Abstract
This paper presents the third data release of the Hyper Suprime-Cam Subaru Strategic Program (HSC-SSP), a wide-field multi-band imaging survey with the Subaru 8.2 m telescope. HSC-SSP has ...three survey layers (Wide, Deep, and UltraDeep) with different area coverages and depths, designed to address a wide array of astrophysical questions. This third release from HSC-SSP includes data from 278 nights of observing time and covers about 670 deg2 in all five broad-band filters (grizy) at the full depth (∼26 mag at 5σ depending on filter) in the Wide layer. If we include partially observed areas, the release covers 1470 deg2. The Deep and UltraDeep layers have $\sim\! 80\%$ of the originally planned integration times, and are considered done, as we have slightly changed the observing strategy in order to compensate for various time losses. There are a number of updates in the image processing pipeline. Of particular importance is the change in the sky subtraction algorithm; we subtract the sky on small scales before the detection and measurement stages, which has significantly reduced the number of false detections. Thanks to this and other updates, the overall quality of the processed data has improved since the previous release. However, there are limitations in the data (for example, the pipeline is not optimized for crowded fields), and we encourage the user to check the quality assurance plots as well as a list of known issues before exploiting the data. The data release website is 〈https://hsc-release.mtk.nao.ac.jp〉.
Abstract
This paper presents the second data release of the Hyper Suprime-Cam Subaru Strategic Program, a wide-field optical imaging survey using the 8.2 m Subaru Telescope. The release includes data ...from 174 nights of observation through 2018 January. The Wide layer data cover about 300 deg$^2$ in all five broad-band filters ($grizy$) to the nominal survey exposure (10 min in $gr$ and 20 min in $izy$). Partially observed areas are also included in the release; about 1100 deg$^2$ is observed in at least one filter and one exposure. The median seeing in the i-band is ${0_{.}^{\prime \prime }6}$, demonstrating the superb image quality of the survey. The Deep (26 deg$^2$) and UltraDeep (4 deg$^2$) data are jointly processed and the UltraDeep-COSMOS field reaches an unprecedented depth of $i\sim 28$ at $5 \, \sigma$ for point sources. In addition to the broad-band data, narrow-band data are also available in the Deep and UltraDeep fields. This release includes a major update to the processing pipeline, including improved sky subtraction, PSF modeling, object detection, and artifact rejection. The overall data quality has been improved, but this release is not without problems; there is a persistent deblender problem as well as new issues with masks around bright stars. The user is encouraged to review the issue list before utilizing the data for scientific explorations. All the image products as well as catalog products are available for download. The catalogs are also loaded into a database, which provides an easy interface for users to retrieve data for objects of interest. In addition to these main data products, detailed galaxy shape measurements withheld from Public Data Release 1 (PDR1) are now available to the community. The shape catalog is drawn from the S16A internal release, which has a larger area than PDR1 (160 deg$^2$). All products are available at the data release site, https://hsc-release.mtk.nao.ac.jp/.
ABSTRACT
We study the extent to which very bright (
) Lyman-break-selected galaxies at redshifts
display detectable Ly
α
emission. To explore this issue, we obtained follow-up optical spectroscopy of ...9
galaxies from a parent sample of 24
galaxy candidates selected from the 1.65 deg
2
COSMOS-UltraVISTA and SXDS-UDS survey fields using the latest near-infrared public survey data, and new ultra-deep Subaru
z
′-band imaging (which we also present and describe in this paper). Our spectroscopy yielded only one possible detection of Ly
α
at
z
= 7.168 with a rest-frame equivalent width
. The relative weakness of this line, combined with our failure to detect Ly
α
emission from the other spectroscopic targets, allows us to place a new upper limit on the prevalence of strong Ly
α
emission at these redshifts. For conservative calculation and to facilitate comparison with previous studies at lower redshifts, we derive a 1
σ
upper limit on the fraction of UV-bright galaxies at
that display
, which we estimate to be
. This result may indicate a weak trend where the fraction of strong Ly
α
emitters ceases to rise, and possibly falls between
z
≃ 6 and
. Our results also leave open the possibility that strong Ly
α
may still be more prevalent in the brightest galaxies in the reionization era than their fainter counterparts. A larger spectroscopic sample of galaxies is required to derive a more reliable constraint on the neutral hydrogen fraction at
based on the Ly
α
fraction in the bright galaxies.
We investigate mass-dependent galaxy evolution based on a large sample of (more than 50,000) K-band selected galaxies in a multi-wavelength catalog of the Subaru/XMM-Newton Deep Survey and the UKIRT ...Infrared Deep Sky Survey/Ultra Deep Survey. We employ optical to near-infrared photometry to determine photometric redshifts of these galaxies. Then, we estimate the stellar mass of our sample galaxies using a standard fitting procedure as we used for estimation of the photometric redshift. From the sample galaxies, we obtain the stellar mass function of galaxies and the cosmic stellar mass density up to z ~ 4. Our results are consistent with previous studies and we find a considerable number of low-mass galaxies (M * ~ 1010.5) at the redshift range 3 < z < 4. By combining stellar masses and spatial distributions of galaxies derived from a large number of galaxies in the contiguous wide and deep field, we examine properties of the mass-dependent clustering of galaxies. The correlation functions of our sample galaxies show clear evolution and they connect to that in the local universe consistently. Also, we find that the massive galaxies show strong clustering throughout our studied redshift range. The correlation length of massive galaxies rapidly decreases from z = 4 to 2. The mass of dark halos hosting the intermediate-mass value galaxies changes from high (1014 M ) to low (1013 M ) with decreasing redshift at around z ~ 2. We also find some high-mass density regions of massive galaxies at 1.4 <= z < 2.5 in our sample. These concentrations of massive galaxies may be candidate progenitors of the present-day clusters of galaxies. At this redshift range, massive star-forming galaxies are the dominant population making up the structures and the passively evolving galaxies show stronger clustering and they may have formed earlier than those star-forming galaxies.
ABSTRACT We study the extent to which very bright ( ) Lyman-break-selected galaxies at redshifts display detectable Ly emission. To explore this issue, we obtained follow-up optical spectroscopy of 9 ...galaxies from a parent sample of 24 galaxy candidates selected from the 1.65 deg2 COSMOS-UltraVISTA and SXDS-UDS survey fields using the latest near-infrared public survey data, and new ultra-deep Subaru z′-band imaging (which we also present and describe in this paper). Our spectroscopy yielded only one possible detection of Ly at z = 7.168 with a rest-frame equivalent width . The relative weakness of this line, combined with our failure to detect Ly emission from the other spectroscopic targets, allows us to place a new upper limit on the prevalence of strong Ly emission at these redshifts. For conservative calculation and to facilitate comparison with previous studies at lower redshifts, we derive a 1 upper limit on the fraction of UV-bright galaxies at that display , which we estimate to be . This result may indicate a weak trend where the fraction of strong Ly emitters ceases to rise, and possibly falls between z 6 and . Our results also leave open the possibility that strong Ly may still be more prevalent in the brightest galaxies in the reionization era than their fainter counterparts. A larger spectroscopic sample of galaxies is required to derive a more reliable constraint on the neutral hydrogen fraction at based on the Ly fraction in the bright galaxies.
This paper presents the second data release of the Hyper Suprime-Cam Subaru Strategic Program, a wide-field optical imaging survey using the 8.2 m Subaru Telescope. We report the release includes ...data from 174 nights of observation through 2018 January. The Wide layer data cover about 300 deg$^2$ in all five broad-band filters ($grizy$) to the nominal survey exposure (10 min in $gr$ and 20 min in $izy$). Partially observed areas are also included in the release; about 1100 deg$^2$ is observed in at least one filter and one exposure. The median seeing in the i-band is ${0_{.}^{\prime \prime }6}$, demonstrating the superb image quality of the survey. The Deep (26 deg$^2$) and UltraDeep (4 deg$^2$) data are jointly processed and the UltraDeep-COSMOS field reaches an unprecedented depth of $i\sim 28$ at $5 \, \sigma$ for point sources. In addition to the broad-band data, narrow-band data are also available in the Deep and UltraDeep fields. This release includes a major update to the processing pipeline, including improved sky subtraction, PSF modeling, object detection, and artifact rejection. The overall data quality has been improved, but this release is not without problems; there is a persistent deblender problem as well as new issues with masks around bright stars. The user is encouraged to review the issue list before utilizing the data for scientific explorations. All the image products as well as catalog products are available for download. The catalogs are also loaded into a database, which provides an easy interface for users to retrieve data for objects of interest. In addition to these main data products, detailed galaxy shape measurements withheld from Public Data Release 1 (PDR1) are now available to the community. The shape catalog is drawn from the S16A internal release, which has a larger area than PDR1 (160 deg$^2$). All products are available at the data release site, https://hsc-release.mtk.nao.ac.jp/.
Development and Operation of SMOKA NAKAJIMA, Yasushi; HIGUCHI, Aya; KAKUWA, Jun ...
Report of the National Astronomical Observatory of Japan,
2022/03/01, Letnik:
22
Journal Article
Odprti dostop
Twenty years have passed since we started the operation of SMOKA (Subaru-Mitaka-Okayama-Kiso Archive System). In this paper, we present an overview of SMOKA operations including its history, ...progress, various problems encountered and their solution, and statistics and achievements over the past twenty years. Furthermore, we present a discussion of issues to be considered for the next-generation system. We discuss the trends of data archive systems and instruments of astronomy in the world and make a proposal on the future astronomical data archive system.
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