We performed a deep optical imaging survey using a narrow-band filter (NB921) centered at
$\lambda = 9196 \,$
Å together with
$i^\prime$
and
$z^\prime$
broadband filters covering an
$814 ...\,\mathrm{arcmin}^2$
area of the Subaru Deep Field. We obtained a sample of 73 strong NB921-excess objects based on the following two color criteria:
$z^\prime-\mathit{NB}\,921 \gt 1$
$z^\prime-\mathit{NB}\,921 \gt 1$
and
$i^\prime-z^\prime \gt 1.3$
$i^\prime-z^\prime \gt 1.3$
. We then obtained optical spectroscopy of nine objects in our NB921-excess sample, and identified at least two Ly
$\alpha$
emitters at
$z=6.541 \pm 0.002$
and
$z=6.578 \pm 0.002$
, each of which shows the characteristic sharp cutoff together with continuum depression at wavelengths shortward of the line peak. The latter object is more distant than HCM-6A at
$z=6.56$
, which is the most distant known object that has been found so far. These new data allow us to estimate the first meaningful lower limit of the star-formation rate density beyond redshift 6;
$\rho_\mathrm{SFR} \sim 5.2 \times 10^{-4} \,{{{M}_{\odot}}} \,\mathrm{yr}^{-1} \,\mathrm{Mpc}^{-3}$
. Since it is expected that the actual density is several times higher than this value, our new observation reveals that a moderately high level of star formation activity already occurred at
$z \sim 6.6$
.
An overview of the current status of the 8.2 m Subaru Telescope constructed and operated at Mauna Kea, Hawaii, by the National Astronomical Observatory of Japan is presented. The basic design concept ...and the verified performance of the telescope system are described. Also given are the status of the instrument package offered to the astronomical community, the status of operation, and some of the future plans. The status of the telescope reported in a number of SPIE papers as of the summer of 2002 are incorporated with some updates included as of 2004 February. However, readers are encouraged to check the most updated status of the telescope through the home page, http://subarutelescope.org/index.html, and/or the direct contact with the observatory staff.
We present the results of deep
$K^\prime$
- and
$J$
-band imaging of the field of a proto-cluster region near the radio galaxy 53W002 at
$z=2.390$
with the Subaru Telescope. The data were analyzed ...together with deep optical and near-infrared (NIR) images taken with the Hubble Space Telescope to investigate the properties of ten optically compact emission-line galaxies and candidates. Excluding the three objects which may contain active galactic nuclei, many are faint or undetected at
$K^\prime$
(
$\lambda_\mathrm{rest} \approx 6000 \,{Å}$
), and are therefore revealed to be intrinsically small starbursting objects. On the other hand, we detect few objects with colors and magnitudes expected for quiescent massive galaxies at
$z=2.4$
in the field.
Abstract
We studied the evolution of elliptical galaxies at $z \gtrsim 1$ using a sample of 247 Extremely Red Objects (EROs) with $R-K_\mathrm{s} \ge 3.35$ (AB) and $K_\mathrm{s} \le 22.1$ (AB) ...constructed from $BVR \, i'z'JHK_\mathrm{s}$ multicolor data of a $114 \,\mathrm{arcmin}^2$ area in the Subaru/XMM-Newton Deep Field taken with the Subaru Telescope and the UH 2.2 m telescope. By fitting template spectra of old galaxies (OGs) and young, dusty starbursts (DSs) to the multicolor data, we classified EROs into these two classes and estimated their redshifts. We found that 58% of the EROs in our sample belong to the OG class and that these OGs have a wide range of colors at any redshift. We derived rest-frame $B$-band luminosity functions of OGs in our sample at $z=1 \hbox{-} 1.5$ and $1.5 \hbox{-} 2.5$, and found that the number density of galaxies obeying passive evolution drops at $z \gtrsim 1.5$ by a factor of three or more. The spatial correlation length of OGs is estimated to be $r_0 \gtrsim 8 \,h^{-1} \,\mathrm{Mpc}$, which is comparable to, or larger than, those of present-day early-type galaxies of similar luminosities. We also discussed properties of DSs in our data.
Superwind-Driven Intense H2 Emission in NGC 6240 Ohyama, Youichi; Yoshida, Michitoshi; Takata, Tadafumi ...
Publications of the Astronomical Society of Japan,
08/2000, Letnik:
52, Številka:
4
Journal Article
Recenzirano
We have performed a long-slit K-band spectroscopic observation of the luminous infrared galaxy NGC 6240. Spatially extended H2 emission is detected over 3.3 kpc around the two nuclei. The peak ...position of the H2v = 1–0 S(1) emission is located at ∼ 0″.3–0″.4 north of the southern nucleus. Based on line-ratio analyses, we suggest that the excitation mechanism of H2 is pure thermal at most positions. We find the following three velocity components in the H2 emission around the southern nucleus and its south region: a blue-shifted component (≈ –250 km s−1 with respect to Vsys), which is recognized as a distinct C-shape distortion in the velocity field around the southern nucleus; a high-velocity blue-shifted “wing” component (∼ –1000 km s-1 with respect to Vsys); and a component indicating possible line splitting of ∼ 500 km s−1. We show that these kinematic properties can be reproduced by expanding motion of a shell-like structure around the southern nucleus. The offset peak position of the H2 emission can be understood if we assume that the shell expanding to the north interacts with the extragalactic molecular gas which has been transferred during the merging of the two nuclei. At the interface the cloud-crushing mechanism may work efficiently, and shock-excited intense H2 emission is thus expected there. With this mechanism, the H2 luminosity can be explained without global shock driven by the collision of two nuclei. All of these findings lead us to propose a model in which most of the H2 emission is attributed to shock excitation driven by the superwind activity of the southern nucleus.
We present low-resolution (R ~ 90) and medium-resolution (R ~ 2500) spectropolarimetry of nova V475 Sct taken with the HBS instrument, mounted on the 0.91 m telescope at the Okayama Astrophysical ...Observatory, and taken with the Faint Object Camera and Spectrograph, mounted on the 8.2 m Subaru telescope. We estimated the interstellar polarization toward the nova from the steady continuum polarization components and Ha line emission components. After subtracting the interstellar polarization component from the observations, we found that the Ha emission seen on 2003 October 7 was clearly polarized. In the polarized flux spectrum the Ha emission had a distinct red wing extending to ~+4900 km s-1 and a shoulder around +3500 km s-1, showing a constant position angle (P.A.) of linear polarization c* 155° ± 15°. This suggests that the nova had an asymmetric outflow with a velocity of vwind 3500 km s-1 or more, which is 6 times higher than the expansion velocity of the ionized shell at the same epoch. Such a high-velocity component has not previously been reported for a nova in the 'moderately fast' speed class. Our observations suggest the occurrence of violent mass-loss activity in the nova binary system even during the common-envelope phase. The P.A. of the polarization in the Ha wing is in good agreement with that of the continuum polarization found on 2003 September 26 (p* 0.4%-0.6%), which disappeared within the following 2 days. The uniformity of the P.A. between the continuum polarization and the wing polarization on October 7 suggests that the axis of the circumstellar asymmetry remained nearly constant during the period of our observations.
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