemporary astronomy, from extra-solar planets, to the study of the halo of the Milky Way and its satellites, and from resolved stellar populations in nearby galaxies out to observations of the earliest 'first-light' structures in the partially-reionised Universe. The material presented here results from thorough discussions within the community over the past four years, building on the past competitive studies to agree a common strategy toward realising a MOS capability on the E-ELT. The cases have been distilled to a set of common requirements which will be used to define the MOSAIC instrument, entailing two observational modes ('high multiplex' and 'high definition'). When combined with the unprecedented sensitivity of the E-ELT, MOSAIC will be the world's leading MOS facility. In analysing the requirements we also identify a high-multiplex MOS for the longer-term plans for the E-ELT, with an even greater multiplex (>1000 targets) to enable studies of large-scale structures in the high-redshift Universe. Following the green light for the construction of the E-ELT the MOS community, structured through the MOSAIC consortium, is eager to realise a MOS on the E-ELT as soon as possible. We argue that several of the most compelling cases for ELT science, in highly competitive areas of modern astronomy, demand such a capability. For example, MOS observations in the early stages of E-ELT operations will be essential for follow-up of sources identified by the James Webb Space Telescope (JWST). In particular, multi-object adaptive optics and accurate sky subtraction with fibres have both recently been demonstrated on sky, making fast-track development of MOSAIC feasible.

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arXiv2015

Multiple Images of a Highly Magnified Supernova Formed by an Early-Type Cluster Galaxy Lens

In 1964, Refsdal hypothesized that a supernova whose light traversed multiple paths around a strong gravitational lens could be used to measure the rate of cosmic expansion. We report the discovery of such a system. In Hubble Space Telescope imaging, we have found four images of a single supernova forming an Einstein cross configuration around a redshift z=0.54 elliptical galaxy in the MACS J1149.6+2223 cluster. The cluster's gravitational potential also creates multiple images of the z=1.49 spiral supernova host galaxy, and a future appearance of the supernova elsewhere in the cluster field is expected. The magnifications and staggered arrivals of the supernova images probe the cosmic expansion rate, as well as the distribution of matter in the galaxy and cluster lenses.

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arXiv2015

A WFC3 Grism Emission Line Redshift Catalog in the GOODS-South Field

We combine HST/WFC3 imaging and G141 grism observations from the CANDELS and 3D-HST surveys to produce a catalog of grism spectroscopic redshifts for galaxies in the CANDELS/GOODS-South field. The WFC3/G141 grism spectra cover a wavelength range of 1.1 0.6. The resulting spectra are visually inspected to identify emission lines and redshifts are determined using cross-correlation with empirical spectral templates. To establish the accuracy of our redshifts, we compare our results against high-quality spectroscopic redshifts from the literature. Using a sample of 411 control galaxies, this analysis yields a precision of sigma_NMAD=0.0028 for the grism-derived redshifts, which is consistent with the accuracy reported by the 3D-HST team. Our final catalog covers an area of 153 square arcmin and contains 1019 redshifts for galaxies in GOODS-S. Roughly 60% (608/1019) of these redshifts are for galaxies with no previously published spectroscopic redshift. These new redshifts span a range of 0.677 < z < 3.456 and have a median redshift of z=1.282. The catalog contains a total of 234 new redshifts for galaxies at z>1.5. In addition, we present 20 galaxy pair candidates identified for the first time using the grism redshifts in our catalog, including four new galaxy pairs at z~2, nearly doubling the number of such pairs previously identified.

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arXiv2015

Improving resolution and depth of astronomical observations via modern mathematical methods for image analysis

In the past years modern mathematical methods for image analysis have led to a revolution in many fields, from computer vision to scientific imaging. However, some recently developed image processing techniques successfully exploited by other sectors have been rarely, if ever, experimented on astronomical observations. We present here tests of two classes of variational image enhancement techniques: "structure-texture decomposition" and "super-resolution" showing that they are effective in improving the quality of observations. Structure-texture decomposition allows to recover faint sources previously hidden by the background noise, effectively increasing the depth of available observations. Super-resolution yields an higher-resolution and a better sampled image out of a set of low resolution frames, thus mitigating problematics in data analysis arising from the difference in resolution/sampling between different instruments, as in the case of EUCLID VIS and NIR imagers.

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