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Register a new userProper motions with Subaru I. Methods and a first sample in the Subaru Deep Field
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We search for stars with proper motions in a set of twenty deep Subaru images, covering about 0.28 square degrees to a depth of i ~ 25, taken over a span of six years. In this paper, we describe in detail our reduction and techniques to identify moving objects. We present a first sample of 99 stars with motions of high significance, and discuss briefly the populations from which they are likely drawn. Based on photometry and motions alone, we expect that 9 of the candidates may be white dwarfs. We also find a group of stars which may be extremely metal-poor subdwarfs in the halo.
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We present a deep $K^{prime}$-band (2.12$mu$m) imaging of 1arcmin $times$ 1arcmin Subaru Super Deep Field (SSDF) taken with the Subaru adaptive optics (AO) system. Total integration time of 26.8 hours results in the limiting magnitude of $K^{prime} sim 24.7$ (5$sigma$, 0farcs2 aperture) for point sources and $K^{prime} sim 23.5$ (5$sigma$, 0farcs6 aperture) for galaxies, which is the deepest limit ever achieved in the $K^{prime}$ band. The average stellar FWHM of the co-added image is 0farcs18. Based on the photometric measurements of detected galaxies, we obtained the differential galaxy number counts, for the first time, down to $K^{prime} sim 25$, which is more than 0.5 mag deeper than the previous data. We found that the number count slope $dlog N/dm$ is about 0.15 at $22 < K^{prime} < 25$, which is flatter than the previous data. Therefore, detected galaxies in the SSDF have only negligible contribution to the near-infrared extragalactic background light (EBL), and the discrepancy claimed so far between the diffuse EBL measurements and the estimated EBL from galaxy count integration has become more serious . The size distribution of detected galaxies was obtained down to the area size of less than 0.1 arcsec$^2$, which is less than a half of the previous data in the $K^{prime}$ band. We compared the observed size-magnitude relation with a simple pure luminosity evolution model allowing for intrinsic size evolution, and found that a model with no size evolution gives the best fit to the data. It implies that the surface brightness of galaxies at high redshift is not much different from that expected from the size-luminosity relation of present-day galaxies.
In order to search for high-redshift galaxies beyond $z = 6.6$ in the Subaru Deep Field, we have investigated NB921-dropout galaxies where NB921 is the narrowband filter centered at 919.6 nm with FWHM of 13.2 nm for the Suprime-Cam on the Subaru Telescope. There are no secure NB921-dropout candidates brighter than $z^prime = 25.5$. Based on this result, we discuss the UV luminosity function of star-forming galaxies at $z > 6.6$.
Deep near-infrared images of a blank 2x2 section of sky near the Galactic north pole taken by Subaru Telescope are presented. The total integration times of the J and K bands are 12.1 hours and 9.7 hours, resulting in 5-sigma limiting magnitudes of 25.1 and 23.5 mag, respectively. The numbers of sources within these limiting magnitudes found with an automated detection procedure are 385 in the J band and 350 in K. Based on photometric measurements of these sources, we present number count vs. magnitude relations, color vs. magnitude diagrams, size vs. color relationships, etc. The slope of the galaxy number count plotted against the AB magnitude scale is about 0.23 in the 22 to 26 AB magnitude range of both bands. The spatial number density of galaxies as well as the slopes in the faint-end region given by the Subaru Deep Field (SDF) survey is consistent with those given by HST-NICMOS surveys as expressed on the AB magnitude diagram. Several sources having very large J-K color are found including a few K objects without detection at J. In addition, a number of faint Galactic stars are also detected, most of which are assigned to M-subdwarfs, together with a few brown dwarf candidates.
The Subaru Deep Field (SDF) project is a program of Subaru Observatory to carry out a deep galaxy survey over a blank field as large as 34x27. The program consists of very deep multi-band optical imaging, near infrared imaging for smaller portions of the field and follow-up optical spectroscopy. Major scientific goals of the project are to construct large samples of Lyman-break galaxies at z~4-5 and Lyman alpha emitters at z~5.7 and 6.6, and to make detailed studies these very high-redshift galaxy populations. In this paper, we describe the optical imaging observations and data reduction, presenting mosaicked images and object catalogs in seven bandpasses.The optical imaging was made through five broad-band filters, B, V, R, i, z, and two narrow-band filters, NB816 (lambda_c=8150A) and NB921 (lambda_c=9196A) with almost 10 hours long integrations for each band. The limiting magnitudes measured at 3-sigma on a 2 aperture are B=28.45, V=27.74, R=27.80, i=27.43, z=26.62, NB816=26.63, and NB921=26.54 in the AB system. The object catalog constructed for each of the seven bands contains more than 10^5 objects. The galaxy number counts corrected for detection incompleteness and star count contribution are found to be consistent with previous results in the literature. The mosaicked images and catalogs of all the bands have been made open to the public on Oct. 1, 2004 on the SDF project website at http://soaps.naoj.org/sdf/.
We present observations of SDF-05M05, an unusual optical transient discovered in the Subaru Deep Field (SDF). The duration of the transient is > ~800 d in the observer frame, and the maximum brightness during observation reached approximately 23 mag in the i and z bands. The faint host galaxy is clearly identified in all 5 optical bands of the deep SDF images. The photometric redshift of the host yields z~0.6 and the corresponding absolute magnitude at maximum is ~-20. This implies that this event shone with an absolute magnitude brighter than -19 mag for approximately 300 d in the rest frame, which is significantly longer than a typical supernova and ultra-luminous supernova. The total radiated energy during our observation was 1x10^51 erg. The light curves and color evolution are marginally consistent with some of luminous IIn supernova. We suggest that the transient may be a unique and peculiar supernova at intermediate redshift.
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