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David P. Palamara,
Michael J. I. Brown,
Buell T. Jannuzi,
Arjun Dey,
Daniel Stern,
Kevin A. Pimbblet,
Benjamin J. Weiner,
Matthew L. N. Ashby,
C. S. Kochanek,
Anthony Gonzalez, Mark Brodwin,
Emeric Le Floc'h,
Marcia Rieke
[show abstract]
[hide abstract]
ABSTRACT: We measure the clustering of Extremely Red Objects (EROs) in ~8 deg^2 of the
NOAO Deep Wide Field Survey Bo\"otes field in order to establish robust links
between ERO z~1.2 and local galaxy z<0.1 populations. Three different color
selection criteria from the literature are analyzed to assess the consequences
of using different criteria for selecting EROs. Specifically, our samples are
(R-K_s)>5.0 (28,724 galaxies), (I-K_s)>4.0 (22,451 galaxies) and (I-[3.6])>5.0
(64,370 galaxies). Magnitude-limited samples show the correlation length (r_0)
to increase for more luminous EROs, implying a correlation with stellar mass.
We can separate star-forming and passive ERO populations using the (K_s-[24])
and ([3.6]-[24]) colors to K_s=18.4 and [3.6]=17.5, respectively. Star-forming
and passive EROs in magnitude limited samples have different clustering
properties and host dark halo masses, and cannot be simply understood as a
single population. Based on the clustering, we find that bright passive EROs
are the likely progenitors of >4L^* elliptical galaxies. Bright EROs with
ongoing star formation were found to occupy denser environments than
star-forming galaxies in the local Universe, making these the likely
progenitors of >L^* local ellipticals. This suggests that the progenitors of
massive >4L^* local ellipticals had stopped forming stars by z>1.2, but that
the progenitors of less massive ellipticals (down to L^*) can still show
significant star formation at this epoch.
11/2012;
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[show abstract]
[hide abstract]
ABSTRACT: We measure the faint end slope of the galaxy luminosity function (LF) for
cluster galaxies at 1<z<1.5 using Spitzer IRAC data. We investigate whether
this slope, alpha, differs from that of the field LF at these redshifts, and
with the cluster LF at low redshifts. The latter is of particular interest as
low-luminosity galaxies are expected to undergo significant evolution. We use
seven high-redshift spectroscopically confirmed galaxy clusters drawn from the
IRAC Shallow Cluster Survey to measure the cluster galaxy LF down to depths of
M* + 3 (3.6 microns) and M* + 2.5 (4.5 microns). The summed LF at our median
cluster redshift (z=1.35) is well fit by a Schechter distribution with
alpha[3.6] = -0.97 +/- 0.14 and alpha[4.5] = -0.91 +/- 0.28, consistent with a
flat faint end slope and is in agreement with measurements of the field LF in
similar bands at these redshifts. A comparison to alpha in low-redshift
clusters finds no statistically significant evidence of evolution. Combined
with past studies which show that M* is passively evolving out to z~1.3, this
means that the shape of the cluster LF is largely in place by z~1.3. This
suggests that the processes that govern the build up of the mass of low-mass
cluster galaxies have no net effect on the faint end slope of the cluster LF at
z<1.3.
11/2012;
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Caty Pilachowski,
Carles Badenes,
Stephen Bailey,
Aaron Barth,
Rachel Beaton,
Eric Bell,
Rebecca Bernstein,
Fuyan Bian,
Michael Blanton,
Robert Blum, [......],
Daniel Stern,
Lisa Storrie-Lombardi,
Nicholas Suntzeff,
Jason Surace,
Alex Szalay,
Melville Ulmer,
Ben Weiner,
Beth Willman,
Rogier Windhorst,
Michael Wood-Vasey
[show abstract]
[hide abstract]
ABSTRACT: This document summarizes the results of a community-based discussion of the
potential science impact of the Mayall+BigBOSS highly multiplexed multi-object
spectroscopic capability. The KPNO Mayall 4m telescope equipped with the DOE-
and internationally-funded BigBOSS spectrograph offers one of the most
cost-efficient ways of accomplishing many of the pressing scientific goals
identified for this decade by the "New Worlds, New Horizons" report. The
BigBOSS Key Project will place unprecedented constraints on cosmological
parameters related to the expansion history of the universe. With the addition
of an open (publicly funded) community access component, the scientific impact
of BigBOSS can be extended to many important astrophysical questions related to
the origin and evolution of galaxies, stars, and the IGM. Massive spectroscopy
is the critical missing ingredient in numerous ongoing and planned ground- and
space-based surveys, and BigBOSS is unique in its ability to provide this to
the US community. BigBOSS data from community-led projects will play a vital
role in the education and training of students and in maintaining US leadership
in these fields of astrophysics. We urge the NSF-AST division to support
community science with the BigBOSS multi-object spectrograph through the period
of the BigBOSS survey in order to ensure public access to the extraordinary
spectroscopic capability.
11/2012;
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Roberto J. Assef,
Daniel Stern,
Christopher S. Kochanek,
Andrew W. Blain, Mark Brodwin,
Michael J. I. Brown,
Emilio Donoso,
Peter R. M. Eisenhardt,
Buell T. Jannuzi,
Thomas H. Jarrett,
S. Adam Stanford,
Chao-Wei Tsai,
Jingwen Wu,
Lin Yan
[show abstract]
[hide abstract]
ABSTRACT: Stern et al.(2012) presented a study of WISE selection of AGN in the 2 deg^2
COSMOS field, finding that a simple criterion W1-W2>=0.8 provides a highly
reliable and complete AGN sample for W2<15.05, where the W1 and W2 passbands
are centered at 3.4 and 4.6 microns, respectively. Here we extend this study
using the larger 9 deg^2 NOAO Deep Wide-Field Survey Bootes field which also
has considerably deeper WISE observations than the COSMOS field, and find that
this simple color-cut significantly loses reliability at fainter fluxes. We
define a modified selection criterion combining the W1-W2 color and the W2
magnitude to provide highly reliable or highly complete AGN samples for fainter
WISE sources. In particular, we define a color-magnitude cut that finds 130+/-4
deg^-2 AGN candidates for W2<17.11 with 90% reliability. Using the extensive UV
through mid-IR broad-band photometry available in this field, we study the
spectral energy distributions of WISE AGN candidates. As expected, the WISE AGN
selection is biased towards objects where the AGN dominates the bolometric
luminosity output, and that it can identify highly obscured AGN. We study the
distribution of reddening in the AGN sample and discuss a formalism to account
for sample incompleteness based on the step-wise maximum-likelihood method of
Efstathiou et al.(1988). The resulting dust obscuration distributions depend
strongly on AGN luminosity, consistent with the trend expected for a Simpson
(2005) receding torus. At L_AGN~3x10^44 erg/s, 29+/-7% of AGN are observed as
Type 1, while at ~4x10^45 erg/s the fraction is 64+/-13%. The distribution of
obscuration values suggests that dust in the torus is present as both a diffuse
medium and in optically thick clouds.
09/2012;
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[show abstract]
[hide abstract]
ABSTRACT: We report the discovery of an IR-selected galaxy cluster in the IRAC Distant
Cluster Survey (IDCS). New data from the Hubble Space Telescope
spectroscopically confirm IDCS J1433.2+3306 at z = 1.89 with robust
spectroscopic redshifts for seven members, two of which are based on the 4000
Angstrom break. Detected emission lines such as [OII] and Hbeta indicate star
formation rates of >20 solar masses per year for three galaxies within a 500
kpc projected radius of the cluster center. The cluster exhibits a red sequence
with a scatter and color indicative of a formation redshift z > 3.5. The
stellar age of the early-type galaxy population is approximately consistent
with those of clusters at lower redshift (1 < z < 1.5) suggesting that clusters
at these redshifts are experiencing ongoing or increasing star formation.
07/2012;
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Gregory F. Snyder, Mark Brodwin,
Conor M. Mancone,
Gregory R. Zeimann,
S. A. Stanford,
Anthony H. Gonzalez,
Daniel Stern,
Peter R. M. Eisenhardt,
Michael J. I. Brown,
Arjun Dey,
Buell Jannuzi,
Saul Perlmutter
[show abstract]
[hide abstract]
ABSTRACT: We present results for the assembly and star formation histories of massive
(~L*) red sequence galaxies in 11 spectroscopically confirmed,
infrared-selected galaxy clusters at 1.0 < z < 1.5, the precursors to
present-day massive clusters with M ~ 10^15 M_sun. Using rest-frame optical
photometry, we investigate evolution in the color and scatter of the red
sequence galaxy population, comparing with models of possible star formation
histories. In contrast to studies of central cluster galaxies at lower redshift
(z < 1), these data are clearly inconsistent with the continued evolution of
stars formed and assembled primarily at a single, much-earlier time.
Specifically, we find that the colors of massive cluster galaxies at z = 1.5
imply that the bulk of star formation occurred at z ~ 3, whereas by z = 1 their
colors imply formation at z ~ 2; therefore these galaxies exhibit approximately
the same luminosity-weighted stellar age at 1 < z < 1.5. This likely reflects
star formation that occurs over an extended period, the effects of significant
progenitor bias, or both. Our results generally indicate that massive cluster
galaxy populations began forming a significant mass of stars at z >~ 4,
contained some red spheroids by z ~ 1.5, and were actively assembling much of
their final mass during 1 < z < 2 in the form of younger stars. Qualitatively,
the slopes of the cluster color-magnitude relations are consistent with no
significant evolution relative to local clusters.
07/2012;
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Daniel P. Gettings,
Anthony H. Gonzalez,
S. Adam Stanford,
Peter R. M. Eisenhardt, Mark Brodwin,
Conor Mancone,
Daniel Stern,
Gregory R. Zeimann,
Frank J. Masci,
Casey Papovich,
Ichi Tanaka,
Edward L. Wright
[show abstract]
[hide abstract]
ABSTRACT: We present spectroscopic confirmation of a z=0.99 galaxy cluster discovered
using data from the Wide-field Infrared Survey Explorer (WISE). This is the
first z~1 cluster candidate from the Massive Distant Clusters of WISE Survey
(MaDCoWS) to be confirmed. It was selected as an overdensity of probable z>~1
sources using a combination of WISE and SDSS-DR8 photometric catalogs. Deeper
follow-up imaging data from Subaru and WIYN reveal the cluster to be a rich
system of galaxies, and multi-object spectroscopic observations from Keck
confirm five cluster members at z=0.99. The detection and confirmation of this
cluster represents a first step towards constructing a uniformly-selected
sample of distant, high-mass galaxy clusters over the full extragalactic sky
using WISE data.
05/2012;
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[show abstract]
[hide abstract]
ABSTRACT: The galaxy cluster IDCS J1426.5+3508 at z = 1.75 is the most massive galaxy
cluster yet discovered at z > 1.4 and the first cluster at this epoch for which
the Sunyaev-Zel'Dovich effect has been observed. In this paper we report on the
discovery with HST imaging of a giant arc associated with this cluster. The
curvature of the arc suggests that the lensing mass is nearly coincident with
the brightest cluster galaxy, and the color is consistent with the arc being a
star-forming galaxy. We compare the constraint on M200 based upon strong
lensing with Sunyaev-Zel'Dovich results, finding that the two are consistent if
the redshift of the arc is z > 3. Finally, we explore the cosmological
implications of this system, considering the likelihood of the existence of a
strongly lensing galaxy cluster at this epoch in an LCDM universe. While the
existence of the cluster itself can potentially be accomodated if one considers
the entire volume covered at this redshift by all current high-redshift cluster
surveys, the existence of this strongly lensed galaxy greatly exacerbates the
long-standing giant arc problem. For standard LCDM structure formation and
observed background field galaxy counts this lens system should not exist.
Specifically, there should be no giant arcs in the entire sky as bright in
F814W as the observed arc for clusters at z \geq 1.75, and only \sim 0.3 as
bright in F160W as the observed arc. If we relax the redshift constraint to
consider all clusters at z \geq 1.5, the expected number of giant arcs rises to
\sim15 in F160W, but the number of giant arcs of this brightness in F814W
remains zero. These arc statistic results are independent of the mass of IDCS
J1426.5+3508. We consider possible explanations for this discrepancy.
05/2012;
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Jeff Wagg,
Alexandra Pope,
Stacey Alberts,
Lee Armus, Mark Brodwin,
Robert S. Bussmann,
Vandana Desai,
Arjun Dey,
Buell Jannuzi,
Emeric Le Floc'h,
Jason Melbourne,
Daniel Stern
[show abstract]
[hide abstract]
ABSTRACT: We present observations of CO J=2-1 line emission in infrared-luminous
cluster galaxies at z~1 using the IRAM Plateau de Bure Interferometer. Our two
primary targets are optically faint, dust-obscured galaxies (DOGs) found to lie
within 2 Mpc of the centers of two massive (>10^14 Msun) galaxy clusters. CO
line emission is not detected in either DOG. We calculate 3-sigma upper limits
to the CO J=2-1 line luminosities, L'_CO < 6.08x10^9 and < 6.63x10^9 K km/s
pc^2. Assuming a CO-to-H_2 conversion factor derived for ultraluminous infrared
galaxies in the local Universe, this translates to limits on the cold molecular
gas mass of M_H_2 < 4.86x10^9 Msun and M_H_2 < 5.30x10^9 Msun. Both DOGs
exhibit mid-infrared continuum emission that follows a power-law, suggesting
that an AGN contributes to the dust heating. As such, estimates of the star
formation efficiencies in these DOGs are uncertain. A third cluster member with
an infrared luminosity, L_IR < 7.4x10^11 Lsun, is serendipitously detected in
CO J=2-1 line emission in the field of one of the DOGs located roughly two
virial radii away from the cluster center. The optical spectrum of this object
suggests that it is likely an obscured AGN, and the measured CO line luminosity
is L'_CO = (1.94 +/- 0.35)x10^10 K km/s pc^2, which leads to an estimated cold
molecular gas mass M_H_2 = (1.55+/-0.28)x10^10 Msun. A significant reservoir of
molecular gas in a z~1 galaxy located away from the cluster center demonstrates
that the fuel can exist to drive an increase in star-formation and AGN activity
at the outskirts of high-redshift clusters.
04/2012;
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Moire K. M. Prescott,
Arjun Dey, Mark Brodwin,
Frederic H. Chaffee,
Vandana Desai,
Peter Eisenhardt,
Emeric Le Floc'h,
Buell T. Jannuzi,
Nobunari Kashikawa,
Yuichi Matsuda,
B. T. Soifer
[show abstract]
[hide abstract]
ABSTRACT: Detailed analysis of the substructure of Lya nebulae can put important
constraints on the physical mechanisms at work and the properties of galaxies
forming within them. Using high resolution HST imaging of a Lya nebula at
z~2.656, we have taken a census of the compact galaxies in the vicinity, used
optical/near-infrared colors to select system members, and put constraints on
the morphology of the spatially-extended emission. The system is characterized
by (a) a population of compact, low luminosity (~0.1 L*) sources --- 17
primarily young, small (Re~1-2 kpc), disky galaxies including an obscured AGN
--- that are all substantially offset (>20 kpc) from the line-emitting nebula;
(b) the lack of a central galaxy at or near the peak of the Lya emission; and
(c) several nearly coincident, spatially extended emission components --- Lya,
HeII, and UV continuum --- that are extremely smooth. These morphological
findings are difficult to reconcile with theoretical models that invoke
outflows, cold flows, or resonant scattering, suggesting that while all of
these physical phenomena may be occurring, they are not sufficient to explain
the powering and large extent of Lya nebulae. In addition, although the compact
galaxies within the system are irrelevant as power sources, the region is
significantly overdense relative to the field galaxy population (by at least a
factor of 4). These observations provide the first estimate of the luminosity
function of galaxies within an individual Lya nebula system, and suggest that
large Lya nebulae may be the seeds of galaxy groups or low-mass clusters.
11/2011;
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[show abstract]
[hide abstract]
ABSTRACT: We present results from a systematic study of star formation in local galaxy
clusters using 22 micron data from the Wide-field Infrared Survey Explorer
(WISE). The 69 systems in our sample are drawn from the Cluster Infall Regions
Survey (CIRS), and all have robust mass determinations. The all-sky WISE data
enables us to quantify the amount of star formation, as traced by 22 micron, as
a function of radius well beyond R200, and investigate the dependence of total
star formation rate upon cluster mass. We find that the fraction of
star-forming galaxies increases with cluster radius but remains below the field
value even at 3 R200. We also find that there is no strong correlation between
the mass-normalized total specific star formation rate and cluster mass,
indicating that the mass of the host cluster does not strongly influence the
total star formation rate of cluster members.
08/2011;
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Kyoung-Soo Lee,
Arjun Dey,
Naveen Reddy,
Michael J. I. Brown,
Anthony H. Gonzalez,
Buell T. Jannuzi,
Michael C. Cooper,
Xiaohui Fan,
Fuyan Bian,
Eilat Glikman,
Daniel Stern, Mark Brodwin,
and Asantha Cooray
[show abstract]
[hide abstract]
ABSTRACT: We investigate the average physical properties and star formation histories (SFHs) of the most UV-luminous star-forming galaxies at z ~ 3.7. Our results are based on the average spectral energy distributions (SEDs), constructed from stacked optical-to-infrared photometry, of a sample of the 1913 most UV-luminous star-forming galaxies found in 5.3 deg2 of the NOAO Deep Wide-Field Survey. We find that the shape of the average SED in the rest optical and infrared is fairly constant with UV luminosity, i.e., more UV-luminous galaxies are, on average, also more luminous at longer wavelengths. In the rest UV, however, the spectral slope β (≡ dlogF λ/dlogλ; measured at 0.13 μm < λrest < 0.28 μm) rises steeply with the median UV luminosity from –1.8 at L L* to –1.2 (L 4-5L*). We use population synthesis analyses to derive their average physical properties and find that (1) L UV and thus star formation rates (SFRs) scale closely with stellar mass such that more UV-luminous galaxies are also more massive, (2) the median ages indicate that the stellar populations are relatively young (200-400 Myr) and show little correlation with UV luminosity, and (3) more UV-luminous galaxies are dustier than their less-luminous counterparts, such that L 4-5L* galaxies are extincted up to A(1600) = 2 mag while L L* galaxies have A(1600) = 0.7-1.5 mag. We argue that the average SFHs of UV-luminous galaxies are better described by models in which SFR increases with time in order to simultaneously reproduce the tight correlation between the UV-derived SFR and stellar mass and their universally young ages. We demonstrate the potential of measurements of the SFR-M * relation at multiple redshifts to discriminate between simple models of SFHs. Finally, we discuss the fate of these UV-brightest galaxies in the next 1-2 Gyr and their possible connection to the most massive galaxies at z ~ 2.
The Astrophysical Journal 05/2011; 733(2):99. · 6.02 Impact Factor
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Ryan C. Hickox,
Adam D. Myers, Mark Brodwin,
David M. Alexander,
William R. Forman,
Christine Jones,
Stephen S. Murray,
Michael J. I. Brown,
Richard J. Cool,
Christopher S. Kochanek, [......],
Buell T. Jannuzi,
Daniel Eisenstein,
Roberto J. Assef,
Peter R. Eisenhardt,
Varoujan Gorjian,
Daniel Stern,
Emeric Le Floc'h,
Nelson Caldwell,
Andrew D. Goulding,
and James R. Mullaney
[show abstract]
[hide abstract]
ABSTRACT: We present the first measurement of the spatial clustering of mid-infrared-selected obscured and unobscured quasars, using a sample in the redshift range 0.7 < z < 1.8 selected from the 9 deg2 Boötes multiwavelength survey. Recently, the Spitzer Space Telescope and X-ray observations have revealed large populations of obscured quasars that have been inferred from models of the X-ray background and supermassive black hole evolution. To date, little is known about obscured quasar clustering, which allows us to measure the masses of their host dark matter halos and explore their role in the cosmic evolution of black holes and galaxies. In this study, we use a sample of 806 mid-infrared-selected quasars and 250,000 galaxies to calculate the projected quasar-galaxy cross-correlation function wp (R). The observed clustering yields characteristic dark matter halo masses of log(M halo [h –1 M ☉]) = 12.7+0.4 –0.6 and 13.3+0.3 –0.4 for unobscured quasars (QSO-1s) and obscured quasars (Obs-QSOs), respectively. The results for QSO-1s are in excellent agreement with previous measurements for optically selected quasars, while we conclude that the Obs-QSOs are at least as strongly clustered as the QSO-1s. We test for the effects of photometric redshift errors on the optically faint Obs-QSOs, and find that our method yields a robust lower limit on the clustering; photo-z errors may cause us to underestimate the clustering amplitude of the Obs-QSOs by at most ~20%. We compare our results to previous studies, and speculate on physical implications of stronger clustering for obscured quasars.
The Astrophysical Journal 03/2011; 731(2):117. · 6.02 Impact Factor
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Ryan C. Hickox,
Adam D. Myers, Mark Brodwin,
David M. Alexander,
William R. Forman,
Christine Jones,
Stephen S. Murray,
Michael J. I. Brown,
Richard J. Cool,
Roberto J. Assef, [......],
Arjun Dey,
Buell T. Jannuzi,
Daniel Eisenstein,
Peter R. Eisenhardt,
Varoujan Gorjian,
Daniel Stern,
Emeric Le Floc'h,
Nelson Caldwell,
Andrew D. Goulding,
James R. Mullaney
[show abstract]
[hide abstract]
ABSTRACT: We present the first measurement of the spatial clustering of mid-infrared
selected obscured and unobscured quasars, using a sample in the redshift range
0.7 < z < 1.8 selected from the 9 deg^2 Bootes multiwavelength survey. Recently
the Spitzer Space Telescope and X-ray observations have revealed large
populations of obscured quasars that have been inferred from models of the
X-ray background and supermassive black hole evolution. To date, little is
known about obscured quasar clustering, which allows us to measure the masses
of their host dark matter halos and explore their role in the cosmic evolution
of black holes and galaxies. In this study we use a sample of 806 mid-infrared
selected quasars and ~250,000 galaxies to calculate the projected quasar-galaxy
cross-correlation function w_p(R). The observed clustering yields
characteristic dark matter halo masses of log (M_halo [h^-1 M_sun]) =
12.7^+0.4_-0.6 and 13.3^+0.3_-0.4 for unobscured quasars (QSO-1s) and obscured
quasars (Obs-QSOs), respectively. The results for QSO-1s are in excellent
agreement with previous measurements for optically-selected quasars, while we
conclude that the Obs-QSOs are at least as strongly clustered as the QSO-1s. We
test for the effects of photometric redshift errors on the optically-faint
Obs-QSOs, and find that our method yields a robust lower limit on the
clustering; photo-z errors may cause us to underestimate the clustering
amplitude of the Obs-QSOs by at most ~20%. We compare our results to previous
studies, and speculate on physical implications of stronger clustering for
obscured quasars.
02/2011;
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Kyle Penner,
Alexandra Pope,
Edward L Chapin,
Thomas R Greve,
Frank Bertoldi, Mark Brodwin,
Ranga-Ram Chary,
Christopher J Conselice,
Kristen Coppin,
Mauro Giavalisco,
David H Hughes,
Rob J Ivison,
Thushara Perera,
Douglas Scott,
Kimberly Scott,
Grant Wilson,
Spitzer Fellow,
W M Keck,
Postdoctoral Fellow
[show abstract]
[hide abstract]
ABSTRACT: We present a study of the cosmic infrared background, which is a measure of the dust obscured activity in all galaxies in the Universe. We venture to isolate the galaxies responsible for the background at 1 mm; with spectroscopic and photometric redshifts we constrain the redshift distribution of these galaxies. We create a deep 1.16 mm map (σ ∼ 0.5 mJy) by combining the AzTEC 1.1 mm and MAMBO 1.2 mm datasets in GOODS-N. This combined map contains 41 secure detections, 13 of which are new. By averaging the 1.16 mm flux densities of individually undetected galaxies with 24 µm flux densities > 25 µJy, we resolve 31–45 per cent of the 1.16 mm background. Repeating our analysis on the SCUBA 850 µm map, we resolve a higher percentage (40–64 per cent) of the 850 µm background. A majority of the background resolved (attributed to individual galaxies) at both wavelengths comes from galaxies at z > 1.3. If the ratio of the resolved submillimeter to millimeter background is applied to a reasonable scenario for the origins of the unresolved submillimeter background, 60–88 per cent of the total 1.16 mm background comes from galaxies at z > 1.3.
Mon. Not. R. Astron. Soc. 10/2010; 000:0-0.
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Kyle Penner,
Alexandra Pope,
Edward L. Chapin,
Thomas R. Greve,
Frank Bertoldi, Mark Brodwin,
Ranga-Ram Chary,
Christopher J. Conselice,
Kristen Coppin,
Mauro Giavalisco,
David H. Hughes,
Rob J. Ivison,
Thushara Perera,
Douglas Scott,
Kimberly Scott,
Grant Wilson
[show abstract]
[hide abstract]
ABSTRACT: We present a study of the cosmic infrared background, which is a measure of the dust obscured activity in all galaxies in the Universe. We venture to isolate the galaxies responsible for the background at 1mm; with spectroscopic and photometric redshifts we constrain the redshift distribution of these galaxies. We create a deep 1.16mm map (sigma ~ 0.5mJy) by combining the AzTEC 1.1mm and MAMBO 1.2mm datasets in GOODS-N. This combined map contains 41 secure detections, 13 of which are new. By averaging the 1.16mm flux densities of individually undetected galaxies with 24um flux densities > 25uJy, we resolve 31--45 per cent of the 1.16mm background. Repeating our analysis on the SCUBA 850um map, we resolve a higher percentage (40--64 per cent) of the 850um background. A majority of the background resolved (attributed to individual galaxies) at both wavelengths comes from galaxies at z > 1.3. If the ratio of the resolved submillimeter to millimeter background is applied to a reasonable scenario for the origins of the unresolved submillimeter background, 60--88 per cent of the total 1.16mm background comes from galaxies at z > 1.3. Comment: 12 pages, 10 figures. Accepted by MNRAS. The combined map is publicly available at http://www.astro.umass.edu/~pope/goodsn_mm/
09/2010;
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Daniel Stern,
James G. Bartlett, Mark Brodwin,
Asantha Cooray,
Roc Cutri,
Arjun Dey,
Peter Eisenhardt,
Anthony Gonzalez,
Jason Kalirai,
Amy Mainzer,
Leonidas Moustakas,
Jason Rhodes,
S. Adam Stanford,
Edward L. Wright
[show abstract]
[hide abstract]
ABSTRACT: [NIRSS is one of three concepts that contributed to the Wide-Field Infrared Survey Telescope (WFIRST) mission advocated by the Decadal Survey.] Operating beyond the reaches of the Earth's atmosphere, free of its limiting absorption and thermal background, the Near-Infrared Sky Surveyor (NIRSS) will deeply map the entire sky at near-infrared wavelengths, thereby enabling new and fundamental discoveries ranging from the identification of extrasolar planets to probing the reionization epoch by identifying thousands of quasars at z>10. NIRSS will directly address the NASA scientific objective of studying cosmic origins by using a 1.5-meter telescope to reach full-sky 0.2 uJy (25.6 mag AB) sensitivities in four passbands from 1 to 4 microns in a 4-yr mission. At the three shorter passbands (1 - 2.5 microns), the proposed depth is comparable to the deepest pencil-beam surveys done to date and is 3000 times more sensitive than the only previous all-sky near-infrared survey, 2MASS. At the longest passband (3.5 micron), which is not feasible from the ground, NIRSS will be 500 times more sensitive than WISE. NIRSS fills a pivotal gap in our knowledge of the celestial sphere, is a natural complement to WISE, and is well matched to the next generation of deep (0.1 uJy), wide-area (>2 pi ster), ground-based optical surveys (LSST and Pan-Starrs). With the high thermal backgrounds of ground-based infrared observations, a near-infrared full sky survey at sub-uJy sensitivity is only feasible from space. Comment: A Response to the Astro2010 Request for Information by the Electromagnetic Observations from Space (EOS) Panel
08/2010;
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[show abstract]
[hide abstract]
ABSTRACT: We present composite 3.6 and 4.5 μm luminosity functions (LFs) for cluster galaxies measured from the Spitzer Deep, Wide-Field Survey for 0.3 < z < 2. We compare the evolution of m* for these LFs to models for passively evolving stellar populations to constrain the primary epoch of star formation in massive cluster galaxies. At low redshifts (z 1.3), our results agree well with models with no mass assembly and passively evolving stellar populations with a luminosity-weighted mean formation redshift zf = 2.4 assuming a Kroupa initial mass function (IMF). We conduct a thorough investigation of systematic biases that might influence our results, and estimate systematic uncertainties of Δzf = +0.16 –0.18 (model normalization), Δzf = +0.40 –0.05 (α), and Δzf = +0.30 –0.45 (choice of stellar population model). For a Salpeter-type IMF, the typical formation epoch is thus strongly constrained to be z ~ 2-3. Higher formation redshifts can only be made consistent with the data if one permits an evolving IMF that is bottom-light at high redshift, as suggested by van Dokkum. At high redshifts (z 1.3), we also witness a statistically significant (>5σ) disagreement between the measured LF and the continuation of the passive evolution model from lower redshifts. After considering potential systematic biases that might influence our highest redshift data points, we interpret the observed deviation as potential evidence for ongoing mass assembly at this epoch.
The Astrophysical Journal 08/2010; 720(1):284. · 6.02 Impact Factor
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Peter R. M. Eisenhardt,
Roger L. Griffith,
Daniel Stern,
Edward L. Wright,
Matthew L. N. Ashby, Mark Brodwin,
Michael J. I. Brown,
R. S. Bussmann,
Arjun Dey,
A. M. Ghez,
Eilat Glikman,
Anthony H. Gonzalez,
J. Davy Kirkpatrick,
Quinn Konopacky,
Amy Mainzer,
David Vollbach,
and Shelley A. Wright
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ABSTRACT: We have identified a sample of cool field brown dwarf candidates using IRAC data from the Spitzer Deep, Wide-Field Survey (SDWFS). The candidates were selected from 400,000 SDWFS sources with [4.5] ≤ 18.5 mag and were required to have [3.6] – [4.5] ≥ 1.5 and [4.5] – [8.0] ≤ 2.0 on the Vega system. The first color requirement selects objects redder than all but a handful of presently known brown dwarfs with spectral classes later than T7, while the second eliminates 14 probable reddened active galactic nuclei (AGNs). Optical detection of four of the remaining 18 sources implies they are likely also AGNs, leaving 14 brown dwarf candidates. For two of the brightest candidates (SDWFS J143524.44+335334.6 and SDWFS J143222.82+323746.5), the spectral energy distributions including near-infrared detections suggest a spectral class of ~T8. The proper motion is <025 yr–1, consistent with expectations for a luminosity-inferred distance of >70 pc. The reddest brown dwarf candidate (SDWFS J143356.62+351849.2) has [3.6] – [4.5] = 2.24 and H – [4.5] > 5.7, redder than any published brown dwarf in these colors, and may be the first example of the elusive Y-dwarf spectral class. Models from Burrows et al. predict that larger numbers of cool brown dwarfs should be found for a Chabrier mass function. Suppressing the model [4.5] flux by a factor of 2, as indicated by previous work, brings the Burrows models and observations into reasonable agreement. The recently launched Wide-field Infrared Survey Explorer will probe a volume ~40× larger and should find hundreds of brown dwarfs cooler than T7.
The Astronomical Journal 05/2010; 139(6):2455. · 4.03 Impact Factor
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Peter R. M. Eisenhardt,
Roger L. Griffith,
Daniel Stern,
Edward L. Wright,
Matthew L. N. Ashby, Mark Brodwin,
Michael J. I. Brown,
R. S. Bussmann,
Arjun Dey,
A. M. Ghez,
Eilat Glikman,
Anthony H. Gonzalez,
J. Davy Kirkpatrick,
Quinn Konopacky,
Amy Mainzer,
David Vollbach,
Shelley A. Wright
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ABSTRACT: We have identified a sample of cool field brown dwarf candidates using IRAC data from the Spitzer Deep, Wide-Field Survey (SDWFS). The candidates were selected from 400,000 SDWFS sources with [4.5] <= 18.5 mag and required to have [3.6]-[4.5] >= 1.5 and [4.5] - [8.0] <= 2.0 on the Vega system. The first color requirement selects objects redder than all but a handful of presently known brown dwarfs with spectral classes later than T7, while the second eliminates 14 probable reddened AGN. Optical detection of 4 of the remaining 18 sources implies they are likely also AGN, leaving 14 brown dwarf candidates. For two of the brightest candidates (SDWFS J143524.44+335334.6 and SDWFS J143222.82+323746.5), the spectral energy distributions including near-infrared detections suggest a spectral class of ~ T8. The proper motion is < 0.25 "/yr, consistent with expectations for a luminosity inferred distance of >70 pc. The reddest brown dwarf candidate (SDWFS J143356.62+351849.2) has [3.6] - [4.5]=2.24 and H - [4.5] > 5.7, redder than any published brown dwarf in these colors, and may be the first example of the elusive Y-dwarf spectral class. Models from Burrows et al. (2003) predict larger numbers of cool brown dwarfs should be found for a Chabrier (2003) mass function. Suppressing the model [4.5] flux by a factor of two, as indicated by previous work, brings the Burrows models and observations into reasonable agreement. The recently launched Wide-field Infrared Survey Explorer (WISE) will probe a volume ~40x larger and should find hundreds of brown dwarfs cooler than T7. Comment: 13 pages, 6 figures, accepted for publication in the June 2010 issue of The Astronomical Journal
04/2010;
