-
B. Bassett,
A. Becker,
D. Bizyaev,
H. Brewington,
C. Choi,
D. Cinabro,
C. D'Andrea,
J. Dembicky,
D. L. Depoy,
B. Dilday, [......],
D. McGinnis,
A. Aragon-Salamanca,
M. Bremer,
M. Turatto,
P. Ruiz-Lapuente,
F. Castander,
A. K. Romer,
C. Collins,
J. Lucey,
A. Edge
Central Bureau Electronic Telegrams. 02/2013; 1102:1.
-
B. Bassett,
A. Becker,
D. Bizyaev,
H. Brewington,
C. Choi,
D. Cinabro,
C. D'Andrea,
J. Dembicky,
D. L. Depoy,
B. Dilday, [......],
W. Kollatschny,
R. Assef,
M. Peeples,
M. Molla,
F. Castander,
R. Miquel,
D. McGinnis,
P. Challis,
G. Narayan,
R. Kirshner
Central Bureau Electronic Telegrams. 02/2013; 1098:1.
-
J. Meyers,
G. Aldering,
K. Barbary,
L. F. Barrientos,
M. Brodwin,
K. S. Dawson,
S. Deustua, M. Doi,
P. Eisenhardt,
L. Faccioli, [......],
P. Rosati,
D. Rubin,
E. Rykoff,
A. Spadafora,
S. A. Stanford,
N. Suzuki,
N. Takanashi,
K. Tokita,
N. Yasuda,
for the Supernova Cosmology Project
[show abstract]
[hide abstract]
ABSTRACT: Using the sample of Type Ia supernovae (SNe Ia) discovered by the Hubble
Space Telescope (HST) Cluster Supernova Survey and augmented with HST-observed
SNe Ia in the GOODS fields, we search for correlations between the properties
of SNe and their host galaxies at high redshift. We use galaxy color and
quantitative morphology to determine the red sequence in 25 clusters and
develop a model to distinguish passively evolving early-type galaxies from
star-forming galaxies in both clusters and the field. With this approach, we
identify six SN Ia hosts that are early-type cluster members and eleven SN Ia
hosts that are early-type field galaxies. We confirm for the first time at
z>0.9 that SNe Ia hosted by early-type galaxies brighten and fade more quickly
than SNe Ia hosted by late-type galaxies. We also show that the two samples of
hosts produce SNe Ia with similar color distributions. The relatively simple
spectral energy distributions (SEDs) expected for passive galaxies enable us to
measure stellar masses of early-type SN hosts. In combination with stellar mass
estimates of late-type GOODS SN hosts from Thomson & Chary (2011), we
investigate the correlation of host mass with Hubble residual observed at lower
redshifts. Although the sample is small and the uncertainties are large, a hint
of this relation is found at z>0.9. By simultaneously fitting the average
cluster galaxy formation history and dust content to the red-sequence scatters,
we show that the reddening of early-type cluster SN hosts is likely E(B-V) <~
0.06. The similarity of the field and cluster early-type host samples suggests
that field early-type galaxies that lie on the red sequence may also be
minimally affected by dust. Hence, the early-type hosted SNe Ia studied here
occupy a more favorable environment to use as well-characterized high-redshift
standard candles than other SNe Ia.
01/2012;
-
K. Barbary,
G. Aldering,
R. Amanullah,
M. Brodwin,
N. Connolly,
K. S. Dawson, M Doi,
P. Eisenhardt,
L. Faccioli,
V. Fadeyev, [......],
D. Rubin,
D. J. Schlegel,
A. L. Spadafora,
S. A. Stanford,
M Strovink,
N Suzuki,
N. Takanashi,
K. Tokita,
N Yasuda,
for the Supernova Cosmology Project
[show abstract]
[hide abstract]
ABSTRACT: We present a measurement of the volumetric Type Ia supernova (SN Ia) rate out
to z ~ 1.6 from the Hubble Space Telescope Cluster Supernova Survey. In
observations spanning 189 orbits with the Advanced Camera for Surveys we
discovered 29 SNe, of which approximately 20 are SNe Ia. Twelve of these SNe Ia
are located in the foregrounds and backgrounds of the clusters targeted in the
survey. Using these new data, we derive the volumetric SN Ia rate in four broad
redshift bins, finding results consistent with previous measurements at z > 1
and strengthening the case for a SN Ia rate that is equal to or greater than
~0.6 x 10^-4/yr/Mpc^3 at z ~ 1 and flattening out at higher redshift. We
provide SN candidates and efficiency calculations in a form that makes it easy
to rebin and combine these results with other measurements for increased
statistics. Finally, we compare the assumptions about host-galaxy dust
extinction used in different high-redshift rate measurements, finding that
different assumptions may induce significant systematic differences between
measurements.
10/2011;
-
N. Suzuki,
D. Rubin,
C. Lidman,
G. Aldering,
R. Amanullah,
K. Barbary,
L. F. Barrientos,
J. Botyanszki,
M. Brodwin,
N. Connolly, [......],
S. A. Stanford,
V. Stanishev,
D. Stern,
M. Strovink,
N. Takanashi,
K. Tokita,
M. Wagner,
L. Wang,
N. Yasuda,
H. K. C. Yee
[show abstract]
[hide abstract]
ABSTRACT: We present ACS, NICMOS, and Keck AO-assisted photometry of 20 Type Ia
supernovae SNe Ia from the HST Cluster Supernova Survey. The SNe Ia were
discovered over the redshift interval 0.623 < z < 1.415. Fourteen of these SNe
Ia pass our strict selection cuts and are used in combination with the world's
sample of SNe Ia to derive the best current constraints on dark energy. Ten of
our new SNe Ia are beyond redshift $z=1$, thereby nearly doubling the
statistical weight of HST-discovered SNe Ia beyond this redshift. Our detailed
analysis corrects for the recently identified correlation between SN Ia
luminosity and host galaxy mass and corrects the NICMOS zeropoint at the count
rates appropriate for very distant SNe Ia. Adding these supernovae improves the
best combined constraint on the dark energy density \rho_{DE}(z) at redshifts
1.0 < z < 1.6 by 18% (including systematic errors). For a LambdaCDM universe,
we find \Omega_\Lambda = 0.724 +0.015/-0.016 (68% CL including systematic
errors). For a flat wCDM model, we measure a constant dark energy
equation-of-state parameter w = -0.985 +0.071/-0.077 (68% CL). Curvature is
constrained to ~0.7% in the owCDM model and to ~2% in a model in which dark
energy is allowed to vary with parameters w_0 and w_a. Tightening further the
constraints on the time evolution of dark energy will require several
improvements, including high-quality multi-passband photometry of a sample of
several dozen z>1 SNe Ia. We describe how such a sample could be efficiently
obtained by targeting cluster fields with WFC3 on HST.
The Astrophysical Journal 05/2011; 746(1). · 6.02 Impact Factor
-
N Suzuki,
D Rubin,
C Lidman,
G Aldering,
R Amanullah,
K Barbary,
L F Barrientos,
J Botyanszki,
M Brodwin,
N Connolly, [......],
S Perlmutter,
M Postman,
T Pritchard,
J Rhodes,
P Ripoche,
P Rosati,
D J Schlegel,
A Spadafora,
S A Stanford,
W M Keck
[show abstract]
[hide abstract]
ABSTRACT: We present ACS, NICMOS, and Keck AO-assisted photometry of 20 Type Ia supernovae (SNe Ia) from the HST Cluster Supernova Survey. The SNe Ia were discovered over the redshift interval 0.623 < z < 1.415. Fourteen of these SNe Ia pass our strict selection cuts and are used in combination with the world's sample of SNe Ia to derive the best current constraints on dark energy. Ten of our new SNe Ia are beyond redshift z = 1, thereby nearly doubling the statistical weight of HST-discovered SNe Ia beyond this redshift. Our detailed analysis corrects for the recently identified correlation between SN Ia luminosity and host galaxy mass and corrects the NICMOS zeropoint at the count rates appropriate for very distant SNe Ia. Adding these supernovae improves the best combined constraint on dark energy density, ρ DE (z), at redshifts 1.0 < z < 1.6 by 18% (including systematic errors). For a flat ΛCDM universe, we find Ω Λ = 0.729 +0.014 −0.014 (68% CL including systematic errors). For a flat wCDM model, we measure a constant dark energy equation-of-state parameter w = −1.013 +0.068 −0.073 (68% CL). Curvature is constrained to ∼ 0.7% in the owCDM model and to ∼ 2% in a model in which dark energy is allowed to vary with parameters w 0 and w a . Tightening further the constraints on the time evolution of dark energy will require several improvements, including high-quality multi-passband photometry of a sample of several dozen z > 1 SNe Ia. We describe how such a sample could be efficiently obtained by targeting cluster fields with WFC3 on HST.
N. PANAGIA. 04/2011; 27292528323839(43).
-
K. Barbary,
G. Aldering,
R. Amanullah,
M. Brodwin,
N. Connolly,
K. S. Dawson, M Doi,
P. Eisenhardt,
L. Faccioli,
V. Fadeyev, [......],
D. Rubin,
D. J. Schlegel,
A. L. Spadafora,
S. A. Stanford,
M Strovink,
N Suzuki,
N. Takanashi,
K. Tokita,
N Yasuda,
for the Supernova Cosmology Project
[show abstract]
[hide abstract]
ABSTRACT: We report a measurement of the Type Ia supernova (SN Ia) rate in galaxy
clusters at 0.9 < z < 1.45 from the Hubble Space Telescope (HST) Cluster
Supernova Survey. This is the first cluster SN Ia rate measurement with
detected z > 0.9 SNe. Finding 8 +/- 1 cluster SNe Ia, we determine a SN Ia rate
of 0.50 +0.23-0.19 (stat) +0.10-0.09 (sys) SNuB (SNuB = 10^-12 SNe L_{sun,B}^-1
yr^-1). In units of stellar mass, this translates to 0.36 +0.16-0.13 (stat)
+0.07-0.06 (sys) SNuM (SNuM = 10^-12 SNe M_sun^-1 yr^-1). This represents a
factor of approximately 5 +/- 2 increase over measurements of the cluster rate
at z < 0.2. We parameterize the late-time SN Ia delay time distribution with a
power law (proportional to t^s). Under the assumption of a cluster formation
redshift of z_f = 3, our rate measurement in combination with lower-redshift
cluster SN Ia rates constrains s = -1.41 +0.47/-0.40, consistent with
measurements of the delay time distribution in the field. This measurement is
generally consistent with expectations for the "double degenerate" scenario and
inconsistent with some models for the "single degenerate" scenario predicting a
steeper delay time distribution at large delay times. We check for
environmental dependence and the influence of younger stellar populations by
calculating the rate specifically in cluster red-sequence galaxies and in
morphologically early-type galaxies, finding results similar to the full
cluster rate. Finally, the upper limit of one host-less cluster SN Ia detected
in the survey implies that the fraction of stars in the intra-cluster medium is
less than 0.47 (95% confidence), consistent with measurements at lower
redshifts.
The Astrophysical Journal 10/2010; 745(1). · 6.02 Impact Factor
-
R. Amanullah,
C. Lidman,
D. Rubin,
G. Aldering,
P. Astier,
K. Barbary,
M. S. Burns,
A. Conley,
K. S. Dawson,
S. E. Deustua, [......],
N. Panagia,
S. Perlmutter,
J. Raux,
P. Ruiz-Lapuente,
A. L. Spadafora,
M. Strovink,
N. Suzuki,
L. Wang,
W. M. Wood-Vasey,
N. Yasuda
[show abstract]
[hide abstract]
ABSTRACT: We report on work to increase the number of well-measured Type Ia supernovae (SNe Ia) at high redshifts. Light curves, including high signal-to-noise Hubble Space Telescope data, and spectra of six SNe Ia that were discovered during 2001, are presented. Additionally, for the two SNe with z > 1, we present ground-based J-band photometry from Gemini and the Very Large Telescope. These are among the most distant SNe Ia for which ground-based near-IR observations have been obtained. We add these six SNe Ia together with other data sets that have recently become available in the literature to the Union compilation. We have made a number of refinements to the Union analysis chain, the most important ones being the refitting of all light curves with the SALT2 fitter and an improved handling of systematic errors. We call this new compilation, consisting of 557 SNe, the Union2 compilation. The flat concordance ΛCDM model remains an excellent fit to the Union2 data with the best-fit constant equation-of-state parameter w = –0.997+0.050 –0.054(stat)+0.077 –0.082(stat + sys together) for a flat universe, or w = –1.038+0.056 –0.059(stat)+0.093 –0.097(stat + sys together) with curvature. We also present improved constraints on w(z). While no significant change in w with redshift is detected, there is still considerable room for evolution in w. The strength of the constraints depends strongly on redshift. In particular, at z 1, the existence and nature of dark energy are only weakly constrained by the data.
The Astrophysical Journal 05/2010; 716(1):712. · 6.02 Impact Factor
-
R. Amanullah,
C. Lidman,
D. Rubin,
G. Aldering,
P. Astier,
K. Barbary,
M. S. Burns,
A. Conley,
K. S. Dawson,
S. E. Deustua, [......],
N. Panagia,
S. Perlmutter,
J. Raux,
P. Ruiz-Lapuente,
A. L. Spadafora,
M Strovink,
N Suzuki,
L Wang,
W. M. Wood-Vasey,
N Yasuda
[show abstract]
[hide abstract]
ABSTRACT: We report on work to increase the number of well-measured Type Ia supernovae
(SNe Ia) at high redshifts. Light curves, including high signal-to-noise HST
data, and spectra of six SNe Ia that were discovered during 2001 are presented.
Additionally, for the two SNe with z>1, we present ground-based J-band
photometry from Gemini and the VLT. These are among the most distant SNe Ia for
which ground based near-IR observations have been obtained. We add these six
SNe Ia together with other data sets that have recently become available in the
literature to the Union compilation (Kowalski et al. 2008). We have made a
number of refinements to the Union analysis chain, the most important ones
being the refitting of all light curves with the SALT2 fitter and an improved
handling of systematic errors. We call this new compilation, consisting of 557
supernovae, the Union2 compilation. The flat concordance LambdaCDM model
remains an excellent fit to the Union2 data with the best fit constant equation
of state parameter w=-0.997^{+0.050}_{-0.054} (stat) ^{+0.077}_{-0.082}
(stat+sys\ together) for a flat universe, or w=-1.035^{+0.055}_{-0.059}
(stat)^{+0.093}_{-0.097} (stat+sys together) with curvature. We also present
improved constraints on w(z). While no significant change in w with redshift is
detected, there is still considerable room for evolution in w. The strength of
the constraints depend strongly on redshift. In particular, at z > 1, the
existence and nature of dark energy are only weakly constrained by the data.
04/2010;
-
X. Huang,
T. Morokuma,
H. K. Fakhouri,
G. Aldering,
R. Amanullah,
K. Barbary,
M. Brodwin,
N. V. Connolly,
K. S. Dawson, M. Doi, [......],
C. Lidman,
J. Meyers,
L. A. Moustakas,
S. Perlmutter,
D. Rubin,
D. J. Schlegel,
A. L. Spadafora,
N. Suzuki,
N. Takanashi,
and N. Yasuda
[show abstract]
[hide abstract]
ABSTRACT: We report the discovery of a multiply lensed Lyα emitter at z = 3.90 behind the massive cluster WARPS J1415.1+3612 at z = 1.026. Images taken by the Hubble Space Telescope using the Advanced Camera for Surveys reveal a complex lensing system that produces a prominent, highly magnified arc and a triplet of smaller arcs grouped tightly around a spectroscopically confirmed cluster member. Spectroscopic observations using the Faint Object Camera and Spectrograph on Subaru confirm strong Lyα emission in the source galaxy and provide the redshifts for more than 21 cluster members with a velocity dispersion of 807 ± 185 km s–1. Assuming a singular isothermal sphere profile, the mass within the Einstein ring (7.13 ± 038) corresponds to a central velocity dispersion of 686+15 –19 km s–1 for the cluster, consistent with the value estimated from cluster member redshifts. Our mass profile estimate from combining strong lensing and dynamical analyses is in good agreement with both X-ray and weak lensing results.
The Astrophysical Journal 11/2009; 707(1):L12. · 6.02 Impact Factor
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X Huang,
T. Morokuma,
H. K. Fakhouri,
G. Aldering,
R. Amanullah,
K. Barbary,
M. Brodwin,
N. V. Connolly,
K. S. Dawson, M Doi, [......],
C. Lidman,
J. Meyers,
L. A. Moustakas,
S. Perlmutter,
D. Rubin,
D. J. Schlegel,
A. L. Spadafora,
N Suzuki,
N. Takanashi,
N Yasuda
[show abstract]
[hide abstract]
ABSTRACT: We report the discovery of a multiply lensed Ly Alpha (Lya) emitter at z = 3.90 behind the massive galaxy cluster WARPS J1415.1+3612 at z = 1.026. Images taken by the Hubble Space Telescope(HST) using ACS reveal a complex lensing system that produces a prominent, highly magnified arc and a triplet of smaller arcs grouped tightly around a spectroscopically confirmed cluster member. Spectroscopic observations using FOCAS on Subaru confirm strong Lya emission in the source galaxy and provide redshifts for more than 21 cluster members, from which we obtain a velocity dispersion of 807+/-185 km/s. Assuming a singular isothermal sphere profile, the mass within the Einstein ring (7.13+/-0.38") corresponds to a central velocity dispersion of 686+15-19 km/s for the cluster, consistent with the value estimated from cluster member redshifts. Our mass profile estimate from combining strong lensing and dynamical analyses is in good agreement with both X-ray and weak lensing results. Comment: 5 pages, 2 figures, accepted by ApJL. See http://www.supernova.lbl.gov/ for additional information pertaining to the HST Cluster SN Survey. (This added URL is the only change in this version.)
11/2009;
-
K. S. Dawson,
G. Aldering,
R. Amanullah,
K. Barbary,
L. F. Barrientos,
M. Brodwin,
N. Connolly,
A. Dey, M Doi,
M. Donahue, [......],
V. Stanishev,
D. Stern,
M Strovink,
N Suzuki,
N. Takanashi,
K. Tokita,
M Wagner,
L Wang,
N Yasuda,
H. K. C. Yee
[show abstract]
[hide abstract]
ABSTRACT: We present a new survey strategy to discover and study high redshift Type Ia supernovae (SNe Ia) using the Hubble Space Telescope (HST). By targeting massive galaxy clusters at 0.9<z<1.5, we obtain a twofold improvement in the efficiency of finding SNe compared to an HST field survey and a factor of three improvement in the total yield of SN detections in relatively dust-free red-sequence galaxies. In total, sixteen SNe were discovered at z>0.95, nine of which were in galaxy clusters. This strategy provides a SN sample that can be used to decouple the effects of host galaxy extinction and intrinsic color in high redshift SNe, thereby reducing one of the largest systematic uncertainties in SN cosmology. Comment: 15 pages, 8 figures, accepted by AJ, see http://www.supernova.lbl.gov for additional information pertaining to the HST Cluster SN Survey
08/2009;
-
R. A. Knop,
G. Aldering,
R. Amanullah,
P. Astier,
G. Blanc,
M. S. Burns,
A. Conley,
S. E. Deustua, M. Doi,
R. Ellis, [......],
K. Schahmaneche,
E. Smith,
A. L. Spadafora,
V. Stanishev,
M. Sullivan,
N. A. Walton,
L. Wang,
W. M. Wood-Vasey,
N. Yasuda,
and (The Supernova Cosmology Project
[show abstract]
[hide abstract]
ABSTRACT: We report measurements of ΩM, ΩΛ, and w from 11 supernovae (SNe) at z = 0.36-0.86 with high-quality light curves measured using WFPC2 on the Hubble Space Telescope (HST). This is an independent set of high-redshift SNe that confirms previous SN evidence for an accelerating universe. The high-quality light curves available from photometry on WFPC2 make it possible for these 11 SNe alone to provide measurements of the cosmological parameters comparable in statistical weight to the previous results. Combined with earlier Supernova Cosmology Project data, the new SNe yield a measurement of the mass density ΩM = 0.25 (statistical) ± 0.04 (identified systematics), or equivalently, a cosmological constant of ΩΛ = 0.75 (statistical) ± 0.04 (identified systematics), under the assumptions of a flat universe and that the dark energy equation-of-state parameter has a constant value w = -1. When the SN results are combined with independent flat-universe measurements of ΩM from cosmic microwave background and galaxy redshift distortion data, they provide a measurement of w = -1.05 (statistical) ± 0.09 (identified systematic), if w is assumed to be constant in time. In addition to high-precision light-curve measurements, the new data offer greatly improved color measurements of the high-redshift SNe and hence improved host galaxy extinction estimates. These extinction measurements show no anomalous negative E(B-V) at high redshift. The precision of the measurements is such that it is possible to perform a host galaxy extinction correction directly for individual SNe without any assumptions or priors on the parent E(B-V) distribution. Our cosmological fits using full extinction corrections confirm that dark energy is required with P(ΩΛ > 0) > 0.99, a result consistent with previous and current SN analyses that rely on the identification of a low-extinction subset or prior assumptions concerning the intrinsic extinction distribution.
The Astrophysical Journal 12/2008; 598(1):102. · 6.02 Impact Factor
-
Bianca M. Poggianti,
Terry J. Bridges,
Dave Carter,
Bahram Mobasher, M. Doi,
M. Iye,
N. Kashikawa,
Y. Komiyama,
S. Okamura,
M. Sekiguchi,
K. Shimasaku,
M. Yagi,
and N. Yasuda
[show abstract]
[hide abstract]
ABSTRACT: The ages of stellar populations in 52 elliptical and S0 galaxies in the Coma Cluster are investigated, using a new spectroscopic sample. More than 40% of the S0's are found to have undergone star formation in their central regions during the last ~5 Gyr, while such activity is absent in the ellipticals. Galaxies in this sample have absolute magnitudes in the range -20.5 < MB < -17.5, and the fraction of S0 galaxies with recent star formation is higher at fainter luminosities. The observed luminosity range of S0 galaxies with signs of recent star formation activity is consistent with them being the descendants of typical star-forming spirals at intermediate redshift whose star formation has been halted as a consequence of the dense environment.
The Astrophysical Journal 12/2008; 563(1):118. · 6.02 Impact Factor
-
T. Nagao,
Y. Taniguchi,
N. Kashikawa,
K. Kodaira,
N. Kaifu,
H. Ando,
H. Karoji,
M. Ajiki,
M. Akiyama,
K. Aoki, [......],
Y. Sato,
K. Sekiguchi,
K. Shimasaku,
Y. Shioya,
H. Tamura,
I. Tanaka,
M. Umemura,
T. Yamada,
N. Yasuda,
and M. Yoshida
[show abstract]
[hide abstract]
ABSTRACT: We report on the discovery of a star-forming galaxy at z = 6.33 in the Subaru Deep Field. This object is selected as a candidate of an i'-dropout high-redshift galaxy around z = 6 because of its red i' - z' color in our deep optical imaging survey in the Subaru Deep Field. Our follow-up optical spectroscopy reveals that this object is a strong Lyα emitter with only very faint ultraviolet continuum. The rest-frame equivalent width of the detected Lyα emission is as much as 130 Å. Thus the light detected in our z' image is largely attributed to the Lyα emission, i.e., ~40% of the z'-band flux is the strong Lyα emission, giving a very red i' - z' color. This is consistent with the photometric property of this object because the narrowband data obtained with the NB921 filter show a significant depression, z' - NB921 = -0.54 mag. By using the photometric data, we show that some other objects among the 48 i'-dropout high-redshift galaxy candidates found in the Subaru Deep Field also show a significant NB921 depression. We briefly discuss the nature of these NB921-depressed objects.
The Astrophysical Journal 12/2008; 613(1):L9. · 6.02 Impact Factor
-
Bahram Mobasher,
Terry J. Bridges,
Dave Carter,
Bianca M. Poggianti,
Y. Komiyama,
N. Kashikawa, M. Doi,
M. Iye,
S. Okamura,
M. Sekiguchi,
K. Shimasaku,
M. Yagi,
and N. Yasuda
[show abstract]
[hide abstract]
ABSTRACT: This is the second paper in a series studying the photometric and spectroscopic properties of galaxies of different luminosities in the Coma Cluster. We present the sample selection, spectroscopic observations, and completeness functions. To study the spectral properties of galaxies as a function of their local environment, two fields were selected for spectroscopic observations to cover both the core (Coma 1) and outskirts (i.e., southwest of the core and centered on NGC 4839; Coma 3) of the cluster. To maximize the efficiency of spectroscopic observations, two subsamples were defined, consisting of "bright" and "faint" galaxies, both drawn from magnitude-limited parent samples. Medium-resolution spectroscopy (6-9 Å) was then carried out for a total of 490 galaxies in both fields (302 in Coma 1 and 188 in Coma 3), using the WYFFOS multifiber spectrograph on the William Herschel Telescope. The galaxies cover a range of 12 < R < 20, corresponding to -23 < MR < -15 (H0 = 65 km s-1 Mpc-1). The redshifts for these galaxies are measured with an accuracy of 75 km s-1. The spectral line strengths and equivalent widths are also measured for the same galaxies and analyzed in the next paper of this series. A total of 189 (Coma 1) and 90 (Coma 3) galaxies are identified as members of the Coma Cluster. An analysis of the colors show that only two members of the Coma Cluster in our sample have B - R > 2. The completeness functions for our sample are calculated. These show that the bright sample is 65% complete at R < 17 mag, becoming increasingly incomplete toward fainter magnitudes, while the faint sample follows a monotonically decreasing completeness function at R > 19 mag.
The Astrophysical Journal Supplement Series 12/2008; 137(2):279. · 13.46 Impact Factor
-
David Carter,
Bahram Mobasher,
Terry J. Bridges,
Bianca M. Poggianti,
Y. Komiyama,
N. Kashikawa, M. Doi,
M. Iye,
S. Okamura,
M. Sekiguchi,
K. Shimasaku,
M. Yagi,
and N. Yasuda
[show abstract]
[hide abstract]
ABSTRACT: We investigate the radial dependence of the spectroscopic properties, in particular the Mg2, Fe, and Hβ spectroscopic indices, in a sample of galaxies spanning a wide range of absolute luminosity in the Coma Cluster. After allowing for the magnitude dependence of these indices, we find a significant gradient in Mg2, in the sense that galaxies in the core of the cluster have stronger Mg2. We find only weak gradients in Fe and Hβ. Using the model grids presented in an earlier paper in this series, we attribute the Mg2 gradient to changes in metal abundance. One possible mechanism to create this abundance gradient is pressure confinement by the intracluster medium of material from supernova-driven winds early in the history of the galaxies.
The Astrophysical Journal 12/2008; 567(2):772. · 6.02 Impact Factor
-
Bianca M. Poggianti,
Terry J. Bridges,
Bahram Mobasher,
Dave Carter, M. Doi,
M. Iye,
N. Kashikawa,
Y. Komiyama,
S. Okamura,
M. Sekiguchi,
K. Shimasaku,
M. Yagi,
and N. Yasuda
[show abstract]
[hide abstract]
ABSTRACT: We present a detailed analysis of the spectroscopic catalog of galaxies in the Coma Cluster from Mobasher et al. (Paper II of the series). This catalog comprises ~300 spectra of cluster members with absolute magnitudes in the range MB = -20.5 to -14 in two areas of ~1 × 1.5 Mpc toward the center and the southwest region of the cluster. In order to study the star formation and metallicity properties of the Coma galaxies as a function of their luminosity and environment, spectral indices of the Lick/IDS system and equivalent widths of the emission lines were measured in the range λ = 3600-6600 Å. In this paper, the analysis is restricted to the 257 galaxies with no emission lines in their spectra. The strength of the age-sensitive indices (such as Hβ, HγF, and HδF) is found to correlate with galaxy magnitude over the whole magnitude range explored in this study. Similarly, the metallicity-sensitive indices (such as Mg2, Fe, and C24668) anticorrelate with magnitude. By comparing the observed indices with model grids based on the Padova isochrones, we derive luminosity-weighted ages and metallicities. We present the distributions of ages and metallicities for galaxies in various magnitude bins. The mean metallicity decreases with galaxy magnitude and, at a given luminosity, appears to be generally lower for galaxies in the southwest region of Coma as compared to the center of the cluster. A broad range of ages, from younger than 3 Gyr to older than 9 Gyr, is found in galaxies of any magnitude. However, systematic trends of age with luminosity are present among galaxies in the central field, including a slight decrease of the mean age for fainter galaxies. Furthermore, in the central Mpc of Coma, a large fraction of galaxies at any luminosity (50%-60% of the giants, more than 30% of the dwarfs) show no evidence in their central regions of star formation occurred at redshift z < 2, while the proportion of galaxies with significant star formation occurring at intermediate (0.35 < z < 2) and low (z < 0.35) redshifts is found to depend on galaxy luminosity. An additional surprising result is that the faint galaxies with young luminosity-weighted ages appear to have a bimodal metallicity distribution that, if confirmed, would point to a composite formation scenario involving different physical processes. Coadding the spectra of these metal-rich and metal-poor galaxies separately supports the reality of the metallicity bimodality, although higher signal-to-noise ratio spectra of the individual galaxies will be needed to draw definite conclusions. An anticorrelation between age and metallicity is found to be present in galaxies of any given luminosity bin, and it is especially evident among the brightest subset with the highest signal-to-noise ratio spectra. Finally, we present an interpretation of the index-magnitude relations observed. We show that the slopes of the indices/magnitude relations are the consequence of both age and metallicity trends with luminosity: each such trend on its own would be sufficient to produce relations similar to those observed.
The Astrophysical Journal 12/2008; 562(2):689. · 6.02 Impact Factor
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K. Shimasaku,
M. Ouchi,
S. Okamura,
N. Kashikawa, M. Doi,
H. Furusawa,
M. Hamabe,
T. Hayashino,
K. Kawabata,
M. Kimura, [......],
F. Nakata,
K. Ohta,
Y. Ohyama,
M. Sekiguchi,
Y. Shioya,
H. Tamura,
Y. Taniguchi,
M. Yagi,
T. Yamada,
and N. Yasuda
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ABSTRACT: We report the discovery of a large-scale structure of Lyα emitters (LAEs) at z = 4.86 based on wide-field imaging with the prime-focus camera (Suprime-Cam) on the Subaru Telescope. We observed a 25' × 45' area of the Subaru Deep Field in a narrow band (NB711, λc = 7126 Å and FWHM = 73 Å) together with R and i'. We isolate from these data 43 LAE candidates down to NB711 = 25.5 mag using color criteria. Follow-up spectroscopy of five candidates suggests the contamination by low-z objects to be ~20%. We find that the LAE candidates are clustered in an elongated region on the sky of 20 Mpc in width and 50 Mpc in length at z = 4.86, which is comparable in size to present-day large-scale structures (we adopt H0 = 70 km s-1 Mpc-1, Ω0 = 0.3, and λ0 = 0.7). This elongated region includes a circular region of 12 Mpc radius of higher surface overdensity (δΣ = 2), which may be the progenitor of a cluster of galaxies. Assuming this circular region to be a sphere with a spatial overdensity of 2, we compare our observation with predictions by cold dark matter models. We find that an Ω0 = 0.3 flat model with σ8 = 0.9 predicts the number of such spheres consistent with the observed number (one sphere in our survey volume) if the bias parameter of LAEs is b 6. This value suggests that the typical mass of dark halos hosting LAEs at z 5 is of the order of 1012 M☉. Such a large mass poses an interesting question about the nature of LAEs.
The Astrophysical Journal 12/2008; 586(2):L111. · 6.02 Impact Factor
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Y. Komiyama,
M. Sekiguchi,
N. Kashikawa,
M. Yagi, M. Doi,
M. Iye,
S. Okamura,
K. Shimasaku,
N. Yasuda,
B. Mobasher,
D. Carter,
T. J. Bridges,
and B. M. Poggianti
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ABSTRACT: We carried out a deep photometric and spectroscopic survey of wide areas in the Coma cluster, aiming to investigate the properties of galaxy population in different environments within the cluster. We present the results in a series of papers. This paper, the first of the series, describes the imaging observations and photometric data reduction. Imaging data were taken with the wide-field mosaic CCD camera, which was attached to the prime focus of the 4.2 m William Herschel Telescope at La Palma, Canary Islands. Our observations covered a large field of view (2.22 deg2) from the cluster center to the outskirts, and our photometry is complete to a limiting magnitude of R 23 mag. The limit of secure star-galaxy discrimination is, however, brighter at R = 20 mag. We identified 3147 galaxies down to this limit in the part (1.32 deg2) of the survey area, together with 662 galaxies identified in the control field SA 57. We measured surface photometric parameters and compiled a photometric catalog for these galaxies. Statistical properties of the catalog are shown in this paper, while the catalog itself is given in a forthcoming paper in the series.
The Astrophysical Journal Supplement Series 12/2008; 138(2):265. · 13.46 Impact Factor
