Search

We present the first comprehensive release of photometric redshifts (photo-z's) from the Cosmic Assembly Near-Infrared Deep Extragalactic Legacy Survey (CANDELS) team. We use statistics based upon the Quantile-Quantile (Q--Q) plot to identify biases and signatures of underestimated or overestimated errors in photo-z probability density functions (PDFs) produced by six groups in the collaboration; correcting for these effects makes the resulting PDFs better match the statistical definition of a PDF. After correcting each group's PDF, we explore three methods of combining the different groups' PDFs for a given object into a consensus curve. Two of these methods are based on identifying the minimum f-divergence curve, i.e., the PDF that is closest in aggregate to the other PDFs in a set (analogous to the median of an array of numbers). We demonstrate that these techniques yield improved results using sets of spectroscopic redshifts independent of those used to optimize PDF modifications. The best photo-z PDFs and point estimates are achieved with the minimum f-divergence using the best 4 PDFs for each object (mFDa4) and the Hierarchical Bayesian (HB4) methods, respectively. The HB4 photo-z point estimates produced $\sigma_{\rm NMAD} = 0.0227/0.0189$ and $|\Delta z/(1+z)| > 0.15$ outlier fraction = 0.067/0.019 for spectroscopic and 3D-HST redshifts, respectively. Finally, we describe the structure and provide guidance for the use of the CANDELS photo-z catalogs, which are available at https://archive.stsci.edu/hlsp/candels., Comment: 35 pages, 19 figures, published in ApJ, data available at https://archive.stsci.edu/hlsp/candels

Star-forming dwarf galaxies have properties similar to those expected in high-redshift galaxies. Hence, these local galaxies may provide insights into the evolution of the first galaxies, and the physical processes at work. We present a sample of eleven potential local analogs to high-$z$ (LAHz) galaxies. The sample consists of blue compact dwarf galaxies, selected to have spectral energy distributions that fit galaxies at $1.5, Comment: Submitted to AAS journals. Comments are welcome

We present a WFC3 F160W ($H$-band) selected catalog in the CANDELS/GOODS-N field containing photometry from the ultraviolet (UV) to the far-infrared (IR), photometric redshifts and stellar parameters derived from the analysis of the multi-wavelength data. The catalog contains 35,445 sources over the 171 arcmin$^{2}$ of the CANDELS F160W mosaic. The 5$\sigma$ detection limits (within an aperture of radius 0\farcs17) of the mosaic range between $H=27.8$, 28.2 and 28.7 in the wide, intermediate and deep regions, that span approximately 50\%, 15\% and 35\% of the total area. The multi-wavelength photometry includes broad-band data from UV (U band from KPNO and LBC), optical (HST/ACS F435W, F606W, F775W, F814W, and F850LP), near-to-mid IR (HST/WFC3 F105W, F125W, F140W and F160W, Subaru/MOIRCS Ks, CFHT/Megacam K, and \spitzer/IRAC 3.6, 4.5, 5.8, 8.0 $\mu$m) and far IR (\spitzer/MIPS 24$\mu$m, HERSCHEL/PACS 100 and 160$\mu$m, SPIRE 250, 350 and 500$\mu$m) observations. In addition, the catalog also includes optical medium-band data (R$\sim50$) in 25 consecutive bands, $\lambda=500$ to 950~nm, from the SHARDS survey and WFC3 IR spectroscopic observations with the G102 and G141 grisms (R$\sim210$ and 130). The use of higher spectral resolution data to estimate photometric redshifts provides very high, and nearly uniform, precision from $z=0-2.5$. The comparison to 1,485 good quality spectroscopic redshifts up to $z\sim3$ yields $\Delta z$/(1+$z_{\rm spec}$)$=$0.0032 and an outlier fraction of $\eta=$4.3\%. In addition to the multi-band photometry, we release added-value catalogs with emission line fluxes, stellar masses, dust attenuations, UV- and IR- based star formation rates and rest-frame colors., Comment: The catalogs, images and spectra are available in Rainbow-slicer (https://bit.ly/2OxKKx1 ), navigator (https://bit.ly/2GDS180 ) and MAST (https://bit.ly/2YtoBQ4 ). In addition to the photometry and other added-value catalogs we release UV+IR star formation rates based on Spitzer (MIPS) and Herschel (PACS and SPIRE) in the 5 CANDELS fields

We used the Atacama Large Millimeter/submillimeter Array (ALMA) to map $^{12}$CO($J$ = 1-0), $^{12}$CO($J$ = 2-1), $^{12}$CO($J$ = 3-2), $^{13}$CO($J$ = 2-1), and [CI]($^3P_1$-$^3P_0$) emission lines around the type 1 active galactic nucleus (AGN) of NGC 7469 ($z = 0.0164$) at $\sim 100$ pc resolutions. The CO lines are bright both in the circumnuclear disk (central $\sim 300$ pc) and the surrounding starburst (SB) ring ($\sim 1$ kpc diameter), with two bright peaks on either side of the AGN. By contrast, the [CI]($^3P_1$-$^3P_0$) line is strongly peaked on the AGN. Consequently, the brightness temperature ratio of [CI]($^3P_1$-$^3P_0$) to $^{13}$CO(2-1) is $\sim 20$ at the AGN, as compared to $\sim 2$ in the SB ring. Our local thermodynamic equilibrium (LTE) and non-LTE models indicate that the enhanced line ratios (or CI enhancement) are due to an elevated C$^0$/CO abundance ratio ($\sim 3-10$) and temperature ($\sim 100-500$ K) around the AGN as compared to the SB ring (abundance ratio $\sim 1$, temperature $\lesssim 100$ K), which accords with the picture of the X-ray-dominated Region (XDR). Based on dynamical modelings, we also provide CO(1-0)-to- and [CI]($^3P_1$-$^3P_0$)-to-molecular mass conversion factors at the central $\sim 100$ pc of this AGN as $\alpha_{\rm CO} = 4.1$ and $\alpha_{\rm CI} = 4.4~M_\odot$ (K km s$^{-1}$ pc$^2$)$^{-1}$, respectively. Our results suggest that the CI enhancement is potentially a good marker of AGNs that could be used in a new submillimeter diagnostic method toward dusty environments., Comment: 25 pages, 12 figures, 8 tables. Accepted for publication in ApJ. Minor updates in a replacement

The rate of major galaxy-galaxy merging is theoretically predicted to steadily increase with redshift during the peak epoch of massive galaxy development ($1{\leq}z{\leq}3$). We use close-pair statistics to objectively study the incidence of massive galaxies (stellar $M_{1}{\geq}2{\times}10^{10}M_{\odot}$) hosting major companions ($1{\leq}M_{1}/M_{2}{\leq}4$; i.e., $$4:1) companions at $z>1$. We show that these evolutionary trends are statistically robust to changes in companion proximity. We find disagreements between published results are resolved when selection criteria are closely matched. If we compute merger rates using constant fraction-to-rate conversion factors ($C_{\mathrm{merg,pair}}{=}0.6$ and $T_{\mathrm{obs,pair}}{=}0.65\mathrm{Gyr}$), we find that MR rates disagree with theoretical predictions at $z{>}1.5$. Instead, if we use an evolving $T_{\mathrm{obs,pair}}(z){\propto}(1+z)^{-2}$ from Snyder et al., our MR-based rates agree with theory at $0{, Comment: 27 pages, 15 figures, 5 tables. Accepted for publication in Monthly Notices of the Royal Astronomical Society Main Journal

The z=0.89 molecular absorber toward PKS1830-211 provides us with the opportunity to probe the chemical and physical properties of the interstellar medium in the disk of a galaxy at a look-back time of half the present age of the Universe. Recent ALMA observations of hydrides have unveiled the multi-phase composition of this source's interstellar medium along two absorbing sightlines. Here, we report ALMA observations of CH+ and SH+, and of their 13C- and 34S- isotopologues, as potential tracers of energetic processes in the interstellar medium. CH+ and 13CH+ are detected toward both images of PKS1830-211, CH+ showing the deepest and broadest absorption among all species observed so far. The [CH+]/[13CH+] abundance ratio is ~100 in the south-west line of sight. [...] Toward the north-east image, we find an even larger value of [CH+]/[13CH+], 146 +/- 43, although with a large uncertainty. This sightline intercepts the absorber at a larger galactocentric radius than the southwestern one, where material might be less processed in stellar nucleosynthesis. In contrast to CH+ and its 13C isotopologue, SH+ and 34SH+ are only detected on the south-west sightline. These are the first detections of extragalactic SH+ and interstellar 34SH+. The spectroscopic parameters of SH+ are reevaluated and improved rest frequencies of 34SH+ are obtained. The [CH+]/[SH+] column density ratios show a large difference between the two lines of sight: ~25 and >600 toward the SW and NE image, respectively. We are not able to shed light on the formation process of CH+ and SH+ with these data, but the differences in the two sightlines toward PKS1830-211 suggest that their absorptions arise from gas with molecular fraction gtrsim 10%, with SH+ tracing significantly higher molecular fractions than CH+., accepted for publication in A&A

We present a 0.4-8$\mu$m multi-wavelength photometric catalog in the Extended Groth Strip (EGS) field. This catalog is built on the Hubble Space Telescope (HST) WFC3 and ACS data from the Cosmic Assembly Near-infrared Deep Extragalactic Legacy Survey (CANDELS), and it incorporates the existing HST data from the All-wavelength Extended Groth strip International Survey (AEGIS) and the 3D-HST program. The catalog is based on detections in the F160W band reaching a depth of F160W=26.62 AB (90% completeness, point-sources). It includes the photometry for 41457 objects over an area of $\approx 206$ arcmin$^2$ in the following bands: HST ACS F606W and F814W; HST WFC3 F125W, F140W and F160W; CFHT/Megacam $u^*$, $g'$, $r'$, $i'$ and $z'$; CFHT/WIRCAM $J$, $H$ and $K_\mathrm{S}$; Mayall/NEWFIRM $J1$, $J2$, $J3$, $H1$, $H2$, $K$; Spitzer IRAC $3.6\mu$m, $4.5\mu$m, $5.8\mu$m and $8.0\mu$m. We are also releasing value-added catalogs that provide robust photometric redshifts and stellar mass measurements. The catalogs are publicly available through the CANDELS repository., Comment: ApJS in press. Catalogs can be accessed through the MAST archive at https://archive.stsci.edu/prepds/candels/

We present a multi-wavelength photometric catalog in the COSMOS field as part of the observations by the Cosmic Assembly Near-infrared Deep Extragalactic Legacy Survey (CANDELS). The catalog is based on Hubble Space Telescope Wide Field Camera 3 (HST/WFC3) and Advanced Camera for Surveys (ACS) observations of the COSMOS field (centered at RA: $10^h00^m28^s$, Dec:$+02^{\circ}12^{\prime}21^{\prime\prime}$). The final catalog has 38671 sources with photometric data in forty two bands from UV to the infrared ($\rm \sim 0.3-8\,\mu m$). This includes broad-band photometry from the HST, CFHT, Subaru, VISTA and Spitzer Space Telescope in the visible, near infrared and infrared bands along with intermediate and narrow-band photometry from Subaru and medium band data from Mayall NEWFIRM. Source detection was conducted in the WFC3 F160W band (at $\rm 1.6\,\mu m$) and photometry is generated using the Template FITting algorithm. We further present a catalog of the physical properties of sources as identified in the HST F160W band and measured from the multi-band photometry by fitting the observed spectral energy distributions of sources against templates., Comment: 28 Pages, 22 Figures and 10 Tables. Accepted for Publication in the ApJS

We derive physical properties of 10 submillimeter galaxies located in the CANDELS coverage of the GOODS-S field. The galaxies were first identified as submillimeter sources with the LABOCA bolometer and subsequently targeted for 870um continuum observation with ALMA. The high angular resolution of the ALMA imaging allows secure counterparts to be identified in the CANDELS multiband dataset. The CANDELS data provide deep photometric data from UV through near-infrared wavelengths. Using synthetic spectral energy distributions, we derive photometric redshifts, stellar masses, extinction, ages, and the star formation history. The redshift range is z=1.65-4.76, with two of the galaxies located at z>4. Two SMG counterparts have stellar masses 2-3 orders of magnitude lower than the rest. The remaining SMG counterparts have stellar masses around 1x10^11 Msun. The stellar population in the SMGs is typically older than the expected duration of the submillimeter phase, suggesting that the star formation history of submillimeter galaxies is more complex than a single burst. Non-parametric morphology indices suggest that the SMG counterparts are among the most asymmetric systems compared with galaxies of the same stellar mass and redshift. The HST images shows that 3 of the SMGs are associated with on-going mergers. The remaining counterparts are isolated. Estimating the dust and molecular gas mass from the submm fluxes, and comparing with our stellar masses shows that the molecular gas mass fraction of SMGs is ~28% and that the final stellar mass is likely to be (1-2)x10^11 Msun., 51 pages, 9 figures, 5 tables; Submitted to ApJ

We present an ALMA survey of dust continuum emission in a sample of 70 galaxies in the redshift range z=2-5 selected from the CANDELS GOODS-S field. Multi-Epoch Abundance Matching (MEAM) is used to define potential progenitors of a z = 0 galaxy of stellar mass 1.5 10^11 M_sun. Gas masses are derived from the 850um luminosity. Ancillary data from the CANDELS GOODS-S survey are used to derive the gas mass fractions. The results at z=4. The average gas mass fraction for the detected z=2 galaxies is f_gas = 0.55+/-0.12 and f_gas = 0.62+/-0.15 for the z=3 sample. This agrees with expectations for galaxies on the star-forming main sequence, and shows that gas fractions have decreased at a roughly constant rate from z=3 to z=0. Stacked images of the galaxies not detected with ALMA give upper limits to f_gas of 4., Accepted for publication in the Astrophysical Journal. 33 pages; 11 figures

We report the detection of OH+ and H2O+ in the z=0.89 absorber toward the lensed quasar PKS1830-211. The abundance ratio of OH+ and H2O+ is used to quantify the molecular hydrogen fraction (fH2) and the cosmic-ray ionization rate of atomic hydrogen (zH) along two lines of sight, located at ~2 kpc and ~4 kpc to either side of the absorber's center. The molecular fraction decreases outwards, from ~0.04 to ~0.02, comparable to values measured in the Milky Way at similar galactocentric radii. For zH, we find values of ~2x10^-14 s^-1 and ~3x10^-15 s^-1, respectively, which are slightly higher than in the Milky Way at comparable galactocentric radii, possibly due to a higher average star formation activity in the z=0.89 absorber. The ALMA observations of OH+, H2O+, and other hydrides toward PKS1830-211 reveal the multi-phase composition of the absorbing gas. Taking the column density ratios along the southwest and northeast lines of sight as a proxy of molecular fraction, we classify the species ArH+, OH+, H2Cl+, H2O+, CH, and HF as tracing gases increasingly more molecular. Incidentally, our data allow us to improve the accuracy of H2O+ rest frequencies and thus refine the spectroscopic parameters., Comment: Accepted for publication in A&A

We have undertaken a search for millimetre-wave band absorption (through the CO and HCO+ rotational transitions) in the host galaxies of reddened radio sources (z = 0.405-1.802). Despite the colour selection (optical-near infrared colours of V - K > 5 in all but one source), no absorption was found in any of the eight quasars for which the background continuum flux was detected. On the basis of the previous (mostly intervening) H2 and OH detections, the limits reached here and in some previous surveys should be deep enough to detect molecular absorption according to their V - K colours. However, our survey makes the assumption that the reddening is associated with dust close to the emission redshift of the quasar and that the narrow millimetre component of this emission is intercepted by the compact molecular cores. By using the known millimetre absorbers to define the colour depth and comparing this with the ultra-violet luminosities of the sources, we find that, even if these assumptions are valid, only twelve of the forty objects (mainly from this work) are potentially detectable. This is assuming an excitation temperature of 10 K at z=0, with the number decreasing with increasing temperatures (to zero detectable at 100 K).

We report the detection of molecular absorption lines at z = 0.7645 toward the radio-loud quasi-stellar object (QSO) PMN 0134−0931. The CO J = 2–1 and HCO+ J = 2–1 lines are seen in absorption along two different lines of sight to lensed images of the background QSO. The lines of sight are separated by ~07, corresponding to 5 kpc in the lens plane. PMN 0134−0931 represents one out of only five known molecular absorption line systems at cosmologically significant distances. Moreover, it is also one of three such systems where the absorption occurs in a galaxy acting as a gravitational lens. The absorption lines through the two lines of sight are shifted by 215 ± 8 km s−1, possibly representing rotational motion in one of the lensing galaxies. The absorption profiles are wide, ~200 km s−1, suggesting that the absorption occurs in a highly inclined disk galaxy with a flat rotation curve and a cloud–cloud velocity dispersion ~30 km s−1. Gravitational lens models require two equal mass galaxies to account for the observed configuration of lensed images. The presence of two galaxies in close proximity means that they might be interacting and potentially merging and the kinematics of the molecular gas may not reflect ordered rotational motion. Compared with other high-redshift molecular absorption systems, the column densities of both CO and HCO+ are normal for diffuse molecular gas toward one of the lensed images, but significantly higher toward the other. Also, the abundance ratio is 2 − 3 times higher than in typical diffuse molecular gas. It is plausible that the second line of sight probes denser molecular gas than what is normally the case for absorption.

著者人数: 84名, Accepted: 2015-03-17, 資料番号: SA1150147000

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., Comment: 25 Pages, 9 Figures, submitted to AJ

著者人数: 69名, Accepted: 2015-03-13, 資料番号: SA1150146000

We present a detection of [CI] line emission in the lensed quasar APM 08279+5255 at z=3.91 using the IRAM Plateau de Bure interferometer. The [CI] line velocity and width are similar to the values of previously detected high-J CO and HCN lines in this source, suggesting that the emission from all of these species arises from the same region. The apparent luminosity of the [CI] line is L'(CI) = (3.1 +/- 0.4)x10^10 K km/s pc^2, which implies a neutral carbon mass, M(CI) = (4.4+/-0.6)/m x10^7 M_sun, where m is the lensing magnification factor. The [CI] line luminosity is consistent with the large molecular gas mass inferred from the nuclear CO line luminosity ~10^11 /m M_sun. We also present an upper limit on the H2O line luminosity in APM 08279+5255 of, L'(H2O) < 1.8x10^10 K km/s pc^2 (3-sigma)., Accepted for publication in the Astrophysical Journal

We search for massive and evolved galaxies at z ≥ 5 in the Great Observatories Origins Deep Survey (GOODS) southern field. Combining HST ACS, VLT ISAAC and Spitzer IRAC broad–band photometric data, we develop a color selection technique to identify candidates for being evolved galaxies at high redshifts. The color selection is primarily based on locating the Balmer–break using the K- and 3.6 μm bands. Stellar population synthesis models are fitted to the SEDs of these galaxies to identify the final sample. We find 11 candidates with photometric redshifts in the range 4.9 < z < 5.6, dominated by an old stellar population, with ages 0.2-1.0 Gyr, and stellar masses in the range (0.7 − 5) × 1011 M⊙. Most of the candidates have modest amounts of internal dust extinction. The majority of the stars in these galaxies were formed at z>9 and the current star formation activity is a few percent of the inferred initial star formation rate.

The combination of the collecting power of an ELT with an ultra-stable high resolution spectrograph opens up the possibility to measure for the first time directly the dynamical effect of the acceleration of the Universe. CODEX will also provide unique opportunities for advance in many other branches of astrophysics. The CODEX design is based on an array of several identical spectrographs. It is highly modular and can be easily adapted to a large range of sky apertures and telescope diameters. CODEX is designed to work as a seeing limited instrument. The requirements for the telescope are moderate and clearly identified.

We examine the possible reionization of the intergalactic medium (IGM) by the source UDF033238.7-274839.8 (hereafter HUDF-JD2), which was discovered in deep {\it HST}/VLT/{\it Spitzer} images obtained as part of the Great Observatory Origins Deep Survey and {\it Hubble} Ultra-Deep Field projects. Mobasher et al (2005) have identified HUDF-JD2 as a massive ($\sim6\times10^{11}M_\odot$) post-starburst galaxy at redshift z$\gtrsim6.5$. We find that HUDF-JD2 may be capable of reionizing its surrounding region of the Universe, starting the process at a redshift as high as z$\approx 15 \pm5$., Comment: 6 pages, 2 figures. Accepted for publication in ApJ Letters

Molecular absorption lines have become an important tool in studying the astrochemistry of the dense and cold interstellar medium in both our own Galaxy and high redshift systems. The sensitivity is to first order only dependent on the observed continuum flux. Apart from a few nearby galaxies, molecular absorption lines have been used to study the molecular ISM in 4 galaxies at redshifts 0.25-0.89. A large number of molecular species and transitions have been observed, allowing a detailed comparison with molecular gas in our own Galaxy. Planned instruments, such as ALMA, will allow studies of a larger number of molecular absorption line systems.

The colours of the galaxy class known as Extremely Red Objects (EROs; R-K>5) are considered to be consistent with two distinct galaxy populations at high redshift: evolved ellipticals or young dusty starbursts. In this paper the properties of EROs, spanned by the five photometric bands RIJHK, are investigated as to the possibility to distinguish between these two galaxy populations using only broad band photometry. The broad band colours of elliptical and starburst galaxies at redshifts up to 5 are computed from synthetic spectra obtained using the spectral evolution synthesis programme PEGASE.2. Two initial mass functions and a range of metallicities and extinctions are used. In order to be extremely red in the redshift range considered, the evolution of the R-K colour sets the requirement that ellipticals have to be less than 7-8 Gyr old, and that the starbursts must have colour excesses of E(B-V)>1, as derived from the nebular emission lines. In investigating the overlap in the different colour-colour planes as a function of redshift, it is found that the planes formed from permutations of the same three filters exhibit very similar overlap characteristics. In colour-colour planes formed within such triplets one of the filters will serve as a "pivot" band against which the two other bands are compared. The configuration where this pivot band lies between the other two bands has the best performance as a discriminator among the three possible configurations. A consistent behaviour cannot be found among the configurations formed by permuting four filters. The minimal filter configuration R-H vs. H-K is found to be the very best discriminator, working as such up to redshift 2.9., 12 pages, 8 figures, accepted for publication in A&A

A method for using the submillimeter band to determine photometric redshifts of luminous, high-z, dusty galaxies is presented. It is based on the observation that local ultraluminous infrared galaxies (ULIRGs) show an average spectral energy distribution (SED) that has a remarkably small dispersion for wavelengths λ > 50 μm. The shape of the long-wavelength part is independent of whether the local ULIRG possesses an active galactic nucleus or not. A local template is derived from a sample of ULIRG data presented by Klaas et al. in 2001. Using this template and the internal dispersion in its shape, it is shown that observations at two fixed submillimeter wavelengths, e.g., 450 and 850 μm, can be used to determine the photometric redshift of galaxies in the redshift range 1 < z < 5. The uncertainty in the redshift arising from the template SED amounts to Δz/z ~ 0.3, with an improvement at the higher redshift range. Implications for using this method together with the large instantaneous bandwidth of the Atacama Large Millimeter Array (ALMA) for deriving spectroscopic redshifts using CO emission is discussed.

For the first time, a search has been conducted in our Galaxy for the 119 GHz transition connecting to the ground state of O2, using the Odin satellite. Equipped with a sensitive 3 mm receiver (Tsy ...

We have compared two samples of galaxies in very high and low density environments in order to study their physical properties and stablish any possible relation among them. This paper focus on the CO content as a diagnostic tool to examine galaxy properties such as the amount of molecular gas and the star formation efficiency. The similarities in star formation efficiency of the dense environments and the field galaxies suggest that the physical processes controling the formation of stars from the molecular gas are local rather than global.

In order to study whether there is any correlation between nuclear activities, gas content, and the environment where galaxies reside, we have obtained optical and millimetric spectra for a well-defined sample of intermediate Hubble type spirals in dense environments and in the field. We found that these spirals in dense environments have on average: less molecular gas per blue luminosity, higher atomic gas fraction, lower current star formation rate, and the same star formation efficiency as field galaxies. Although none of these results stand out as a single strong diagnostic, given their statistical significance, taken together they indicate a trend for diminished gas content and star formation activity in galaxies in high density environments. Our results suggest that galaxies in dense environments have either (i) consumed their molecular gas via star formation in the past or (ii) that dense environments leads to an inhibition of molecular gas from atomic phase. The similarities in star formation efficiency of the dense environments and field galaxies suggest that the physical processes controling the formation of stars from the molecular gas are local rather than global. We also found that star formation rate per blue luminosity increases linearly as the total amount of gas increases in LINERs. This result, based on a small sample, suggests that LINERs are powered by star formation rather than an AGN., Comment: 12 pages, 12 figures, A&A accepted

We use data taken as part of HST/WFC3 observations of the Cosmic Assembly Near-infrared Deep Extragalactic Legacy Survey (CANDELS) to identify massive and evolved galaxies at 3, Comment: 15 pages, 14 figures, accepted to the ApJ

We report optical VLT FORS2 spectroscopy of the two Ly-alpha emitters (LAEs) companions to the quasi-stellar object (QSO) - sub-millimetre galaxy (SMG) system BRI1202-0725 at z = 4.7, which have recently been detected in the [CII]158um line by the Atacama Large Millimetre/Sub-millimetre Array (ALMA). We detect Ly-alpha emission from both sources and so confirm that these Ly-alpha emitter candidates are physically associated with the BRI1202- 0725 system. We also report the lack of detection of any high ionisation emission lines (N V, Si IV, C IV and He II) and find that these systems are likely not photoionised by the quasar, leaving in situ star formation as the main powering source of these LAEs. We also find that both LAEs have Ly-alpha emission much broader (1300 km/s) than the [CII] emission and broader than most LAEs. In addition, both LAEs have roughly symmetric Ly-alpha profiles implying that both systems are within the HII sphere produced by the quasar. This is the first time that the proximity zone of a quasar is probed by exploiting nearby Ly-alpha emitters. We discuss the observational properties of these galaxies in the context of recent galaxy formation models., 6 pages, 5 figures, accepted for publication in MNRAS

The formation of bars in disk galaxies is a tracer of the dynamical maturity of the population. Previous studies have found that the incidence of bars in disks decreases from the local Universe to z ~ 1, and by z > 1 simulations predict that bar features in dynamically mature disks should be extremely rare. Here we report the discovery of strong barred structures in massive disk galaxies at z ~ 1.5 in deep rest-frame optical images from CANDELS. From within a sample of 876 disk galaxies identified by visual classification in Galaxy Zoo, we identify 123 barred galaxies. Selecting a sub-sample within the same region of the evolving galaxy luminosity function (brighter than L*), we find that the bar fraction across the redshift range 0.5< z < 2 (f_bar = 10.7 +6.3 -3.5% after correcting for incompleteness) does not significantly evolve. We discuss the implications of this discovery in the context of existing simulations and our current understanding of the way disk galaxies have evolved over the last 11 billion years., 11 pages, 6 figures; accepted for publication in MNRAS

We present the public release of the stellar mass catalogs for the GOODS-S and UDS fields obtained using some of the deepest near-IR images available, achieved as part of the Cosmic Assembly Near-infrared Deep Extragalactic Legacy Survey (CANDELS) project. We combine the effort from ten different teams, who computed the stellar masses using the same photometry and the same redshifts. Each team adopted their preferred fitting code, assumptions, priors, and parameter grid. The combination of results using the same underlying stellar isochrones reduces the systematics associated with the fitting code and other choices. Thanks to the availability of different estimates, we can test the effect of some specific parameters and assumptions on the stellar mass estimate. The choice of the stellar isochrone library turns out to have the largest effect on the galaxy stellar mass estimates, resulting in the largest distributions around the median value (with a semi interquartile range larger than 0.1 dex). On the other hand, for most galaxies, the stellar mass estimates are relatively insensitive to the different parameterizations of the star formation history. The inclusion of nebular emission in the model spectra does not have a significant impact for the majority of galaxies (less than a factor of 2 for ~80% of the sample). Nevertheless, the stellar mass for the subsample of young galaxies (age < 100 Myr), especially in particular redshift ranges (e.g., 2.2 < z < 2.4, 3.2 < z < 3.6, and 5.5 < z < 6.5), can be seriously overestimated (by up to a factor of 10 for < 20 Myr sources) if nebular contribution is ignored., Accepted for publication by ApJ. Replaced to match the final version (two tables and one figure added in the appendix)

We use GOODS and CANDELS images to identify progenitors of massive (log M > 10 Msun) compact "early-type" galaxies (ETGs) at z~1.6. Since merging and accretion increase the size of the stellar component of galaxies, if the progenitors are among known star-forming galaxies, these must be compact themselves. We select candidate progenitors among compact Lyman-break galaxies at z~3 based on their mass, SFR and central stellar density and find that these account for a large fraction of, and possibly all, compact ETGs at z~1.6. We find that the average far-UV SED of the candidates is redder than that of the non-candidates, but the optical and mid-IR SED are the same, implying that the redder UV of the candidates is inconsistent with larger dust obscuration, and consistent with more evolved (aging) star-formation. This is in line with other evidence that compactness is a sensitive predictor of passivity among high-redshift massive galaxies. We also find that the light distribution of both the compact ETGs and their candidate progenitors does not show any extended "halos" surrounding the compact "core", both in individual images and in stacks. We argue that this is generally inconsistent with the morphology of merger remnants, even if gas-rich, as predicted by N-body simulations. This suggests that the compact ETGs formed via highly dissipative, mostly gaseous accretion of units whose stellar components are very small and undetected in the HST images, with their stellar mass assembling in-situ, and that they have not experienced any major merging until the epoch of observations at z~1.6., 25 pages, 20 figures; Accepted for publication in ApJ

QSO absorption spectra provide an extremely useful probe of possible cosmological variation in various physical constants. Comparison of H I 21cm absorption with corresponding molecular (rotational) absorption spectra allows us to constrain variation in y=alpha^2*g_p where alpha is the fine structure constant and g_p is the proton g-factor. We analyse spectra of two QSOs, PKS 1413+135 and TXS 0218+357, and derive values of dy/y at absorption redshifts of z=0.2467 and 0.6847 by simultaneous fitting of the H I 21cm and molecular lines. We find dy/y=(-0.20 +/- 0.44)*10^{-5} and dy/y=(-0.16 +/- 0.54)*10^{-5} respectively, indicating an insignificantly smaller y in the past. We compare our results with other recent constraints from the same two QSOs (Drinkwater et al. 1998; Carilli et al. 2000) and with our recent optical constraints which indicated a smaller alpha at higher redshifts., Comment: 6 Pages, 3 Figures, Accepted to MNRAS, small changes after referee's comments, accepted version

The prime goal of this work is to compare the properties of galaxies in dense environments and in the field and to study whether there is any correlation between nuclear activities (star-formation and AGN), the H2 mass and the environment where galaxies reside.

We detected with the IRAM interferometer the lines of CO(4-3) and CO(9-8) from the recently-discovered broad absorption line quasar APM 08279+5255. The molecular lines are at a redshift of 3.911, which we take to be the true cosmological redshift of the quasar's host galaxy. This means the quasar emission lines at z=3.87 are blueshifted by a kinematic component of -2500 km/s, and, along with the broad absorption lines, are probably emitted in the quasar's wind or jet, moving toward us. The CO line ratios suggest the molecular gas is at a temperature of about 200 K, at a density of about 4000 cm^-3. We also detected the dust emission at 94 and 214 GHz (emitted wavelengths 650 and 290 microns). The spectral index of the mm/submm continuum is +3.2, indicating the dust emission is optically thin in this part of the spectrum. The extremely high CO and dust luminosities suggest magnification by gravitational lensing. Using the optical extent and our limit on the size of the CO region, we estimate a magnification of 7 to 30 for the CO lines and the far-IR continuum, and 14 to 60 for the optical/UV. In this interpretation, the molecular gas and dust is in a nuclear disk of radius 90 to 270 pc around the quasar. The quasar is 25 to 100 times stronger than, but otherwise resembles, the nucleus of Mrk 231.

Resume L'absorption par les molecules du rayonnement millimetrique des quasars est un nouvel outil permettant de sonder le ga/ froid a tres grande distance, en beneficiant de tres haute resolution angulaire ( ≈ 10−3) et spectrale (30 m/s). Jusqu'a present, nous avons decouvert quatre systemes d'absorption et jusqu'a 20 raies moleculaires ont ete detectees dans un seul objet (HCO+, HNC, HCN, N2H+, C18O, CS, H2CO, CN. etc). Les abondances moleculaires, les temperatures d'excitation peuvent etre etudiees en detail dans ces galaxies lointaines. Les densites de colonne echantillonnees par cette technique sont comprises entre N(H2) = 1020 et 1024 cm−2. Les composantes diffuses permettent d'obtenir une limite superieure de la temperature du corps noir cosmique, en fonction de l'âge de l'Univers. L'existence de raies millimetriques en absorption necessite d'avoir le centre d'une galaxie sur la ligne de visee d'un quasar, ce qui implique la presence d'images gravitationnelles. C'est pourquoi ces mesures contribuent a la determination des parametres cosmologiques. H0 et q0.

We present results from the Cosmic Assembly Near-infrared Deep Extragalactic Legacy Survey (CANDELS) photometric redshift methods investigation. In this investigation, the results from eleven participants, each using a different combination of photometric redshift code, template spectral energy distributions (SEDs) and priors, are used to examine the properties of photometric redshifts applied to deep fields with broad-band multi-wavelength coverage. The photometry used includes U-band through mid-infrared filters and was derived using the TFIT method. Comparing the results, we find that there is no particular code or set of template SEDs that results in significantly better photometric redshifts compared to others. However, we find codes producing the lowest scatter and outlier fraction utilize a training sample to optimize photometric redshifts by adding zero-point offsets, template adjusting or adding extra smoothing errors. These results therefore stress the importance of the training procedure. We find a strong dependence of the photometric redshift accuracy on the signal-to-noise ratio of the photometry. On the other hand, we find a weak dependence of the photometric redshift scatter with redshift and galaxy color. We find that most photometric redshift codes quote redshift errors (e.g., 68% confidence intervals) that are too small compared to that expected from the spectroscopic control sample. We find that all codes show a statistically significant bias in the photometric redshifts. However, the bias is in all cases smaller than the scatter, the latter therefore dominates the errors. Finally, we find that combining results from multiple codes significantly decreases the photometric redshift scatter and outlier fraction. We discuss different ways of combining data to produce accurate photometric redshifts and error estimates., 26 pages, 15 figures, ApJ in press

We present a kinematic analysis of the dense molecular gas in the central 200 parsecs of the nearby galaxy NGC1097, based on Cycle 0 observations with the Atacama Large Millimeter/sub-millimeter Array (ALMA). We use the HCN(4-3) line to trace the densest interstellar molecular gas, and quantify its kinematics, and estimate an inflow rate for the molecular gas. We find a striking similarity between the ALMA kinematic data and the analytic spiral inflow model that we have previously constructed based on ionized gas velocity fields on larger scales. We are able to follow dense gas streaming down to 40 pc distance from the supermassive black hole in this Seyfert 1 galaxy. In order to fulfill marginal stability, we deduce that the dense gas is confined to a very thin disc, and we derive a dense gas inflow rate of 0.09 Msun/yr at 40 pc radius. Combined with previous values from the Ha and CO gas, we calculate a combined molecular and ionized gas inflow rate of 0.2 Msun/yr at 40 pc distance from the central supermassive black hole of NGC1097., Accepted for Publication in the ApJ Letters

Using deep 100-160 micron observations in GOODS-S from the GOODS-H survey, combined with HST/WFC3 NIR imaging from CANDELS, we present the first morphological analysis of a complete, FIR selected sample of 52 ULIRGs at z~2. We also make use of a comparison sample of galaxies without Herschel detections but with the same z and magnitude distribution. Our visual classifications of these two samples indicate that the fraction of objects with disk and spheroid morphologies is roughly the same but that there are significantly more mergers, interactions, and irregular galaxies among the ULIRGs. The combination of disk and irregular/interacting morphologies suggests that early stage interactions and minor mergers could play an important role in ULIRGs at z~2. We compare these fractions with those of a z~1 sample across a wide luminosity range and find that the fraction of disks decreases systematically with L_IR while the fraction of mergers and interactions increases, as has been observed locally. At comparable luminosities, the fraction of ULIRGs with various morphological classifications is similar at z~2 and z~1. We investigate the position of the ULIRGs, along with 70 LIRGs, on the specific star formation rate versus redshift plane, and find 52 systems to be starbursts (lie more than a factor of 3 above the main sequence relation). The morphologies of starbursts are dominated by interacting and merging systems (50%). If irregular disks are included as potential minor mergers, then we find that up to 73% of starbursts are involved in a merger or interaction at some level. Although the final coalescence of a major merger may not be required for the high luminosities of ULIRGs at z~2 as is the case locally, the large fraction of interactions at all stages and potential minor mergers suggest that the high star formation rates of ULIRGs are still largely externally triggered at z~2., 16 pages, 12 figures - Accepted for publication in the Astrophysical Journal

The Cosmic Assembly Near-infrared Deep Extragalactic Legacy Survey (CANDELS) is designed to document the first third of galactic evolution, over the approximate redshift (z) range 8--1.5. It will image >250,000 distant galaxies using three separate cameras on the Hubble Space Telescope, from the mid-ultraviolet to the near-infrared, and will find and measure Type Ia supernovae at z>1.5 to test their accuracy as standardizable candles for cosmology. Five premier multi-wavelength sky regions are selected, each with extensive ancillary data. The use of five widely separated fields mitigates cosmic variance and yields statistically robust and complete samples of galaxies down to a stellar mass of 10^9 M_\odot to z \approx 2, reaching the knee of the ultraviolet luminosity function (UVLF) of galaxies to z \approx 8. The survey covers approximately 800 arcmin^2 and is divided into two parts. The CANDELS/Deep survey (5\sigma\ point-source limit H=27.7 mag) covers \sim 125 arcmin^2 within GOODS-N and GOODS-S. The CANDELS/Wide survey includes GOODS and three additional fields (EGS, COSMOS, and UDS) and covers the full area to a 5\sigma\ point-source limit of H \gtrsim 27.0 mag. Together with the Hubble Ultra Deep Fields, the strategy creates a three-tiered "wedding cake" approach that has proven efficient for extragalactic surveys. Data from the survey are nonproprietary and are useful for a wide variety of science investigations. In this paper, we describe the basic motivations for the survey, the CANDELS team science goals and the resulting observational requirements, the field selection and geometry, and the observing design. The Hubble data processing and products are described in a companion paper., Comment: Submitted to Astrophysical Journal Supplement Series; Revised version, subsequent to referee report

We explore methods to improve the estimates of star formation rates and mean stellar population ages from broadband photometry of high redshift star-forming galaxies. We use synthetic spectral templates with a variety of simple parametric star formation histories to fit broadband spectral energy distributions. These parametric models are used to infer ages, star formation rates and stellar masses for a mock data set drawn from a hierarchical semi-analytic model of galaxy evolution. Traditional parametric models generally assume an exponentially declining rate of star-formation after an initial instantaneous rise. Our results show that star formation histories with a much more gradual rise in the star formation rate are likely to be better templates, and are likely to give better overall estimates of the age distribution and star formation rate distribution of Lyman break galaxies. For B- and V-dropouts, we find the best simple parametric model to be one where the star formation rate increases linearly with time. The exponentially-declining model overpredicts the age by 100 % and 120 % for B- and V-dropouts, on average, while for a linearly-increasing model, the age is overpredicted by 9 % and 16 %, respectively. Similarly, the exponential model underpredicts star-formation rates by 56 % and 60 %, while the linearly-increasing model underpredicts by 15 % 22 %, respectively. For U-dropouts, the models where the star-formation rate has a peak (near z ~ 3) provide the best match for age -- overprediction is reduced from 110 % to 26 % -- and star-formation rate -- underprediction is reduced from 58 % to 22 %. We classify different types of star-formation histories in the semi-analytic models and show how the biases behave for the different classes. We also provide two-band calibration formulae for stellar mass and star formation rate estimations., 28 pages, 7 figures, minor changes; published in ApJ

We present a new technique for identifying massive and evolved galaxies at z∼5. The technique is based on broad-band deep photometry, using the strength of Balmer Break features, which is shifted between the K-band and m 3.6 wavelengths at this redshift. The main criterion we use to identify these galaxies is therefore the K–m 3.6 colors. We found a total of 11 galaxies in the GOODS-S field at z∼5, with stellar masses between 1010 and 5×1011 M⊙ and ages >100 Myr. The existence of such a population of galaxies strongly constrains current galaxy formation scenarios. The implications of this population for formation of galaxies is discussed.

We discuss the use of population synthesis models as a mean of selecting galaxies based on age/stellar mass. In particular, we apply SED fitting on a sample from the GOODS-S field.

We present the results of a z>2.9 survey for HI 21-cm and molecular absorption in the hosts of radio quasars using the GMRT and the Tidbinbilla 70-m telescope. Previously published searches, which are overwhelmingly at redshifts of z2.5. We therefore believe that our high redshift selection is responsible for our exclusive non-detections, and find that at ultra-violet luminosities of >10e23 W/Hz, 21-cm absorption has never been detected. We also find this to not only apply to our targets, but also those at low redshift exhibiting similar luminosities, giving zero detections out of a total of 16 sources over z=0.24 to 3.8. This is in contrast to the < 10e23 W/Hz sources where there is a near 50% detection rate of 21-cm absorption. The mix of 21-cm detections and non-detections is currently attributed to orientation effects, where according to unified schemes of active galactic nuclei, 21-cm absorption is more likely to occur in sources designated as radio galaxies (type-2 objects, where the nucleus is viewed through dense obscuring circumnuclear gas) than in quasars(type-1 objects, where we have a direct view to the nucleus). However, due to the exclusively high ultra-violet luminosities of our targets it is not clear whether orientation effects alone can wholly account for the distribution, although there exists the possibility that the large luminosities are indicative of a changing demographic of galaxy types. We also find that below luminosities of ~10e23 W/Hz, both type-1 and type-2 objects have a 50% likelihood of exhibiting 21-cm absorption., Comment: 21 pages, accepted by MNRAS

The redshifts of all cosmologically distant sources are expected to experience a small, systematic drift as a function of time due to the evolution of the Universe's expansion rate. A measurement of this effect would represent a direct and entirely model-independent determination of the expansion history of the Universe over a redshift range that is inaccessible to other methods. Here we investigate the impact of the next generation of Extremely Large Telescopes on the feasibility of detecting and characterising the cosmological redshift drift. We consider the Lyman alpha forest in the redshift range 2 < z < 5 and other absorption lines in the spectra of high redshift QSOs as the most suitable targets for a redshift drift experiment. Assuming photon-noise limited observations and using extensive Monte Carlo simulations we determine the accuracy to which the redshift drift can be measured from the Ly alpha forest as a function of signal-to-noise and redshift. Based on this relation and using the brightness and redshift distributions of known QSOs we find that a 42-m telescope is capable of unambiguously detecting the redshift drift over a period of ~20 yr using 4000 h of observing time. Such an experiment would provide independent evidence for the existence of dark energy without assuming spatial flatness, using any other cosmological constraints or making any other astrophysical assumption., Accepted for publication in MNRAS, 27 pages, 19 figures