884 research outputs found
Subaru FOCAS survey of z=7-7.1 Ly{\alpha} emitters: a test for z >~ 7 Ly{\alpha} photometric luminosity functions
Recent observations of z >~ 7 Ly{\alpha} emitters (LAEs) have derived a
variety of Ly{\alpha} luminosity functions (LFs) with contradictory results,
evolution or non-evolution from z <~ 6, the epoch after reionization. This
could be because most of z >~ 7 LFs comprise photometric candidates and might
include some contaminations. We conducted the Subaru Telescope Faint Object
Camera And Spectrograph narrowband NB980 ({\lambda}c ~ 9800A, FWHM ~ 100A)
imaging and spectroscopy survey of z=7-7.1 LAEs to compare its
"contamination-free" result with z >~ 7 photometric Ly{\alpha} LFs previously
derived. We imaged the Subaru Deep Field and the sky around a cluster MS
1520.1+3002 and found one LAE candidate, but spectroscopy did not reveal
Ly{\alpha} though deep enough to detect it. We calculated the expected number
of LAEs in our survey, using five z=7 and three z=7.7 Ly{\alpha} LFs from
recent surveys. Seven of them are consistent with null detection
(0.1^{+1.8}_{-0.1}-1.1^{+2.2}_{-1.0} LAEs) within errors including Poisson
statistics and cosmic variance, but average values (0.7-1.1 LAEs) predicted
from one z=7 and two z=7.7 LFs among the seven indicate nearly a single
detection. The remaining one z=7 LF predicts 3.0^{+3.2}_{-2.0} LAEs. As to z=7,
the discrepancy likely comes from different LAE selection criteria. For z=7.7,
there are two possibilities; (1) If z=7.7 LAEs are somehow brighter in
Ly{\alpha} luminosity than lower redshift LAEs, z=7.7 LF is observed to be
similar to or higher than lower redshift LFs even if attenuated by neutral
hydrogen. (2) All/most of the z=7.7 candidates are not LAEs. This supports the
decline of LF from z ~ 6 to 7.7 and reionization at z ~ 6-7.7.Comment: Accepted for publication in Monthly Notices of the Royal Astronomical
Society, 2012 March 0
Luminosity dependent clustering of star-forming BzK galaxies at redshift 2
We use the BzK color selection proposed by Daddi et al. (2004) to obtain a
sample of 1092 faint star-forming galaxies (hereafter sBzKs) from 180 arcmin^2
in the Subaru Deep Field. This sample represents star-forming galaxies at 1.4 <
z < 2.5 down to K(AB)=23.2, which roughly corresponds to a stellar-mass limit
of ~ 1 x 10^{10} Msun. We measure the angular correlation function (ACF) of
these sBzKs to be w(theta) = (0.58 +- 0.13) x theta["]^{-0.8} and translate the
amplitude into the correlation length assuming a reasonable redshift
distribution. The resulting value, r0 = 3.2^{+0.6}_{-0.7} h^{-1} Mpc, suggests
that our sBzKs reside in haloes with a typical mass of 2.8 x 10^{11} Msun.
Combining this halo mass estimate with those for brighter samples of Kong et
al. (2006), we find that the mass of dark haloes largely increases with K
brightness, a measure of the stellar mass. Comparison with other galaxy
populations suggests that faint sBzKs (K(AB)<23.2) and Lyman Break Galaxies at
z ~ 2 are similar populations hosted by relatively low-mass haloes, while
bright sBzKs (K(AB)<21) reside in haloes comparable to or more massive than
those of Distant Red Galaxies and Extremely Red Objects. Using the extended
Press-Schechter formalism, we predict that present-day descendants of haloes
hosting sBzKs span a wide mass range depending on K brightness, from lower than
that of the Milky Way up to those of richest clusters.Comment: 14 pages, 9 figures, accepted for publication in Ap
SpecPro: An Interactive IDL Program for Viewing and Analyzing Astronomical Spectra
We present an interactive IDL program for viewing and analyzing astronomical
spectra in the context of modern imaging surveys. SpecPro's interactive design
lets the user simultaneously view spectroscopic, photometric, and imaging data,
allowing for rapid object classification and redshift determination. The
spectroscopic redshift can be determined with automated cross-correlation
against a variety of spectral templates or by overlaying common emission and
absorption features on the 1-D and 2-D spectra. Stamp images as well as the
spectral energy distribution (SED) of a source can be displayed with the
interface, with the positions of prominent photometric features indicated on
the SED plot. Results can be saved to file from within the interface. In this
paper we discuss key program features and provide an overview of the required
data formats.Comment: Accepted for publication in the Publications of the Astronomical
Society of the Pacific (PASP) journal. Website: specpro.caltech.ed
A Subaru Weak Lensing Survey I: Cluster Candidates and Spectroscopic Verification
We present the results of an ongoing weak lensing survey conducted with the
Subaru telescope whose initial goal is to locate and study the distribution of
shear-selected structures or halos. Using a Suprime-cam imaging survey spanning
21.82 square degree, we present a catalog of 100 candidate halos located from
lensing convergence maps. Our sample is reliably drawn from that subset of our
survey area, (totaling 16.72 square degree) uncontaminated by bright stars and
edge effects and limited at a convergence signal to noise ratio of 3.69. To
validate the sample detailed spectroscopic measures have been made for 26
candidates using the Subaru multi-object spectrograph, FOCAS. All are confirmed
as clusters of galaxies but two arise as the superposition of multiple clusters
viewed along the line of sight. Including data available in the literature and
an ongoing Keck spectroscopic campaign, a total of 41 halos now have reliable
redshifts. For one of our survey fields, the XMM LSS (Pierre et al. 2004)
field, we compare our lensing-selected halo catalog with its X-ray equivalent.
Of 15 halos detected in the XMM-LSS field, 10 match with published X-ray
selected clusters and a further 2 are newly-detected and spectroscopically
confirmed in this work. Although three halos have not yet been confirmed, the
high success rate within the XMM-LSS field (12/15) confirms that weak lensing
provides a reliable method for constructing cluster catalogs, irrespective of
the nature of the constituent galaxies or the intracluster medium.Comment: To appear in ApJ, High resolution preprint available at
http://anela.mtk.nao.ac.jp/suprime33/papers/p1.ps.g
The UV-continuum properties of Ly alpha selected galaxies at z=6.5
We report the first space-based very deep near-infrared continuum
observations of a uniform sample of z = 6.5 galaxies with log(L(L_alpha)) =
42.5 - 43 erg/s selected from narrow-band line searches and with
spectroscopically confirmed Ly alpha emission. The 1.4 micron HST WFC3
observations are deep enough (AB(1 sigma) = 28.75) to measure individual
continuum magnitudes at this redshift for all of the objects. We compare the
results with continuum-selected samples at the same redshift and find that Ly
alpha emission is present in 24% of all galaxies with M_AB(1350 A) < -20 at z =
6.5. The error in this quantity is dominated by systematic uncertainties, which
could be as large as multiplicative factors of three. The Ly alpha galaxies are
extended but small (size < 1 kpc), and have star formation rates of
approximately 10 Msun/yr. We find a mean L(Ly alpha)/(nu L_nu) at 1400A of
0.08, with the seven objects showing a range from 0.026 to 0.26, implying that
there is little sign of destruction of the Ly alpha line. All of the properties
of the z = 6.5 sample appear to be very similar to those of Ly alpha emitters
at lower redshifts.Comment: Accepted for publication in the Astrophysical Journal Letter
"Direct" Gas-phase Metallicities, Stellar Properties, and Local Environments of Emission-line Galaxies at Redshift below 0.90
Using deep narrow-band (NB) imaging and optical spectroscopy from the Keck
telescope and MMT, we identify a sample of 20 emission-line galaxies (ELGs) at
z=0.065-0.90 where the weak auroral emission line, [OIII]4363, is detected at
>3\sigma. These detections allow us to determine the gas-phase metallicity
using the "direct'' method. With electron temperature measurements and dust
attenuation corrections from Balmer decrements, we find that 4 of these
low-mass galaxies are extremely metal-poor with 12+log(O/H) <= 7.65 or
one-tenth solar. Our most metal-deficient galaxy has 12+log(O/H) =
7.24^{+0.45}_{-0.30} (95% confidence), similar to some of the lowest
metallicity galaxies identified in the local universe. We find that our
galaxies are all undergoing significant star formation with average specific
star formation rate (SFR) of (100 Myr)^{-1}, and that they have high central
SFR surface densities (average of 0.5 Msun/yr/kpc^2. In addition, more than
two-thirds of our galaxies have between one and four nearby companions within a
projected radius of 100 kpc, which we find is an excess among star-forming
galaxies at z=0.4-0.85. We also find that the gas-phase metallicities for a
given stellar mass and SFR lie systematically below the local M-Z-(SFR)
relation by \approx0.2 dex (2\sigma\ significance). These results are partly
due to selection effects, since galaxies with strong star formation and low
metallicity are more likely to yield [OIII]4363 detections. Finally, the
observed higher ionization parameter and electron density suggest that they are
lower redshift analogs to typical z>1 galaxies.Comment: Accepted for publication in the Astrophysical Journal (15 November
2013). 31 pages in emulateapj format with 16 figures and 7 tables. Revised to
address referee's comments, which include discussion on selection effects,
similarities to green pea galaxies, and nebular continuum contribution.
Modifications were made for some electron temperature and metallicity
measurement
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