The Hyper Suprime-Cam software pipeline Bosch, James; Armstrong, Robert; Bickerton, Steven ...
Publications of the Astronomical Society of Japan,
01/2018, Letnik:
70, Številka:
SP1
Journal Article
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Abstract
In this paper, we describe the optical imaging data processing pipeline developed for the Subaru Telescope’s Hyper Suprime-Cam (HSC) instrument. The HSC Pipeline builds on the prototype ...pipeline being developed by the Large Synoptic Survey Telescope’s Data Management system, adding customizations for HSC, large-scale processing capabilities, and novel algorithms that have since been reincorporated into the LSST codebase. While designed primarily to reduce HSC Subaru Strategic Program (SSP) data, it is also the recommended pipeline for reducing general-observer HSC data. The HSC pipeline includes high-level processing steps that generate coadded images and science-ready catalogs as well as low-level detrending and image characterizations.
We report the discovery of 15 quasars and bright galaxies at 5.7 < z< 6.9. This is the initial result from the Subaru High-z Exploration of Low-Luminosity Quasars project, which exploits the ...exquisite multiband imaging data produced by the Subaru Hyper Suprime-Cam (HSC) Strategic Program survey. The candidate selection is performed by combining several photometric approaches including a Bayesian probabilistic algorithm to reject stars and dwarfs. The spectroscopic identification was carried out with the Gran Telescopio Canarias and the Subaru Telescope for the first 80 deg super(2) of the survey footprint. The success rate of our photometric selection is quite high, approaching 100% at the brighter magnitudes (z sub(AB)< 23.5 mag). Our selection also recovered all the known high-z quasars on the HSC images. Among the 15 discovered objects, six are likely quasars, while the other six with interstellar absorption lines and in some cases narrow emission lines are likely bright Lyman-break galaxies. The remaining three objects have weak continua and very strong and narrow Lyalpha lines, which may be excited by ultraviolet light from both young stars and quasars. These results indicate that we are starting to see the steep rise of the luminosity function of z> or = 6 galaxies, compared with that of quasars, at magnitudes fainter than M sub(1450)~ -22 mag or z sub(AB)~ 24 mag. Follow-up studies of the discovered objects as well as further survey observations are ongoing.
Abstract
We have developed an automated quick data analysis system for data quality assurance (QA) for Hyper Suprime-Cam (HSC). The system was commissioned in 2012–2014, and has been offered for ...general observations, including the HSC Subaru Strategic Program, since 2014 March. The system provides observers with data quality information, such as seeing, sky background level, and sky transparency, based on quick analysis as data are acquired. Quick-look images and validation of image focus are also provided through an interactive web application. The system is responsible for the automatic extraction of QA information from acquired raw data into a database, to assist with observation planning, assess progress of all observing programs, and monitor long-term efficiency variations of the instrument and telescope. Enhancements of the system are being planned to facilitate final data analysis, to improve the HSC archive, and to provide legacy products for astronomical communities.
Core-collapse supernovae (CC-SNe) are the explosions that announce the death of massive stars. Some CC-SNe are linked to long-duration gamma-ray bursts (GRBs) and are highly aspherical. One important ...question is to what extent asphericity is common to all CC-SNe. Here we present late-time spectra for a number of CC-SNe from stripped-envelope stars and use them to explore any asphericity generated in the inner part of the exploding star, near the site of collapse. A range of oxygen emission-line profiles is observed, including a high incidence of double-peaked profiles, a distinct signature of an aspherical explosion. Our results suggest that all CC-SNe from stripped-envelope stars are aspherical explosions and that SNe accompanied by GRBs exhibit the highest degree of asphericity.
We report on the multi-wavelength identification of the X-ray sources found in the Subaru–XMM-Newton Deep Survey (SXDS) using deep imaging data covering the wavelength range between the far-UV and ...mid-IR (MIR). We select a primary counterpart of each X-ray source by applying the likelihood ratio method to R-band, 3.6 μm, near-UV, and 24 μm source catalogs as well as matching catalogs of active galactic nucleus (AGN) candidates selected in 1.4 GHz radio and i
′-band variability surveys. Once candidates for Galactic stars, ultra-luminous X-ray sources in a nearby galaxy, and clusters of galaxies are removed there are 896 AGN candidates in the sample. We conduct spectroscopic observations of the primary counterparts with multi-object spectrographs in the optical and NIR; 65% of the X-ray AGN candidates are spectroscopically identified. For the remaining X-ray AGN candidates, we evaluate their photometric redshift with photometric data in 15 bands. Utilizing the multi-wavelength photometric data of the large sample of X-ray-selected AGNs, we evaluate the stellar masses, M
*, of the host galaxies of the narrow-line AGNs. The distribution of the stellar mass is remarkably constant from z = 0.1 to 4.0. The relation between M
* and 2–10 keV luminosity can be explained with strong cosmological evolution of the relationship between the black hole mass and M
*. We also evaluate the scatter of the UV–MIR spectral energy distribution (SED) of the X-ray AGNs as a function of X-ray luminosity and absorption by the nucleus. The scatter is compared with galaxies which have redshift and stellar mass distribution matched with the X-ray AGN. The UV–NIR (near-IR) SEDs of obscured X-ray AGNs are similar to those of the galaxies in the matched sample. In the NIR–MIR range, the median SEDs of X-ray AGNs are redder, but the scatter of the SEDs of the X-ray AGN broadly overlaps that of the galaxies in the matched sample.
The Faint Object Camera and Spectrograph (FOCAS) is a Cassegrain optical instrument for the Subaru Telescope. Its capabilities include
$6^\prime \phi$
FOV direct imaging, low-resolution spectroscopy ...(
$R=250 \hbox{--} 2000$
with
${0\rlap {.}{}^{\mathrm {\prime \prime }}4}$
slitwidth), multi-slit spectroscopy and polarimetry. We describe the overall design of FOCAS, its observing functions, and the performance verification procedures that have been carried out.
We develop an infinite mixture model of Ornstein-Uhlenbeck (OU) processes for describing the optical variability of QSOs based on treating the variability as a stochastic process. This enables us to ...get the parameters of the power spectral densities (PSDs) on their brightness variations by providing more flexible description of PSDs than the models based on a single OU process (damped random walk (DRW). We apply this model to 67,507 variable objects extracted from Sloan Digital Sky Survey (SDSS) Stripe 82 photometric data and succeed in showing very high precision in identifying QSOs (∼99% levels in completeness and purity) among variable objects based only on their variability, by investigating on 9855 spectroscopically confirmed objects (7714 QSOs and 2141 stars) in the data of SDSS Data Release 12 (DR12), with sufficient and accurate multiple measurements of their brightness. By comparing our results with the values based on other models that are used in previous research, it is revealed that our model can be used as the most effective method for selecting QSOs from a variable object catalog, especially regarding completeness and purity. The main reason for improved identification rates is the ability of our model to separate clearly QSOs and stars, especially on the small fraction of QSOs with variabilities that can be described better than with the simple DRW model.
ABSTRACT
We propose a geometric method of analysis for the light curves of active galactic nuclei (AGNs). The time series of flux ratio is modelled by possibly non-linear random oscillation without ...specifying the function form. Based on the model, we map the dynamic behaviour of flux ratio to a vector field on a manifold, and then analyse the vector field to retrieve information on the dynamic properties closely linked with the activity of AGNs. While the function form of the model is unspecified, the vector fields and those associated quantities can be estimated by applying a non-parametric filtering method. We illustrate the proposed analysis with an application to light curves of two AGNs supplied by the Kepler satellite. The application shows that the vector field, its derivative, and their combination will be used as the tools of picking up various signals that help understanding of the activity of AGNs. In addition, from a technical viewpoint, the non-parametric filtering method allows the estimation to be robust against outliers. The proposed analysis could be used as an alternative time series analysis of the optical variability other than the analysis by spectral densities or structure functions.
We present the result of a projected cross-correlation analysis of AGNs and galaxies at redshifts from 0.3 to 3.0. The Japanese Virtual Observatory (JVO) was used to obtain Subaru Suprime-Cam images ...and UKIDSS catalog data around AGNs. We investigated 1809 AGNs, which is about a ten-times larger sample than that used in previous studies on AGN–galaxy clustering at redshifts larger than 0.6; 90% of the AGN samples were optically-selected AGN from the SDSS and 2dF catalogs. The galaxy samples at low redshift include many redder objects from the UKIDSS survey, while at higher redshift they are mainly blue galaxies from Suprime-Cam. We found a significant excess of galaxies around the AGNs at redshifts from 0.3 to 1.8. For the low-redshift samples (z
$\lt$
0.9), we obtained a correlation length of
$r_{0}$
$=$
5–6
$\ h^{-1}$
Mpc (
$\gamma$
$=$
1.8), which indicates that the AGNs at this redshift range reside in a similar environment around typical local galaxies. We also found that AGNs at higher redshift ranges reside in a denser environment than lower redshift AGNs. For z
$=$
1.3–1.8 AGNs, the cross-correlation length was measured as 11
$^{+6}_{-3}\ h^{-1}$
Mpc (
$\gamma$
$=$
1.8). Considering that our sample of galaxies is based on optical observations with Suprime-Cam at the redshift range, it is expected that blue star-forming galaxies comprise the majority of objects that are observed to be clustered around the AGNs. It has been successfully demonstrated that using the archive through the Virtual Observatory system can provide a powerful tool for investigating the small-scale environment of intermediate redshift AGNs.
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