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تسجيل مستخدم جديدThe Hubble Legacy Fields (HLF-GOODS-S) v1.5 Data Products: Combining 2442 Orbits of GOODS-S/CDF-S Region ACS and WFC3/IR Images
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We have submitted to MAST the 1.5 version data release of the Hubble Legacy Fields (HLF) project covering a 25 x 25 arcmin area over the GOODS-S (ECDF-S) region from the HST archival program AR-13252. The release combines exposures from Hubbles two main cameras, the Advanced Camera for Surveys (ACS/WFC) and the Wide Field Camera 3 (WFC3/IR), taken over more than a decade between mid-2002 to the end of 2016. The HLF includes essentially all optical (ACS/WFC F435W, F606W, F775W, F814W and F850LP filters) and infrared (WFC3/ IR F098M, F105W, F125W, F140W and F160W filters) data taken by Hubble over the original CDF-S region including the GOODS-S, ERS, CANDELS and many other programs (31 in total). The data has been released at https://archive.stsci.edu/prepds/hlf/ as images with a common astrometric reference frame, with corresponding inverse variance weight maps. We provide one image per filter of WFC3/IR images at 60 mas per pixel resolution and two ACS/WFC images per filter, at both 30 and 60 mas per pixel. Since this comprehensive dataset combines data from 31 programs on the GOODS-S/CDF-S, the AR proposal identified the MAST products by the global name Hubble Legacy Field, with this region being identified by HLF-GOODS-S. This dataset complements that of the Frontier Fields program. The total incorporated in the HLF-GOODS-S is 5.8 Msec in 7211 exposures from 2442 orbits. This is ~70% of a HST full cycle!
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This manuscript describes the public release of the Hubble Legacy Fields (HLF) project photometric catalog for the extended GOODS-South region from the Hubble Space Telescope (HST) archival program AR-13252. The analysis is based on the version 2.0 H
LF data release that now includes all ultraviolet (UV) imaging, combining three major UV surveys. The HLF data combines over a decade worth of 7475 exposures taken in 2635 orbits totaling 6.3 Msec with the HST Advanced Camera for Surveys Wide Field Channel (ACS/WFC) and the Wide Field Camera 3 (WFC3) UVIS/IR Channels in the greater GOODS-S extragalactic field, covering all major observational efforts (e.g., GOODS, GEMS, CANDELS, ERS, UVUDF and many other programs; see Illingworth et al 2019, in prep). The HLF GOODS-S catalogs include photometry in 13 bandpasses from the UV (WFC3/UVIS F225W, F275W and F336W filters), optical (ACS/WFC F435W, F606W, F775W, F814W and F850LP filters), to near-infrared (WFC3/IR F098M, F105W, F125W, F140W and F160W filters). Such a data set makes it possible to construct the spectral energy distributions (SEDs) of objects over a wide wavelength range from high resolution mosaics that are largely contiguous. Here, we describe a photometric analysis of 186,474 objects in the HST imaging at wavelengths 0.2--1.6$mu$m. We detect objects from an ultra-deep image combining the PSF-homogenized and noise-equalized F850LP, F125W, F140W and F160W images, including Gaia astrometric corrections. SEDs were determined by carefully taking the effects of the point-spread function in each observation into account. All of the data presented herein are available through the HLF website (https://archive.stsci.edu/prepds/hlf/).
We analyze the >4-sigma sources in the most sensitive 100 arcmin^2 area (rms <0.56 mJy) of a SCUBA-2 850 micron survey of the GOODS-S and present the 75 band 7 ALMA sources (>4.5-sigma) obtained from high-resolution interferometric follow-up observat
ions. The SCUBA-2---and hence ALMA---samples should be complete to 2.25 mJy. Of the 53 SCUBA-2 sources in this complete sample, only five have no ALMA detections, while 13% (68% confidence range 7-19%) have multiple ALMA counterparts. Color-based high-redshift dusty galaxy selection techniques find at most 55% of the total ALMA sample. In addition to using literature spectroscopic and optical/NIR photometric redshifts, we estimate FIR photometric redshifts based on an Arp 220 template. We identify seven z>4 candidates. We see the expected decline with redshift of the 4.5 micron and 24 micron to 850 micron flux ratios, confirming these as good diagnostics of z>4 candidates. We visually classify 52 ALMA sources, finding 44% (68% confidence range 35-53%) to be apparent mergers. We calculate rest-frame 2-8 keV and 8-28 keV luminosities using the 7 Ms Chandra X-ray image. Nearly all of the ALMA sources detected at 0.5-2 keV are consistent with a known X-ray luminosity to 850 micron flux relation for star-forming galaxies, while most of those detected at 2-7 keV are moderate luminosity AGNs that lie just above the 2-7 keV detection threshold. The latter largely have substantial obscurations of log N_H = 23-24 cm^-2, but two of the high-redshift candidates may even be Compton thick.
Improving the capabilities of detecting faint X-ray sources is fundamental to increase the statistics on faint high-z AGN and star-forming galaxies. We performed a simultaneous Maximum Likelihood PSF fit in the [0.5-2] keV and [2-7] keV energy bands
of the 4 Ms{em Chandra} Deep Field South (CDFS) data at the position of the 34930 CANDELS H-band selected galaxies. For each detected source we provide X-ray photometry and optical counterpart validation. We validated this technique by means of a raytracing simulation. We detected a total of 698 X-ray point-sources with a likelihood $mathcal{L}$$>$4.98 (i.e. $>$2.7$sigma$). We show that the prior knowledge of a deep sample of Optical-NIR galaxies leads to a significant increase of the detection of faint (i.e. $sim$10$^{-17}$ cgs in the [0.5-2] keV band) sources with respect to blind X-ray detections. By including previous X-ray catalogs, this work increases the total number of X-ray sources detected in the 4 Ms CDFS, CANDELS area to 793, which represents the largest sample of extremely faint X-ray sources assembled to date. Our results suggest that a large fraction of the optical counterparts of our X-ray sources determined by likelihood ratio actually coincides with the priors used for the source detection. Most of the new detected sources are likely star-forming galaxies or faint absorbed AGN. We identified a few sources sources with putative photometric redshift z$>$4. Despite the low number statistics and the uncertainties on the photo-z, this sample significantly increases the number of X--ray selected candidate high-z AGN.
We use ~88 arcmin**2 of deep (>~26.5 mag at 5 sigma) NICMOS data over the two GOODS fields and the HDF South to conduct a search for bright z>~7 galaxy candidates. This search takes advantage of an efficient preselection over 58 arcmin**2 of NICMOS H
-band data where only plausible z>~7 candidates are followed up with NICMOS J-band observations. ~248 arcmin**2 of deep ground-based near-infrared data (>~25.5 mag, 5 sigma) is also considered in the search. In total, we report 15 z-dropout candidates over this area -- 7 of which are new to these search fields. Two possible z~9 J-dropout candidates are also found, but seem unlikely to correspond to z~9 galaxies. The present z~9 search is used to set upper limits on the prevalence of such sources. Rigorous testing is undertaken to establish the level of contamination of our selections by photometric scatter, low mass stars, supernovae (SNe), and spurious sources. The estimated contamination rate of our z~7 selection is ~24%. Through careful simulations, the effective volume available to our z>~7 selections is estimated and used to establish constraints on the volume density of luminous (L*(z=3), or -21 mag) galaxies from these searches. We find that the volume density of luminous star-forming galaxies at z~7 is 13_{-5}^{+8}x lower than at z~4 and >25x lower (1 sigma) at z~9 than at z~4. This is the most stringent constraint yet available on the volume density of >~L* galaxies at z~9. The present wide-area, multi-field search limits cosmic variance to <20%. The evolution we find at the bright end of the UV LF is similar to that found from recent Subaru Suprime-Cam, HAWK-I or ERS WFC3/IR searches. The present paper also includes a complete summary of our final z~7 z-dropout sample (18 candidates) identified from all NICMOS observations to date (over the two GOODS fields, the HUDF, galaxy clusters).
Lyman-Break Galaxy (LBG) samples observed during reionization ($zgtrsim6$) with Hubble Space Telescopes Wide Field Camera 3 are reaching sizes sufficient to characterize their clustering properties. Using a combined catalog from the Hubble eXtreme De
ep Field and CANDELS surveys, containing $N=743$ LBG candidates at z>6.5 at a mean redshift of $z=7.2$, we detect a clear clustering signal in the angular correlation function (ACF) at $sim4sigma$, corresponding to a real-space correlation length $r_{0}=6.7^{+0.9}_{-1.0}h^{-1}$cMpc. The derived galaxy bias $b=8.6^{+0.9}_{-1.0}$ is that of dark-matter halos of $M=10^{11.1^{+0.2}_{-0.3}}$M$_{odot}$ at $z=7.2$, and highlights that galaxies below the current detection limit ($M_{AB}sim-17.7$) are expected in lower-mass halos ($Msim10^{8}-10^{10.5}$M$_{odot}$). We compute the ACF of LBGs at $zsim3.8-zsim5.9$ in the same surveys. A trend of increasing bias is found from $z=3.8$ ($bsim3.0$) to $z=7.2$ ($bsim8.6$), broadly consistent with galaxies at fixed luminosity being hosted in dark-matter halos of similar mass at $4<z<6$, followed by a slight rise in halo masses at $zsim7$ ($sim2sigma$ confidence). Separating the data at the median luminosity of the $z=7.2$ sample ($M_{UV}=-19.4$) shows higher clustering at $z=5.9$ for bright galaxies ($r_{0}=5.5^{+1.4}_{-1.5}h^{-1}$cMpc, $b=6.2^{+1.2}_{-1.5}$) compared to faint galaxies ($r_{0}=1.9^{+1.1}_{-1.0}h^{-1}$cMpc, $b=2.7pm1.2$) implying a constant mass-to-light ratio $frac{dlogM}{dlogL}sim1.2^{+1.8}_{-0.8}$. A similar trend is present in the $z=7.2$ sample with larger uncertainty. Finally, our bias measurements allow us to investigate the fraction of dark-matter halos hosting UV-bright galaxies (the duty-cycle, $epsilon_{DC}$). At $z=7.2$ values near unity are preferred, which may be explained by the shortened halo assembly time at high-redshift.
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