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Register a new userHELP: A catalogue of 170 million objects, selected at 0.36-4.5 $mu$m, from 1270 deg.$^{2}$ of prime extragalactic fields
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We present an optical to near-infrared selected astronomical catalogue covering 1270 deg.$^2$. This is the first attempt to systematically combine data from 23 of the premier extragalactic survey fields - the product of a vast investment of telescope time. The fields are those imaged by the Herschel Space Observatory which form the Herschel Extragalactic Legacy Project (HELP). Our catalogue of 170 million objects is constructed by a positional cross match of 51 public surveys. This high resolution optical, near-infrared, and mid-infrared catalogue is designed for photometric redshift estimation, extraction of fluxes in lower resolution far-infrared maps, and spectral energy distribution modelling. It collates, standardises, and provides value added derived quantities including corrected aperture magnitudes and astrometry correction over the Herschel extragalactic wide fields for the first time. $grizy$ fluxes are available on all fields with $g$ band data reaching $5sigma$ point-source depths in a 2 arcsec aperture of 23.5, 24.4, and 24.6 (AB) mag at the 25th, 50th, and 75th percentiles, by area covered, across all HELP fields. It has $K$ or $K_s$ coverage over 1146 deg.$^2$ with depth percentiles of 20.2, 20.4, and 21.0 mag respectively. The IRAC Ch 1 band is available over 273 deg.$^2$ with depth percentiles of 17.7, 21.4, and 22.2 mag respectively. This paper defines the masterlist objects for the first data release (DR1) of HELP. This large sample of standardised total and corrected aperture fluxes, uniform quality flags, and completeness measures provides large well understood statistical samples over the full Herschel extragalactic sky.
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Aims. We observe occultations of WASP-24b to measure brightness temperatures and to determine whether or not its atmosphere exhibits a thermal inversion (stratosphere). Methods. We observed occultations of WASP-24b at 3.6 and 4.5 {mu}m using the Spitzer Space Telescope. It has been suggested that there is a correlation between stellar activity and the presence of
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The W-CDF-S and ELAIS-S1 fields will be two of the LSST Deep Drilling fields, but the availability of spectroscopic redshifts within these two fields is still limited on deg^2 scales. To prepare for future science, we use EAZY to estimate photometric redshifts (photo-zs) in these two fields based on forced-photometry catalogs. Our photo-z catalog consists of ~0.8 million sources covering 4.9 deg^2 in W-CDF-S and ~0.8 million sources covering 3.4 deg^2 in ELAIS-S1, among which there are ~0.6 (W-CDF-S) and ~0.4 (ELAIS-S1) million sources having signal-to-noise-ratio (SNR) > 5 detections in more than 5 bands. By comparing photo-zs and available spectroscopic redshifts, we demonstrate the general reliability of our photo-z measurements. Our photo-z catalog is publicly available at doi{10.5281/zenodo.4603178}.
Using data from the Infrared Array Camera on the Spitzer Space Telescope, we present photometric observations of a sample of 100 trans-Neptunian objects (TNOs) beyond 2.2 {mu}m. These observations, collected with two broad-band filters centered at 3.6 and 4.5 {mu}m, were done in order to study the surface composition of TNOs, which are too faint to obtain spectroscopic measurements. With this aim, we have developed a method for the identification of different materials that are found on the surfaces of TNOs. In our sample, we detected objects with colors that are consistent with the presence of small amounts of water and were able to distinguish between surfaces that are predominately composed of complex organics and amorphous silicates. We found that 86% of our sample have characteristics that are consistent with a certain amount of water ice, and the most common composition (73% of the objects) is a mixture of water ice, amorphous silicates, and complex organics. 23% of our sample may include other ices such as carbon monoxide, carbon dioxide, methane or methanol. Additionally, only small objects seem to have surfaces dominated by silicates. This method is a unique tool for the identification of complex organics and to obtain the surface composition of extremely faint objects. Also, this method will be beneficial when using the James Webb Space Telescope for differentiating groups within the trans-Neptunian population.
We present a method of selection of 24~$mu$m galaxies from the AKARI North Ecliptic Pole (NEP) Deep Field down to $150 mbox{ }mu$Jy and measurements of their two-point correlation function. We aim to associate various 24 $mu$m selected galaxy populations with present day galaxies and to investigate the impact of their environment on the direction of their subsequent evolution. We discuss using of Support Vector Machines (SVM) algorithm applied to infrared photometric data to perform star-galaxy separation, in which we achieve an accuracy higher than 80%. The photometric redshift information, obtained through the CIGALE code, is used to explore the redshift dependence of the correlation function parameter ($r_{0}$) as well as the linear bias evolution. This parameter relates galaxy distribution to the one of the underlying dark matter. We connect the investigated sources to their potential local descendants through a simplified model of the clustering evolution without interactions. We observe two different populations of star-forming galaxies, at $z_{med}sim 0.25$, $z_{med}sim 0.9$. Measurements of total infrared luminosities ($L_{TIR}$) show that the sample at $z_{med}sim 0.25$ is composed mostly of local star-forming galaxies, while the sample at $z_{med}sim0.9$ is composed of luminous infrared galaxies (LIRGs) with $L_{TIR}sim 10^{11.62}L_{odot}$. We find that dark halo mass is not necessarily correlated with the $L_{TIR}$: for subsamples with $L_{TIR}= 10^{11.15} L_{odot}$ at $z_{med}sim 0.7$ we observe a higher clustering length ($r_{0}=6.21pm0.78$ $[h^{-1} mbox{Mpc}]$) than for a subsample with mean $L_{TIR}=10^{11.84} L_{odot}$ at $z_{med}sim1.1$ ($r_{0}=5.86pm0.69$ $h^{-1} mbox{Mpc}$). We find that galaxies at $z_{med}sim 0.9$ can be ancestors of present day $L_{*}$ early type galaxies, which exhibit a very high $r_{0}sim 8$~$h^{-1} mbox{Mpc}$.
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