arXiv subjects

T. H. Jarrett

Publications and source records attributed to T. H. Jarrett.

At least 55 records · Page 3Linked to original sources

arXiv2018

A Multi-Scale Study of Star Formation in Messier 33

For the Local Group Scd galaxy M 33 this paper presents a multi-scale study of the relationship between the monochromatic star formation rate (SFR) estimator based on 12 $μ$m emission and the total SFR estimator based on a combination of far-ultraviolet and 24 $μ$m emission. We show the 12 $μ$m emission to be a linear estimator of total SFR on spatial scales from 782 pc down to 49 pc, over almost four magnitudes in SFR. These results therefore extend to sub-kpc length scales the analogous results from other studies for global length scales. We use high-resolution HI and $^{12}\mathrm{CO}(J=2-1)$ image sets from the literature to compare the star formation to the neutral gas. For the full range of length scales we find well-defined power-law relationships between 12 $μ$m-derived SFR surface densities and neutral gas surface densities. For the H$_\mathrm{2}$ gas component almost all correlations are consistent with being linear. No evidence is found for a breakdown in the star formation law at small length scales in M 33 reported by other authors. We show that the average star formation efficiency in M 33 is roughly $10^{-9}$ yr$^{-1}$ and that it remains constant down to giant molecular cloud length scales. Toomre and shear-based models of the star formation threshold are shown to inaccurately account for the star formation activity in the inner disc of M 33. Finally, we clearly show that the HI saturation limit of $\approx 9$ M$_{\odot}$ pc$^{-2}$ reported in the literature for other galaxies is not an intrinsic property of M 33 - it is systematically introduced as an artefact of spatially smoothing the data.

astro-ph.GA↗

arXiv2018

The 2.4 $μ$m Galaxy Luminosity Function as Measured Using WISE. III. Measurement Results

The WISE satellite surveyed the entire sky multiple times in four infrared wavelengths (3.4, 4.6, 12, and $22\,μ$m; Wright et al. 2010). The unprecedented combination of coverage area and depth gives us the opportunity to measure the luminosity function of galaxies, one of the fundamental quantities in the study of them, at $2.4\ μ$m to an unparalleled level of formal statistical accuracy in the near infrared. The big advantage of measuring luminosity functions at wavelengths in the window $\approx 2$ to $3.5\,μ$m is that it correlates more closely to the total stellar mass in galaxies than others. In this paper we report on the parameters for the $2.4\,μ$m luminosity function of galaxies obtained from applying the spectroluminosity functional based methods defined in Lake et al. (2017b) to the data sets described in Lake et al. (2017a) using the mean and covariance of $2.4\,μ$m normalized SEDs from Lake & Wright (2016). In terms of single Schechter function parameters evaluated at the present epoch, the combined result is: $ϕ_\star = 5.8 \pm [0.3_{\mathrm{stat}},\, 0.3_{\mathrm{sys}}] \times 10^{-3} \operatorname{Mpc}^{-3}$, $L_\star = 6.4 \pm [0.1_{\mathrm{stat}},\, 0.3_{\mathrm{sys}}] \times 10^{10}\, L_{2.4\,μ\mathrm{m}\,\odot}$ ($M_\star = -21.67 \pm [0.02_{\mathrm{stat}},\, 0.05_{\mathrm{sys}}]\operatorname{AB\ mag}$), and $α= -1.050 \pm [0.004_{\mathrm{stat}},\, 0.03_{\mathrm{sys}}]$, corresponding to a galaxy number density of $0.08\operatorname{Mpc}^{-3}$ brighter than $10^6\, L_{2.4\,μ\mathrm{m}\,\odot}$ ($10^{-3} \operatorname{Mpc}^{-3}$ brighter than $L_\star$) and a $2.4\,μ$m luminosity density equivalent to $3.8\times10^{8}\,L_{2.4\,μ\mathrm{m}\,\odot}\operatorname{Mpc}^{-3}$. $\ldots$

astro-ph.GA↗

arXiv2018

The 2.4 $μ$m Galaxy Luminosity Function as Measured Using WISE. II. Sample Selection

The WISE satellite surveyed the entire sky multiple times in four infrared (IR) wavelengths ($3.4,\ 4.6,\ 12,$ and $22\, μ$m, Wright et al. 2010). This all-sky IR photometric survey makes it possible to leverage many of the large publicly available spectroscopic redshift surveys to measure galaxy properties in the IR. While characterizing the cross-matching of WISE data to a single survey is a straightforward process, doing it with six different redshift surveys takes a fair amount of space to characterize adequately, because each survey has unique caveats and characteristics that need addressing. This work describes a data set that results from matching five public redshift surveys with the AllWISE data release, along with a reanalysis of the data described in Lake et al. 2012. The combined data set has an additional flux limit of $80\,μ$Jy ($19.14$ AB mag) in WISE's W1 filter imposed in order to limit it to targets with high completeness and reliable photometry in the AllWISE data set. Consistent analysis of all of the data is only possible if the color bias discussed in Ilbert et al. (2004) is addressed (for example: the techniques explored in the first paper in this series Lake et al. 2017b). The sample defined herein is used in this paper's sequel paper, Lake et al. 2017a), to measure the luminosity function of galaxies at $2.4\, μ$m rest frame wavelength, and the selection process of the sample is optimized for this purpose.

astro-ph.GA↗

arXiv2018

A GBT Survey of the HALOGAS Galaxies and Their Environments I: Revealing the full extent of HI around NGC891, NGC925, NGC4414 & NGC4565

We present initial results from a deep neutral hydrogen (HI) survey of the HALOGAS galaxy sample, which includes the spiral galaxies NGC891, NGC925, NGC4414, and NGC4565, performed with the Robert C. Byrd Green Bank Telescope (GBT). The resulting observations cover at least four deg$^2$ around these galaxies with an average 5$σ$ detection limit of 1.2$\times$10$^{18}$ cm$^{-2}$ over a velocity range of 20 km s$^{-1}$ and angular scale of 9.1$'$. In addition to detecting the same total flux as the GBT data, the spatial distribution of the GBT and original Westerbork Synthesis Radio Telescope (WSRT) data match well at equal spatial resolutions. The HI mass fraction below HI column densities of 10$^{19}$ cm$^{-2}$ is, on average, 2\%. We discuss the possible origins of low column density HI of nearby spiral galaxies. The absence of a considerable amount of newly detected HI by the GBT indicates these galaxies do not have significant extended diffuse HI structures, and suggests future surveys planned with the SKA and its precursors must go \textit{at least} as deep as 10$^{17}$ cm$^{-2}$ in column density to significantly increase the probability of detecting HI associated with the cosmic web and/or cold mode accretion.

astro-ph.GA↗

arXiv2018

Relationships between HI Gas Mass, Stellar Mass and Star Formation Rate of HICAT+WISE (HI-WISE) Galaxies

We have measured the relationships between HI mass, stellar mass and star formation rate using the HI Parkes All Sky-Survey Catalogue (HICAT) and the Wide-field Infrared Survey Explorer (WISE). Of the 3,513 HICAT sources, we find 3.4 micron counterparts for 2,896 sources (80%) and provide new WISE matched aperture photometry for these galaxies. For our principal sample of spiral galaxies with W1 $\le$ 10 mag and z $\le$ 0.01, we identify HI detections for 93% of the sample. We measure lower HI-stellar mass relationships that HI selected samples that do not include spiral galaxies with little HI gas. Our observations of the spiral sample show that HI mass increases with stellar mass with a power-law index 0.35; however, this value is dependent on T-type, which affects both the median and the dispersion of HI mass. We also observe an upper limit on the HI gas fraction, which is consistent with a halo spin parameter model. We measure the star formation efficiency of spiral galaxies to be constant 10$^{-9.57}$ yr$^{-1}$ $\pm$ 0.4 dex for 2.5 orders of magnitude in stellar mass, despite the higher stellar mass spiral showing evidence of quenched star formation.

astro-ph.GA↗

arXiv2018

After The Fall: The Dust and Gas in E+A Post-Starburst Galaxies

The traditional picture of post-starburst galaxies as dust- and gas-poor merger remnants, rapidly transitioning to quiescence, has been recently challenged. Unexpected detections of a significant ISM in many post-starbursts raise important questions. Are they truly quiescent and, if so, what mechanisms inhibit further star formation? What processes dominate their ISM energetics? We present an infrared spectroscopic and photometric survey of 33 SDSS-selected E+A post-starbursts, aimed at resolving these questions. We find compact, warm dust reservoirs with high PAH abundances, and total gas and dust masses significantly higher than expected from stellar recycling alone. Both PAH/TIR and dust-to-burst stellar mass ratios are seen to decrease with post-burst age, indicative of the accumulating effects of dust destruction and an incipient transition to hot, early-type ISM properties. Their infrared spectral properties are unique, with dominant PAH emission, very weak nebular lines, unusually strong H$_{2}$ rotational emission, and deep ${\rm [C\, II]}$ deficits. There is substantial scatter among SFR indicators, and both PAH and TIR luminosities provide overestimates. Even as potential upper limits, all tracers show that the SFR has typically experienced a more than two order-of-magnitude decline since the starburst, and that the SFR is considerably lower than expected given both their stellar masses and molecular gas densities. These results paint a coherent picture of systems in which star formation was, indeed, rapidly truncated, but in which the ISM was $\textit{not}$ completely expelled, and is instead supported against collapse by latent or continued injection of turbulent or mechanical heating. The resulting aging burst populations provide a "high-soft" radiation field which seemingly dominates the E+As' unusual ISM energetics.

astro-ph.GA↗

arXiv2018

Calibrating Star Formation in WISE using Total Infrared Luminosity

We present accurate resolved $WISE$ photometry of galaxies in the combined SINGS and KINGFISH sample. The luminosities in the W3 12$μ$m and W4 23$μ$m bands are calibrated to star formation rates (SFRs) derived using the total infrared luminosity, avoiding UV/optical uncertainties due to dust extinction corrections. The W3 relation has a 1-$σ$ scatter of 0.15 dex over nearly 5 orders of magnitude in SFR and 12$μ$m luminosity, and a range in host stellar mass from dwarf (10$^7$ M$_\odot$) to $\sim3\times$M$_\star$ (10$^{11.5}$ M$_\odot$) galaxies. In the absence of deep silicate absorption features and powerful active galactic nuclei, we expect this to be a reliable SFR indicator chiefly due to the broad nature of the W3 band. By contrast the W4 SFR relation shows more scatter (1-$σ=$ 0.18 dex). Both relations show reasonable agreement with radio continuum-derived SFRs and excellent accordance with so-called "hybrid" H$α+ 24 μ$m and FUV$+$24$μ$m indicators. Moreover, the $WISE$ SFR relations appear to be insensitive to the metallicity range in the sample. We also compare our results with IRAS-selected luminous infrared galaxies, showing that the $WISE$ relations maintain concordance, but systematically deviate for the most extreme galaxies. Given the all-sky coverage of $WISE$ and the performance of the W3 band as a SFR indicator, the $L_{12μ\rm m}$ SFR relation could be of great use to studies of nearby galaxies and forthcoming large area surveys at optical and radio wavelengths.

astro-ph.GA↗

arXiv2018

Herschel Spectroscopy of the Taffy Galaxies (UGC 12914/12915 = VV 254): Enhanced [C II] emission in the collisionally-formed bridge

Using the PACS and SPIRE spectrometers on-board Herschel, we obtained observations of the Taffy galaxies (UGC 12914/12915) and bridge. The Taffy system is believed to be the result of a face-on collision between two gas-rich galaxies, in which the stellar disks passed through each other, but the gas was dispersed into a massive H I and molecular bridge between them. Emission is detected and mapped in both galaxies and the bridge in the [C II]157.7 $μ$m and [O I]63.2 $μ$m fine-structure lines. Additionally, SPIRE FTS spectroscopy detects the [C I] $^3$P$_2$$\rightarrow$$^3$P$_1$(809.3 GHz) and [C I] $^3$P$_1$$\rightarrow$$3$P$_0$(492.2 GHz) neutral carbon lines, and weakly detects high-J CO transitions in the bridge. These results indicate that the bridge is composed of a warm multi-phase medium consistent with shock and turbulent heating. Despite low star formation rates in the bridge, the [C II] emission appears to be enhanced, reaching [C II]/FIR ratios of 3.3% in parts of the bridge. Both the [C II] and [O I] lines show broad intrinsic multi-component profiles, similar to those seen in previous CO 1-0 and H I observations. The [C II] emission shares similar line profiles with both the double-peaked H I profiles and shares a high-velocity component with single-peaked CO profiles in the bridge, suggesting that the [C II] emission originates in both the neutral and molecular phases. We show that it is feasible that a combination of turbulently heated H$_2$ and high column-density H I, resulting from the galaxy collision, is responsible for the enhanced [C II] emission.

astro-ph.GA↗

arXiv2017

An Overview of the MHONGOOSE Survey: Observing Nearby Galaxies with MeerKAT

MHONGOOSE is a deep survey of the neutral hydrogen distribution in a representative sample of 30 nearby disk and dwarf galaxies with HI masses from 10^6 to ~10^{11} M_sun, and luminosities from M_R ~ -12 to M_R ~ -22. The sample is selected to uniformly cover the available range in log(M_HI). Our extremely deep observations, down to HI column density limits of well below 10^{18} cm^{-2} - or a few hundred times fainter than the typical HI disks in galaxies - will directly detect the effects of cold accretion from the intergalactic medium and the links with the cosmic web. These observations will be the first ever to probe the very low-column density neutral gas in galaxies at these high resolutions. Combination with data at other wavelengths, most of it already available, will enable accurate modelling of the properties and evolution of the mass components in these galaxies and link these with the effects of environment, dark matter distribution, and other fundamental properties such as halo mass and angular momentum. MHONGOOSE can already start addressing some of the SKA-1 science goals and will provide a comprehensive inventory of the processes driving the transformation and evolution of galaxies in the nearby universe at high resolution and over 5 orders of magnitude in column density. It will be a Nearby Galaxies Legacy Survey that will be unsurpassed until the advent of the SKA, and can serve as a highly visible, lasting statement of MeerKAT's capabilities.

astro-ph.GA↗

arXiv2017

WISE data as a photometric redshift indicator for radio AGN

We show that mid-infrared data from the all-sky WISE survey can be used as a robust photometric redshift indicator for powerful radio AGN, in the absence of other spectroscopic or multi-band photometric information. Our work is motivated by a desire to extend the well-known K-z relation for radio galaxies to the wavelength range covered by the all-sky WISE mid-infrared survey. Using the LARGESS radio spectroscopic sample as a training set, and the mid-infrared colour information to classify radio sources, we generate a set of redshift probability distributions for the hosts of high-excitation and low-excitation radio AGN. We test the method using spectroscopic data from several other radio AGN studies, and find good agreement between our WISE-based redshift estimates and published spectroscopic redshifts out to z ~ 1 for galaxies and z ~ 3-4 for radio-loud QSOs. Our chosen method is also compared against other classification methods and found to perform reliably. This technique is likely to be particularly useful in the analysis of upcoming large-area radio surveys with SKA pathfinder telescopes, and our code is publicly available. As a consistency check, we show that our WISE-based redshift estimates for sources in the 843 MHz SUMSS survey reproduce the redshift distribution seen in the CENSORS study up to z ~ 2. We also discuss two specific applications of our technique for current and upcoming radio surveys; an interpretation of large scale HI absorption surveys, and a determination of whether low-frequency peaked spectrum sources lie at high redshift.

astro-ph.IM↗

arXiv2017

Calibration of ultraviolet, mid-infrared and radio star formation rate indicators

We present calibrations for star formation rate indicators in the ultraviolet, mid-infrared and radio continuum bands, including one of the first direct calibrations of 150 MHz as a star formation rate indicator. Our calibrations utilize 66 nearby star forming galaxies with Balmer decrement corrected H-alpha luminosities, which span 5 orders of magnitude in star formation rate and have absolute magnitudes of -24<M_r<-12. Most of our photometry and spectrophotometry is measured from the same region of each galaxy, and our spectrophotometry has been validated with SDSS photometry, so our random and systematic errors are small relative to the intrinsic scatter seen in star formation rate indicator calibrations. We find WISE W4 (22.8 micron), Spitzer 24 micron and 1.4 GHz have tight correlations with Balmer decrement corrected H-alpha luminosity, with scatter of only 0.2 dex. Our calibrations are comparable to those from the prior literature for L* galaxies, but for dwarf galaxies our calibrations can give star formation rates that are far greater than those derived from much of the prior literature.

astro-ph.GA↗

arXiv2017

Towards a Full Census of the Obscure(d) Vela Supercluster using MeerKAT

Recent spectroscopic observations of a few thousand partially obscured galaxies in the Vela constellation revealed a massive overdensity on supercluster scales straddling the Galactic Equator (l $\sim$ 272.5deg) at $cz \sim 18000$km/s. It remained unrecognised because it is located just beyond the boundaries and volumes of systematic whole-sky redshift and peculiar velocity surveys - and is obscured by the Milky Way. The structure lies close to the apex where residual bulkflows suggest considerable mass excess. The uncovered Vela Supercluster (VSCL) conforms of a confluence of merging walls, but its core remains uncharted. At the thickest foreground dust column densities (|b| < 6 deg) galaxies are not visible and optical spectroscopy is not effective. This precludes a reliable estimate of the mass of VSCL, hence its effect on the cosmic flow field and the peculiar velocity of the Local Group. Only systematic HI-surveys can bridge that gap. We have run simulations and will present early-science observing scenarios with MeerKAT 32 (M32) to complete the census of this dynamically and cosmologically relevant supercluster. M32 has been put forward because this pilot project will also serve as precursor project for HI MeerKAT Large Survey Projects, like Fornax and Laduma. Our calculations have shown that a survey area of the fully obscured part of the supercluster, where the two walls cross and the potential core of the supercluster resides, can be achieved on reasonable time-scales (200 hrs) with M32.

astro-ph.GA↗

arXiv2017

Updated 34-Band Photometry for the SINGS/KINGFISH Samples of Nearby Galaxies

We present an update to the ultraviolet-to-radio database of global broadband photometry for the 79 nearby galaxies that comprise the union of the KINGFISH (Key Insights on Nearby Galaxies: A Far-Infrared Survey with Herschel) and SINGS (Spitzer Infrared Nearby Galaxies Survey) samples. The 34-band dataset presented here includes contributions from observational work carried out with a variety of facilities including GALEX, SDSS, PS, NOAO, 2MASS, WISE, Spitzer, Herschel, Planck, JCMT, and the VLA. Improvements of note include recalibrations of previously-published SINGS BVRcIc and KINGFISH far-infrared/submillimeter photometry. Similar to previous results in the literature, an excess of submillimeter emission above model predictions is seen primarily for low-metallicity dwarf/irregular galaxies. This 34-band photometric dataset for the combined KINGFISH$+$SINGS sample serves as an important multi-wavelength reference for the variety of galaxies observed at low redshift. A thorough analysis of the observed spectral energy distributions is carried out in a companion paper.

astro-ph.GA↗

arXiv2017

Galaxy and Mass Assembly (GAMA): Exploring the WISE Cosmic Web in G12

We present an analysis of the mid-infrared WISE sources seen within the equatorial GAMA G12 field, located in the North Galactic Cap. Our motivation is to study and characterize the behavior of WISE source populations in anticipation of the deep multi-wavelength surveys that will define the next decade, with the principal science goal of mapping the 3D large scale structures and determining the global physical attributes of the host galaxies. In combination with cosmological redshifts, we identify galaxies from their WISE W1 3.4um resolved emission, and by performing a star-galaxy separation using apparent magnitude, colors and statistical modeling of star-counts. The resultant galaxy catalog has ~590,000 sources in 60 deg^2, reaching a W1 5-sigma depth of 31 uJy. At the faint end, where redshifts are not available, we employ a luminosity function analysis to show that approximately 27% of all WISE extragalactic sources to a limit of 17.5 mag (31 uJy) are at high redshift, z > 1. The spatial distribution is investigated using two-point correlation functions and a 3D source density characterization at 5 Mpc and 20 Mpc scales. For angular distributions, we find brighter and more massive sources are strongly clustered relative to fainter and lower mass source; likewise, based on WISE colors, spheroidal galaxies have the strongest clustering, while late-type disk galaxies have the lowest clustering amplitudes. Along the radial direction, the strongest clustering is in the largest redshift shell, while the weakest is in the nearest redshift shell, consistent with the stellar mass and morphological type dependency results. In three dimensions, we find a number of distinct groupings, often bridged by filaments and super-structures. Using special visualization tools, we map these structures, exploring how clustering may play a role with stellar mass and galaxy type.

astro-ph.CO↗

arXiv2016

NIR Tully-Fisher in the Zone of Avoidance. -- III. Deep NIR catalogue of the HIZOA galaxies

We present a deep near-infrared (NIR) photometric catalogue of sources from the Parkes HI Zone of Avoidance (HIZOA) survey, which forms the basis for an investigation of the matter distribution in the Zone of Avoidance. Observations were conducted between 2006 and 2013 using the Infrared Survey Facility (IRSF), a 1.4-m telescope situated at the South African Astronomical Observatory site in Sutherland. The images cover all 1108 HIZOA detections and yield 915 galaxies. An additional 105 bright 2MASS galaxies in the southern ZOA were imaged with the IRSF, resulting in 129 galaxies. The average $K_s$-band seeing and sky background for the survey are 1.38 arcsec and 20.1 mag, respectively. The detection rate as a function of stellar density and dust extinction is found to depend mainly on the HI mass of the HI detected galaxies, which in principal correlates with the NIR brightness of the spiral galaxies. The measured isophotal magnitudes are of sufficient accuracy (errors $\sim$ 0.02 mag) to be used in a Tully-Fisher analysis. In the final NIR catalogue, 285 galaxies have both IRSF and 2MASS photometry (180 HIZOA plus 105 bright 2MASX galaxies). The $K_s$-band isophotal magnitudes presented in this paper agree, within the uncertainties, with those reported in the 2MASX catalogue. Another 30 galaxies, from the HIZOA northern extension, are also covered by UKIDSS Galactic Plane Survey (GPS) images, which are one magnitude deeper than our IRSF images. A modified version of our photometry pipeline was used to derive the photometric parameters of these UKIDSS galaxies. Good agreement was found between the respective $K_s$-band isophotal magnitudes. These comparisons confirm the robustness of the isophotal parameters and demonstrate that the IRSF images do not suffer from foreground contamination, after star removal, nor under-estimate the isophotal fluxes of ZoA galaxies.

astro-ph.GA↗

arXiv2016

The Herschel-ATLAS Data Release 1 Paper II: Multi-wavelength counterparts to submillimetre sources

This paper is the second in a pair of articles presenting data release 1 (DR1) of the Herschel Astrophysical Terahertz Large Area Survey (H-ATLAS), the largest single open-time key project carried out with the Herschel Space Observatory. The H-ATLAS is a wide-area imaging survey carried out in five photometric bands at 100, 160, 250, 350 and 500$μ$m covering a total area of 600deg$^2$. In this paper we describe the identification of optical counterparts to submillimetre sources in DR1, comprising an area of 161 deg$^2$ over three equatorial fields of roughly 12$^\circ$x4.5$^\circ$ centred at 9$^h$, 12$^h$ and 14.5$^h$ respectively. Of all the H-ATLAS fields, the equatorial regions benefit from the greatest overlap with current multi-wavelength surveys spanning ultraviolet (UV) to mid-infrared regimes, as well as extensive spectroscopic coverage. We use a likelihood-ratio technique to identify SDSS counterparts at r<22.4 for 250-$μ$m-selected sources detected at $\geq$ 4$σ$ ($\approx$28mJy). We find `reliable' counterparts (reliability R$\geq$0.8) for 44,835 sources (39 per cent), with an estimated completeness of 73.0 per cent and contamination rate of 4.7 per cent. Using redshifts and multi-wavelength photometry from GAMA and other public catalogues, we show that H-ATLAS-selected galaxies at $z<0.5$ span a wide range of optical colours, total infrared (IR) luminosities, and IR/UV ratios, with no strong disposition towards mid-IR-classified AGN in comparison with optical selection. The data described herein, together with all maps and catalogues described in the companion paper (Valiante et al. 2016), are available from the H-ATLAS website at www.h-atlas.org.

astro-ph.GA↗

arXiv2016

WISE x SuperCOSMOS photometric redshift catalog: 20 million galaxies over 3pi steradians

We cross-match the two currently largest all-sky photometric catalogs, mid-infrared WISE and SuperCOSMOS scans of UKST/POSS-II photographic plates, to obtain a new galaxy sample that covers 3pi steradians. In order to characterize and purify the extragalactic dataset, we use external GAMA and SDSS spectroscopic information to define quasar and star loci in multicolor space, aiding the removal of contamination from our extended-source catalog. After appropriate data cleaning we obtain a deep wide-angle galaxy sample that is approximately 95% pure and 90% complete at high Galactic latitudes. The catalog contains close to 20 million galaxies over almost 70% of the sky, outside the Zone of Avoidance and other confused regions, with a mean surface density of over 650 sources per square degree. Using multiwavelength information from two optical and two mid-IR photometric bands, we derive photometric redshifts for all the galaxies in the catalog, using the ANNz framework trained on the final GAMA-II spectroscopic data. Our sample has a median redshift of z_{med} = 0.2 but with a broad dN/dz reaching up to z>0.4. The photometric redshifts have a mean bias of |delta_z|~10^{-3}, normalized scatter of sigma_z = 0.033 and less than 3% outliers beyond 3sigma_z. Comparison with external datasets shows no significant variation of photo-z quality with sky position. Together with the overall statistics, we also provide a more detailed analysis of photometric redshift accuracy as a function of magnitudes and colors. The final catalog is appropriate for `all-sky' 3D cosmology to unprecedented depths, in particular through cross-correlations with other large-area surveys. It should also be useful for source pre-selection and identification in forthcoming surveys such as TAIPAN or WALLABY.

astro-ph.CO↗

arXiv2016

The WSRT ZoA Perseus-Pisces Filament wide-field HI imaging survey I. HI catalogue and atlas

We present results of a blind 21cm HI-line imaging survey of a galaxy overdensity located behind the Milky Way at $\ell,b$ $\approx$ 160 deg, 0.5 deg. The overdensity corresponds to a Zone-of-Avoidance crossing of the Perseus-Pisces Supercluster filament. Although it is known that this filament contains an X-ray galaxy cluster (3C129) hosting two strong radio galaxies, little is known about galaxies associated with this potentially rich cluster because of the high Galactic dust extinction. We mapped a sky area of $\sim$9.6 sq.deg using the Westerbork Synthesis Radio Telescope in a hexagonal mosaic of 35 pointings observed for 12 hours each, in the radial velocity range $cz = 2400 - 16600$ km/s. The survey has a sensitivity of 0.36 mJy/beam rms at a velocity resolution of 16.5 km/s. We detected 211 galaxies, 62% of which have a near-infrared counterpart in the UKIDSS Galactic Plane Survey. We present a catalogue of the HI properties and an HI atlas containing total intensity maps, position-velocity diagrams, global HI profiles and UKIDSS counterpart images. For the resolved galaxies we also present HI velocity fields and radial HI surface density profiles. A brief analysis of the structures outlined by these galaxies finds that 87 of them lie at the distance of the Perseus-Pisces Supercluster ($cz \sim 4000 - 8000$ km/s) and seem to form part of the 3C129 cluster. Further 72 detections trace an overdensity at a velocity of $cz \approx$ 10000 km/s and seem to coincide with a structure predicted from mass density reconstructions in the first 2MASS Redshift Survey.

astro-ph.GA↗