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[show abstract]
[hide abstract]
ABSTRACT: We measure the evolution of the stellar mass function (SMF) from z=0-1 using
multi-wavelength imaging and spectroscopic redshifts from the PRism
MUlti-object Survey (PRIMUS) and the Sloan Digital Sky Survey (SDSS). From
PRIMUS we construct an i<23 flux-limited sample of ~40,000 galaxies at
z=0.2-1.0 over five fields totaling ~5.5 deg^2, and from the SDSS we select
~170,000 galaxies at z=0.01-0.2 that we analyze consistently with respect to
PRIMUS to minimize systematic errors in our evolutionary measurements. We find
that the SMF of all galaxies evolves relatively little since z=1, although we
do find evidence for mass assembly downsizing; we measure a ~30% increase in
the number density of ~10^10 Msun galaxies since z~0.6, and a <10% change in
the number density of all >10^11 Msun galaxies since z~1. Dividing the sample
into star-forming and quiescent using an evolving cut in specific
star-formation rate, we find that the number density of ~10^10 Msun
star-forming galaxies stays relatively constant since z~0.6, whereas the
space-density of >10^11 Msun star-forming galaxies decreases by ~50% between
z~1 and z~0. Meanwhile, the number density of ~10^10 Msun quiescent galaxies
increases steeply towards low redshift, by a factor of ~2-3 since z~0.6, while
the number of massive quiescent galaxies remains approximately constant since
z~1. These results suggest that the rate at which star-forming galaxies are
quenched increases with decreasing stellar mass, but that the bulk of the
stellar mass buildup within the quiescent population occurs around ~10^10.8
Msun. In addition, we conclude that mergers do not appear to be a dominant
channel for the stellar mass buildup of galaxies at z<1, even among massive
(>10^11 Msun) quiescent galaxies.
01/2013;
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Tomotsugu Goto, Stephane Arnouts,
Matthew Malkan,
Toshinobu Takagi,
Hanae Inami,
Chris Pearson,
Takehiko Wada,
Hideo Matsuhara,
Chisato Yamauchi,
Tsutomu T. Takeuchi,
Takao Nakagawa,
Shinki Oyabu,
Daisuke Ishihara,
David B. Sanders,
Emeric Le Floc’h,
Hyung Mok Lee,
Woong-Seob Jeong,
Stephen Serjeant,
Chris Sedgwick
[show abstract]
[hide abstract]
ABSTRACT: By cross-correlating the AKARI all-sky survey in six infrared (IR) bands (9, 18, 65, 90, 140 and 160 μm) with the Sloan Digital Sky Survey (SDSS) galaxies, we identified 2357 IR galaxies with a spectroscopic redshift. This is not just one of the largest samples of local IR galaxies, but AKARI provides crucial far-IR (FIR) bands for accurately measuring the galaxy spectral energy distribution (SED) across the peak of the dust emission at > 100 μ m. By fitting modern IR SED models to the AKARI photometry, we measured the total infrared luminosity (LIR) of individual galaxies.Using this LIR, we constructed the luminosity functions (LF) of IR galaxies at a median redshift of z= 0.031. The LF agrees well with that at z= 0.0082 (the Revised Bright Galaxy Sample), showing smooth and continuous evolution towards higher redshift LFs measured in the AKARI North Ecliptic Pole (NEP) deep field. By integrating the IR LF weighted by LIR, we measured the local cosmic IR luminosity density of ΩIR= (3.8+5.8−1.2) × 108 L⊙ Mpc−3. We separate galaxies into active galactic nuclei (AGN), star-forming galaxies (SFG) and composite by using the [N ii]/Hα versus [O iii]/Hβ line ratios. The fraction of AGN shows a continuous increase with increasing LIR from 25 to 90 per cent at 9 < log LIR < 12.5. The SFRHα and show good correlations with LIR for SFG and AGN, respectively. The self-absorption-corrected Hα/Hβ ratio shows a weak increase with LIR with a substantial scatter. When we separate IR LFs into contributions from AGN and SFG, the AGN contribution becomes dominant at LIR > 1011 L⊙, coinciding with the break of both the SFG and AGN IR LFs. At LIR≤ 1011 L⊙, SFG dominates IR LFs. Only 1.1 ± 0.1 per cent of ΩIR is produced by luminous infrared galaxies (LIR > 1011 L⊙), and only 0.03 ± 0.01 per cent by ultraluminous infrared galaxies (LIR > 1012 L⊙) in the local Universe. Compared with high-redshift results from the AKARI NEP deep survey, we observed a strong evolution of ΩSFGIR∝ (1 +z)4.1±0.4 and ΩAGNIR∝ (1 +z)4.1±0.5. Our results show that all of our measured quantities (IR LFs, L*, ΩAGNIR, ΩSFGIR) show smooth and steady increase from lower redshift (the Revised Bright Galaxy Sample) to higher redshift (the AKARI NEP deep survey).
Monthly Notices of the Royal Astronomical Society 06/2011; 414(3):1903 - 1913. · 4.90 Impact Factor
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Tomotsugu Goto, Stephane Arnouts,
Matthew Malkan,
Toshinobu Takagi,
Hanae Inami,
Chris Pearson,
Takehiko Wada,
Hideo Matsuhara,
Chisato Yamauchi,
Tsutomu T. Takeuchi,
Takao Nakagawa,
Shinki Oyabu,
Daisuke Ishihara,
David B. Sanders,
Emeric Le Floc'h,
Hyung Mok Lee,
Woong-Seob Jeong,
Stephen Serjeant,
Chris Sedgwick
[show abstract]
[hide abstract]
ABSTRACT: By cross-correlating AKARI infrared (IR) sources with the SDSS galaxies, we
identified 2357 infrared galaxies with a spectroscopic redshift. This is not
just one of the largest samples of local IR galaxies, but AKARI provides
crucial FIR bands (9, 18, 65, 90, 140, and 160um) in accurately measuring
galaxy SED across the peak of the dust emission at ~100um. By fitting modern IR
SED models to the AKARI photometry, we measured the total infrared luminosity
(L_IR) of individual galaxies more accurately. Using this L_IR, we constructed
luminosity functions of infrared galaxies at a median redshift of z=0.031, with
4 times larger sample than previous work. The LF agrees well with that at
z=0.0082 (RBGS), showing smooth and continuous evolution toward higher redshift
LFs measured in the AKARI NEP deep field. The derived local cosmic IR
luminosity density is Omega_IR=3.8x10^8 LsunMpc^-3. We separate galaxies into
AGN, star-forming, and composite by using the [NII]/Ha vs [OIII]/Hb line
ratios. The fraction of AGN shows a continuous increase with increasing L_IR
from 25% to 90% at 9<log L_IR<12.5. The SFR_Ha and L_[OIII] show good
correlations with L_IR for SFG (star-forming galaxies) and AGN, respectively.
The self-absorption corrected Ha/Hb ratio shows a weak increase with L_IR with
a substantial scatter. When we separate IR LFs into contributions from AGN and
SFG, the AGN contribution becomes dominant at L_IR>10^11Lsun, coinciding the
break of the both SFG and AGN IR LFs. At L_IR<10^11Lsun, SFG dominates IR Lfs.
Only 1.1% of Omega_IR is produced by LIRG, and only 0.03% is by ULIRG in the
local Universe. This work also provides the most accurate infrared luminosity
density of the local Universe to date. Compared with high redshift results from
the AKARI NEP deep survey, we observed a strong evolution of Omega_IR^SFG
~(1+z)^4.1+-0.4 and Omega_IR^AGN ~(1+z)^4.1+-0.5 (abridged).
02/2011;
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Tomotsugu Goto, Stephane Arnouts,
Hanae Inami,
Hideo Matsuhara,
Chris Pearson,
Tsutomu T. Takeuchi,
Emeric Le Floc'h,
Toshinobu Takagi,
Takehiko Wada,
Takao Nakagawa,
Shinki Oyabu,
Daisuke Ishihara,
Hyung Mok Lee,
Woong-Seob Jeong,
Chisato Yamauchi,
Stephen Serjeant,
Chris Sedgwick,
Ezequiel Treister
[show abstract]
[hide abstract]
ABSTRACT: Infrared (IR) luminosity is fundamental to understanding the cosmic star formation history and AGN evolution. The AKARI IR space telescope performed all sky survey in 6 IR bands (9, 18, 65, 90, 140, and 160um) with 3-10 times better sensitivity than IRAS, covering the crucial far-IR wavelengths across the peak of the dust emission. Combined with a better spatial resolution, AKARI can much more precisely measure the total infrared luminosity (L_TIR) of individual galaxies, and thus, the total infrared luminosity density in the local Universe. By fitting IR SED models, we have re-measured L_TIR of the IRAS Revised Bright Galaxy Sample. We present mid-IR monochromatic luminosity to L_TIR conversions for Spitzer 8,24um, AKARI 9,18um, IRAS 12um, WISE 12,22um, and ISO 15um filters, with scatter ranging 13-44%. The resulting AKARI IR luminosity function (LF) agrees well with that from the IRAS. We integrate the LF weighted by L_TIR to obtain a cosmic IR luminosity density of Omega_TIR= (8.5^{+1.5}_{-2.3})x 10^7 L Mpc^-3, of which 7+-1% is produced by LIRGs, and only 0.4+-0.1% is from ULIRGs in the local Universe. Once IR contributions from AGN and star-forming galaxies (SFG) are separated, SFG IR LF shows a steep decline at the bright-end. Compared with high-redshift results from the AKARI NEP deep survey, these data show a strong evolution of Omega_TIRSF propto (1+z)^4.0+-0.5, and Omega_TIRAGN propto (1+z)^4.4+-0.4. For Omega_TIRAGN, the ULIRG contribution exceeds that from LIRG already by z~1. A rapid evolution in both Omega_TIRAGN and Omega_TIRSFG suggests the correlation between star formation and black hole accretion rate continues up to higher redshifts. We compare the evolution of Omega_TIRAGN to that of X-ray luminosity density. The Omega_TIRAGN/Omega_X-rayAGN ratio shows a possible increase at z>1, suggesting an increase of obscured AGN at z>1. Comment: Accepted for publication in MNRAS
08/2010;
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[show abstract]
[hide abstract]
ABSTRACT: We present a study of the average properties of luminous infrared galaxies detected directly at 24 μm in the COSMOS field using a median stacking analysis at 70 μm and 160 μm. Over 35,000 sources spanning 0 ≤ z ≤ 3 and 0.06 mJy ≤S 24 ≤ 3.0 mJy are stacked, divided into bins of both photometric redshift and 24 μm flux. We find no correlation of S 70/S 24 flux density ratio with S 24, but find that galaxies with higher S 24 have a lower S 160/S 24 flux density ratio. These observed ratios suggest that 24 μm selected galaxies have warmer spectral energy distributions (SEDs) at higher mid-IR fluxes, and therefore have a possible higher fraction of active galactic nuclei. Comparisons of the average S 70/S 24 and S 160/S 24 colors with various empirical templates and theoretical models show that the galaxies detected at 24 μm are consistent with "normal" star-forming galaxies and warm mid-IR galaxies such as Mrk 231, but inconsistent with heavily obscured galaxies such as Arp 220. We perform a χ2 analysis to determine best-fit galactic model SEDs and total IR luminosities for each of our bins. We compare our results to previous methods of estimating L IR and find that previous methods show considerable agreement over the full redshift range, except for the brightest S 24 sources, where they overpredict the bolometric IR luminosity at high redshift, most likely due to their warmer dust SED. We present a table that can be used as a more accurate and robust method for estimating bolometric infrared luminosity from 24 μm flux densities.
The Astrophysical Journal 06/2010; 717(1):175. · 6.02 Impact Factor
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[show abstract]
[hide abstract]
ABSTRACT: We present a study of the average properties of luminous infrared galaxies detected directly at 24 $\mu$m in the COSMOS field using a median stacking analysis at 70$\mu$m and 160 $\mu$m. Over 35000 sources spanning 0<z<3 and 0.06 mJy<S_{24}<3.0 mJy are stacked, divided into bins of both photometric redshift and 24 $\mu$m flux. We find no correlation of $S_{70}/S_{24}$ flux density ratio with $S_{24}$, but find that galaxies with higher $S_{24}$ have a lower $S_{160}/S_{24}$ flux density ratio. These observed ratios suggest that 24 $\mu$m selected galaxies have warmer SEDs at higher mid-IR fluxes, and therefore have a possible higher fraction of AGN. Comparisons of the average $S_{70}/S_{24}$ and $S_{160}/S_{24}$ colors with various empirical templates and theoretical models show that the galaxies detected at 24 $\mu$m are consistent with "normal" star-forming galaxies and warm mid-IR galaxies such as Mrk 231, but inconsistent with heavily obscured galaxies such as Arp 220. We perform a $\chi^{2}$ analysis to determine best fit galactic model SEDs and total IR luminosities for each of our bins. We compare our results to previous methods of estimating $L_{\rm{IR}}$ and find that previous methods show considerable agreement over the full redshift range, except for the brightest $S_{24}$ sources, where previous methods overpredict the bolometric IR luminosity at high redshift, most likely due to their warmer dust SED. We present a table that can be used as a more accurate and robust method for estimating bolometric infrared luminosity from 24 $\mu$m flux densities. Comment: 21 pages, 6 figures, accepted for publication in the Astrophysical Journal
05/2010;
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[show abstract]
[hide abstract]
ABSTRACT: We present a source catalog from deep 26 ks GALEX observations of the Coma cluster in the far-UV (FUV; 1530 A) and near-UV (NUV; 2310 A) wavebands. The observed field is centered 0.9 deg (1.6 Mpc) south-west of the Coma core, and has full optical photometric coverage with SDSS. The catalog consists of 9700 galaxies with GALEX and SDSS photometry, including 242 spectroscopically-confirmed Coma member galaxies that range from giant spirals and elliptical galaxies to dwarf irregular and early-type galaxies. The full multi-wavelength catalog (cluster plus background galaxies) is ~80% complete to NUV=23 and FUV=23.5, and has a limiting depth at NUV=24.5 and FUV=25.0 which corresponds to a star formation rate of ~0.001 Msun/yr at the distance of Coma. Our deep GALEX observations required a two-fold approach to generating a source catalog: we used a Bayesian deblending algorithm to measure faint and compact sources (using SDSS coordinates as a position prior), and relied on the GALEX pipeline catalog for bright/extended objects. We performed simulations to assess the influence that systematic effects (e.g. object blends, source confusion, Eddington Bias) have on source detection and photometry when using both methods. The Bayesian deblending method roughly doubles the number of source detections and provides reliable photometry to a few magnitudes deeper than the GALEX pipeline catalog. This method is also free from source confusion over the UV magnitude range studied here; conversely, we estimate that the GALEX pipeline catalogs are confusion limited at magnitudes fainter than NUV~23 and FUV~24. We have measured the total UV galaxy counts using our catalog and report a ~50% excess of counts across FUV=22-23.5 and NUV=21.5-23 relative to previous GALEX measurements, which is not attributed to cluster member galaxies. Our galaxy counts are a better match to deeper UV counts measured with HST. Comment: 27 pages, 13 figures, 4 tables, accepted for publication in ApJS
04/2010;
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Emeric Le Floc'h,
Hervé Aussel,
Olivier Ilbert,
Laurie Riguccini,
David T. Frayer,
Mara Salvato, Stephane Arnouts,
Jason Surace,
Chiara Feruglio,
Giulia Rodighiero,
Peter Capak,
Jeyhan Kartaltepe,
Sebastien Heinis,
Kartik Sheth,
Lin Yan,
Henry Joy McCracken,
David Thompson,
David Sanders,
Nick Scoville,
and Anton Koekemoer
[show abstract]
[hide abstract]
ABSTRACT: We present the first results obtained from the identification of ~30,000 sources in the Spitzer/24 μm observations of the COSMOS field at S 24 μm 80 μJy. Using accurate photometric redshifts (σ z ~ 0.12 at z ~ 2 for 24 μm sources with i + 25 mag AB) and simple extrapolations of the number counts at faint fluxes, we resolve with unprecedented detail the buildup of the mid-infrared background across cosmic ages. We find that ~50% and ~80% of the 24 μm background intensity originate from galaxies at z 1 and z 2, respectively, supporting the scenario where highly obscured sources at very high redshifts (z 2) contribute only marginally to the cosmic infrared background. Assuming flux-limited selections at optical wavelengths, we also find that the fraction of i +-band sources with 24 μm detection strongly increases up to z ~ 2 as a consequence of the rapid evolution that star-forming galaxies have undergone with look-back time. Nonetheless, this rising trend shows a clear break at z ~ 1.3, probably due to k-correction effects implied by the complexity of spectral energy distributions in the mid-infrared. Finally, we compare our results with the predictions from different models of galaxy formation. We note that semianalytical formalisms currently fail to reproduce the redshift distributions observed at 24 μm. Furthermore, the simulated galaxies at S 24 μm > 80 μJy exhibit R–K colors much bluer than observed and the predicted K-band fluxes are systematically underestimated at z 0.5. Unless these discrepancies mainly result from an incorrect treatment of extinction in the models they may reflect an underestimate of the predicted density of high-redshift massive sources with strong ongoing star formation, which would point to more fundamental processes and/or parameters (e.g., initial mass function, critical density to form stars, feedback,...) that are still not fully controlled in the simulations. The most recent backward evolution scenarios reproduce reasonably well the flux/redshift distribution of 24 μm sources up to z ~ 3, although none of them is able to exactly match our results at all redshifts.
The Astrophysical Journal 08/2009; 703(1):222. · 6.02 Impact Factor
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Patrick Morrissey,
Tim Conrow,
Tom A. Barlow,
Todd Small,
Mark Seibert,
Ted K. Wyder,
Tamás Budavári, Stephane Arnouts,
Peter G. Friedman,
Karl Forster, [......],
Luciana Bianchi,
José Donas,
Timothy M. Heckman,
Young-Wook Lee,
Barry F. Madore,
Bruno Milliard,
R. Michael Rich,
Alex S. Szalay,
Barry Y. Welsh,
and Sukyoung K. Yi
[show abstract]
[hide abstract]
ABSTRACT: We describe the calibration status and data products pertaining to the GR2 and GR3 data releases of the Galaxy Evolution Explorer (GALEX). These releases have identical pipeline calibrations that are significantly improved over the GR1 data release. GALEX continues to survey the sky in the far-ultraviolet (FUV, ~154 nm) and near-ultraviolet (NUV, ~232 nm) bands, providing simultaneous imaging with a pair of photon-counting, microchannel plate, delay line readout detectors. These 1.25° field of view detectors are well suited to ultraviolet observations because of their excellent red rejection and negligible background. A dithered mode of observing and photon list output pose complex requirements on the data processing pipeline, entangling detector calibrations, and aspect reconstruction algorithms. Recent improvements have achieved photometric repeatability of 0.05 and 0.03 mAB in the FUV and NUV, respectively. We have detected a long-term drift of order 1% FUV and 6% NUV over the mission. Astrometric precision is of order 0.5'' rms in both bands. In this paper we provide the GALEX user with a broad overview of the calibration issues likely to be confronted in the current release. Improvements are likely as the GALEX mission continues into an extended phase with a healthy instrument, no consumables, and increased opportunities for guest investigations.
The Astrophysical Journal Supplement Series 12/2008; 173(2):682. · 13.46 Impact Factor
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C. Kevin Xu,
Jose Donas, Stephane Arnouts,
Ted K. Wyder,
Mark Seibert,
Jorge Iglesias-Páramo,
Jeremy Blaizot,
Todd Small,
Bruno Milliard,
David Schiminovich, [......],
Patrick N. Jelinsky,
Young-Wook Lee,
Barry F. Madore,
Roger F. Malina,
Patrick Morrissey,
Susan G. Neff,
R. Michael Rich,
Oswald H. W. Siegmund,
Alex S. Szalay,
and Barry Y. Welsh
[show abstract]
[hide abstract]
ABSTRACT: Number counts of galaxies in two Galaxy Evolution Explorer (GALEX) bands [far-UV (FUV: 1530 Å) and near-UV (NUV: 2310 Å); both in AB magnitudes] are reported. They provide for the first time in the literature homogeneously calibrated number counts of UV galaxies continuously covering a very wide range in UV magnitude (14-23.8). Both the FUV and NUV counts are inconsistent with a nonevolution model, whereas they are in good agreement with evolution models (essentially luminosity evolution) derived from the high-z UV luminosity functions of Arnouts et al. We find that the contribution from GALEX-detected galaxies to the UV background is 0.68 ± 0.10 nW m-2 sr-1 at 1530 Å and 0.99 ± 0.15 nW m-2 sr-1 at 2310 Å. These are 66% ± 9% and 44% ± 6% of the total contributions of galaxies to the UV background at 1530 Å (1.03 ± 0.15 nW m-2 sr-1) and at 2310 Å (2.25 ± 0.32 nW m-2 sr-1), respectively, as estimated using the evolution models. Galaxy counts and star counts in seven regions, each containing a few square degrees of GALEX coverage in an area of ~4-13 deg2, are compared with each other to study the region-by-region variance. This shows that for the galaxy counts, the cosmic variance is comparable to the net error due to other uncertainties. The star counts increase with decreasing absolute Galactic latitude |b|.
The Astrophysical Journal 12/2008; 619(1):L11. · 6.02 Impact Factor
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Michael Rowan-Robinson,
Tom Babbedge,
Seb Oliver,
Markos Trichas,
Stefano Berta,
Carol Lonsdale,
Gene Smith,
David Shupe,
Jason Surace, Stephane Arnouts,
Olivier LeFevre,
Alejandro Afonso-Luis,
Ismael Perez-Fournon,
Evanthia Hatziminaoglou,
Maria Polletta,
Duncan Farrah,
Mattia Vaccari
[show abstract]
[hide abstract]
ABSTRACT: We present the SWIRE Photometric Redshift Catalogue, 1025119 redshifts of unprecedented reliability and accuracy. Our method is based on fixed galaxy and QSO templates applied to data at 0.36-4.5 mu, and on a set of 4 infrared emission templates fitted to infrared excess data at 3.6-170 mu. The code involves two passes through the data, to try to optimize recognition of AGN dust tori. A few carefully justified priors are used and are the key to supression of outliers. Extinction, A_V, is allowed as a free parameter. We use a set of 5982 spectroscopic redshifts, taken from the literature and from our own spectroscopic surveys, to analyze the performance of our method as a function of the number of photometric bands used in the solution and the reduced chi^2. For 7 photometric bands the rms value of (z_{phot}-z_{spec})/(1+z_{spec}) is 3.5%, and the percentage of catastrophic outliers is ~1%. We discuss the redshift distributions at 3.6 and 24 mu. In individual fields, structure in the redshift distribution corresponds to clusters which can be seen in the spectroscopic redshift distribution. 10% of sources in the SWIRE photometric redshift catalogue have z >2, and 4% have z>3, so this catalogue is a huge resource for high redshift galaxies. A key parameter for understanding the evolutionary status of infrared galaxies is L_{ir}/L_{opt}, which can be interpreted as the specific star-formation rate for starbursts. For dust tori around Type 1 AGN, L_{tor}/L_{opt} is a measure of the torus covering factor and we deduce a mean covering factor of 40%. Comment: 22 pages, 23 figures. Accepted for publication in MNRAS. Revised 28/2/08. Version with figures at full resolution at http://astro.ic.ac.uk/~mrr/swirephotzcat/swirephotz5.pdf.gz
02/2008;
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[show abstract]
[hide abstract]
ABSTRACT: The aim of this paper is to investigate ways to optimize the accuracy of photometric redshifts for a SNAP like mission. We focus on how the accuracy of the photometric redshifts depends on the magnitude limit and signal-to-noise ratio, wave-length coverage, number of filters and their shapes and observed galaxy type. We use simulated galaxy catalogs constructed to reproduce observed galaxy luminosity functions from GOODS, and derive photometric redshifts using a template fitting method. By using a catalog that resembles real data, we can estimate the expected number density of galaxies for which photometric redshifts can be derived. We find that the accuracy of photometric redshifts is strongly dependent on the signal-to-noise (S/N) (i.e., S/N>10 is needed for accurate photometric redshifts). The accuracy of the photometric redshifts is also dependent on galaxy type, with smaller scatter for earlier type galaxies. Comparing results using different filter sets, we find that including the U-band is important for decreasing the fraction of outliers, i.e., ``catastrophic failures''. Using broad overlapping filters with resolution ~4gives better photometric redshifts compared to narrower filters (resolution >~5) with the same integration time. We find that filters with square response curves result in a slightly higher scatter, mainly due to a higher fraction of outliers at faint magnitudes. We also compare a 9-filter set to a 17-filter set, where we assume that the available exposure time per filter in the latter set is half that of the first set. We find that the 9-filter set gives more accurate redshifts for a larger number of objects and reaches higher redshift, while the 17-filter set is gives better results at bright magnitudes. Comment: 30 pages, 10 figures. Submitted to AJ
The Astronomical Journal 10/2007; · 4.03 Impact Factor
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Bruno Milliard,
Sebastien Heinis,
Jeremy Blaizot, Stephane Arnouts,
David Schiminovich,
Tamas Budavari,
Jose Donas,
Marie Treyer,
Michel Laget,
Maurice Viton, [......],
Mark Seibert,
Todd Small,
Luciana Bianchi,
Timothy M. Heckman,
Young-Wook Lee,
Barry F. Madore,
R. Michael Rich,
Barry Y. Welsh,
Sukyoung K. Yi,
C. K. Xu
[show abstract]
[hide abstract]
ABSTRACT: We present the first measurements of the angular correlation function of galaxies selected in the far (1530 A) and near (2310 A) Ultraviolet from the GALEX survey fields overlapping SDSS DR5 in low galactic extinction regions. The area used covers 120 sqdeg (GALEX - MIS) down to magnitude AB = 22, yielding a total of 100,000 galaxies. The mean correlation length is ~ 3.7 \pm 0.6 Mpc and no significant trend is seen for this value as a function of the limiting apparent magnitude or between the GALEX bands. This estimate is close to that found from samples of blue galaxies in the local universe selected in the visible, and similar to that derived at z ~ 3 for LBGs with similar rest frame selection criteria. This result supports models that predict anti-biasing of star forming galaxies at low redshift, and brings an additional clue to the downsizing of star formation at z<1. Comment: Accepted for publication in GALEX Special ApJs, December 2007
10/2007;
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Patrick Morrissey,
Tim Conrow,
Tom A. Barlow,
Todd Small,
Mark Seibert,
Ted K. Wyder,
Tamas Budavari, Stephane Arnouts,
Peter G. Friedman,
Karl Forster, [......],
Luciana Bianchi,
Jose Donas,
Timothy M. Heckman,
Young-Wook Lee,
Barry F. Madore,
Bruno Milliard,
R. Michael Rich,
Alex S. Szalay,
Barry Y. Welsh,
Sukyoung K. Yi
[show abstract]
[hide abstract]
ABSTRACT: We describe the calibration status and data products pertaining to the GR2 and GR3 data releases of the Galaxy Evolution Explorer (GALEX). These releases have identical pipeline calibrations that are significantly improved over the GR1 data release. GALEX continues to survey the sky in the Far Ultraviolet (FUV, ~154 nm) and Near Ultraviolet (NUV, ~232 nm) bands, providing simultaneous imaging with a pair of photon counting, microchannel plate, delay line readout detectors. These 1.25 degree field-of-view detectors are well-suited to ultraviolet observations because of their excellent red rejection and negligible background. A dithered mode of observing and photon list output pose complex requirements on the data processing pipeline, entangling detector calibrations and aspect reconstruction algorithms. Recent improvements have achieved photometric repeatability of 0.05 and 0.03 mAB in the FUV and NUV, respectively. We have detected a long term drift of order 1% FUV and 6% NUV over the mission. Astrometric precision is of order 0.5" RMS in both bands. In this paper we provide the GALEX user with a broad overview of the calibration issues likely to be confronted in the current release. Improvements are likely as the GALEX mission continues into an extended phase with a healthy instrument, no consumables, and increased opportunities for guest investigations.
07/2007;
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Sebastien Heinis,
Bruno Milliard, Stephane Arnouts,
Jeremy Blaizot,
David Schiminovich,
Tamas Budavari,
Olivier Ilbert,
Marie Treyer,
Ted K. Wyder,
Henry J. McCracken, [......],
Todd Small,
Luciana Bianchi,
Timothy M. Heckman,
Young-Wook Lee,
Barry F. Madore,
R. Michael Rich,
Alex S. Szalay,
Barry Y. Welsh,
Sukyoung K. Yi,
C. K. Xu
[show abstract]
[hide abstract]
ABSTRACT: We analyze the clustering properties of ultraviolet selected galaxies by using GALEX-SDSS data at z<0.6 and CFHTLS deep u' imaging at z=1. These datasets provide a unique basis at z< 1 which can be directly compared with high redshift samples built with similar selection criteria. We discuss the dependence of the correlation function parameters (r0, delta) on the ultraviolet luminosity as well as the linear bias evolution. We find that the bias parameter shows a gradual decline from high (b > 2) to low redshift (b ~ 0.79^{+0.1}_{-0.08}). When accounting for the fraction of the star formation activity enclosed in the different samples, our results suggest that the bulk of star formation migrated from high mass dark matter halos at z>2 (10^12 < M_min < 10^13 M_sun, located in high density regions), to less massive halos at low redshift (M_min < 10^12 M_sun, located in low density regions). This result extends the ``downsizing'' picture (shift of the star formation activity from high stellar mass systems at high z to low stellar mass at low z) to the dark matter distribution. Comment: Accepted for Publication in the Special GALEX Ap. J. Supplement, December 2007 Version with full resolution fig1 available at http://taltos.pha.jhu.edu/~sebastien/papers/Galex_p2.ps.gz
06/2007;
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C. Kevin Xu,
Jose Donas, Stephane Arnouts,
Ted K. Wyder,
Mark Seibert,
Jorge Iglesias-Paramo,
Jeremy Blaizot,
Todd Small,
Bruno Milliard,
David Schiminovich, [......],
Karl Forster,
Peter G. Friedman,
Timothy M. Heckman,
Patrick N. Jelinsky,
Young-Wook Lee,
Barry F. Madore,
Roger F. Malina,
Patrick Morrissey,
Susan G. Neff,
R. Michael Rich
[show abstract]
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ABSTRACT: Number Counts of galaxies in two GALEX bands (FUV: 1530A and NUV: 2310A, both in AB magnitudes) are reported. They provide for the first time in the literature homogeneously calibrated number counts of UV galaxies covering continuously a very wide range of UV magnitude (14 -- 23.8). Both the FUV and NUV counts are inconsistent with a non-evolution model, while they are in good agreement with evolution models (essentially luminosity evolution) derived from the high-z UV luminosity functions of Arnouts et al. (2004). It is found that the contribution from galaxies detected by GALEX to the UV background is 0.68+-0.10 nW m-2 sr-1 at 1530A and 0.99+-0.15 nW m-2 sr-1 at 2310A. These are 66+-9% and 44+-6% of the total contributions of galaxies to the the UV background at 1530A, respectively, as estimated using the evolution models. ... Comment: This paper will be published as part of the Galaxy Evolution Explorer (GALEX) Astrophysical Journal Letters Special Issue. Links to the full set of papers will be available at http:/www.galex.caltech.edu/PUBLICATIONS/ after November 22, 2004
11/2004;
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Michael Rowan-Robinson,
Tom Babbedge,
Seb Oliver,
Markos Trichas,
Stefano Berta,
Carol Lonsdale,
Gene Smith,
David Shupe,
Jason Surace, Stephane Arnouts,
Olivier Ilbert,
Olivier Le Févre,
Alejandro Afonso-Luis,
Ismael Perez-Fournon,
Evanthia Hatziminaoglou,
Mari Polletta,
Duncan Farrah,
Mattia Vaccari
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ABSTRACT: We present the SWIRE Photometric Redshift Catalogue 1 025 119 redshifts of unprecedented reliability and of accuracy comparable with or better than previous work. Our methodology is based on fixed galaxy and quasi-stellar object templates applied to data at 0.36–4.5 μm, and on a set of four infrared emission templates fitted to infrared excess data at 3.6–170 μm. The galaxy templates are initially empirical, but are given greater physical validity by fitting star formation histories to them, which also allows us to estimate stellar masses. The code involves two passes through the data, to try to optimize recognition of active galactic nucleus (AGN) dust tori. A few carefully justified priors are used and are the key to supression of outliers. Extinction, A_V , is allowed as a free parameter. The full reduced χ^2_ν (z) distribution is given for each source, so the full error distribution can be used, and aliases investigated.
We use a set of 5982 spectroscopic redshifts, taken from the literature and from our own spectroscopic surveys, to analyse the performance of our method as a function of the number of photometric bands used in the solution and the reduced χ^2_ν . For seven photometric bands (5 optical + 3.6, 4.5 μm), the rms value of (z_(phot)−z_(spec)/(1 +z_(spec) is 3.5 per cent, and the percentage of catastrophic outliers [defined as >15 per cent error in (1 +z)], is ∼1 per cent. These rms values are comparable with the best achieved in other studies, and the outlier fraction is significantly better. The inclusion of the 3.6- and 4.5-μm IRAC bands is crucial in supression of outliers.
We discuss the redshift distributions at 3.6 and 24 μm. In individual fields, structure in the redshift distribution corresponds to clusters which can be seen in the spectroscopic redshift distribution, so the photometric redshifts are a powerful tool for large-scale structure studies. 10 per cent of sources in the SWIRE photometric redshift catalogue have z > 2, and 4 per cent have z > 3, so this catalogue is a huge resource for high-redshift galaxies.
A key parameter for understanding the evolutionary status of infrared galaxies is L_(ir)/L_(opt) . For cirrus galaxies this is a measure of the mean extinction in the interstellar medium of the galaxy. There is a population of ultraluminous galaxies with cool dust and we have shown SEDs for some of the reliable examples. For starbursts, we estimate the specific star formation rate, φ_*/M_* . Although the very highest values of this ratio tend to be associated with Arp220 starbursts, by no means all ultraluminous galaxies are. We discuss an interesting population of galaxies with elliptical-like spectral energy distributions in the optical and luminous starbursts in the infrared.
For dust tori around type 1 AGN, L_(tor)/L_(opt) is a measure of the torus covering factor and we deduce a mean covering factor of 40 per cent.
Our infrared templates also allow us to estimate dust masses for all galaxies with an infrared excess.
