The Experts below are selected from a list of 25143 Experts worldwide ranked by ideXlab platform
R J Bouwens - One of the best experts on this subject based on the ideXlab platform.
-
ultradeep infrared array camera observations of sub l z 7 and z 8 galaxies in the hubble ultra deep field the contribution of low luminosity galaxies to the stellar mass density and reionization
The Astrophysical Journal, 2010Co-Authors: Ivo Labbe, R J Bouwens, G D Illingworth, Valentino Gonzalez, Pascal Oesch, P G Van Dokkum, C M Carollo, Marijn Franx, M StiavelliAbstract:We study the Spitzer Infrared Array Camera (IRAC) mid-infrared (rest-frame optical) fluxes of 14 newly WFC3/IR-detected z ~ 7 z 850-dropout galaxies and 5z ~ 8 Y 105-dropout galaxies. The WFC3/IR depth and spatial resolution allow accurate removal of contaminating foreground light, enabling reliable flux measurements at 3.6 μm and 4.5 μm. None of the galaxies are detected to [3.6] 26.9 (AB, 2σ), but a stacking analysis reveals a robust detection for the z 850-Dropouts and an upper limit for the Y 105-Dropouts. We construct average broadband spectral energy distributions using the stacked Advanced Camera for Surveys (ACS), WFC3, and IRAC fluxes and fit stellar population synthesis models to derive mean redshifts, stellar masses, and ages. For the z 850-Dropouts, we find z = 6.9+0.1 –0.1, (U – V)rest 0.4, reddening AV = 0, stellar mass M* = 1.2+0.3 –0.6 × 109 M ☉ (Salpeter initial mass function). The best-fit ages ~300 Myr, M/LV 0.2, and SSFR ~1.7 Gyr–1 are similar to values reported for luminous z ~ 7 galaxies, indicating the galaxies are smaller but not much younger. The sub-L* galaxies observed here contribute significantly to the stellar mass density and under favorable conditions may have provided enough photons for sustained reionization at 7 < z < 11. In contrast, the z = 8.3+0.1 –0.2 Y 105-Dropouts have stellar masses that are uncertain by 1.5 dex due to the near-complete reliance on far-UV data. Adopting the 2σ upper limit on the M/L(z = 8), the stellar mass density to M UV,AB < –18 declines from ρ*(z = 7) = 3.7+1.4 –1.8 × 106 M ☉ Mpc–3 to ρ*(z = 8) < 8 × 105 M ☉ Mpc–3, following (1 + z)–6 over 3 < z < 8. Lower masses at z = 8 would signify more dramatic evolution, which can be established with deeper IRAC observations, long before the arrival of the James Webb Space Telescope.
-
ultradeep infrared array camera observations of sub l z 7 and z 8 galaxies in the hubble ultra deep field the contribution of low luminosity galaxies to the stellar mass density and reionization
arXiv: Cosmology and Nongalactic Astrophysics, 2009Co-Authors: Ivo Labbe, R J Bouwens, G D Illingworth, Valentino Gonzalez, Pascal Oesch, P G Van Dokkum, C M Carollo, Marijn Franx, M StiavelliAbstract:We study the Spitzer Infrared Array Camera (IRAC) mid-infrared (rest-frame optical) fluxes of 14 newly WFC3/IR-detected z=7 z_{850}-dropout galaxies and 5 z=8 Y_{105}-dropout galaxies. The WFC3/IR depth and spatial resolution allow accurate removal of contaminating foreground light, enabling reliable flux measurements at 3.6 micron and 4.5 micron. None of the galaxies are detected to [3.6]=26.9 (AB, 2 sigma), but a stacking analysis reveals a robust detection for the z_{850}-Dropouts and an upper limit for the Y_{105}-Dropouts. We construct average broadband SEDs using the stacked ACS, WFC3, and IRAC fluxes and fit stellar population synthesis models to derive mean redshifts, stellar masses, and ages. For the z_{850}-Dropouts, we find z=6.9^{+0.1}_{-0.1}, (U-V)_{rest}=0.4, reddening A_V=0, stellar mass M*=1.2^{+0.3}_{-0.6} x 10^9 M_sun (Salpeter IMF). The best-fit ages ~300Myr, M/L_V=0.2, and SSFR=1.7Gyr^{-1} are similar to values reported for luminous z=7 galaxies, indicating the galaxies are smaller but not younger. The sub-L* galaxies observed here contribute significantly to the stellar mass density and under favorable conditions may have provided enough photons for sustained reionization at 7
-
galaxy size evolution at high redshift and surface brightness selection effects constraints from the hubble ultra deep field
The Astrophysical Journal, 2004Co-Authors: R J Bouwens, G D Illingworth, John P Blakeslee, Tom Broadhurst, M FranxAbstract:We use the exceptional depth of the Ultra Deep Field (UDF) and UDF-parallel Advanced Camera for Surveys fields to study the sizes of high-redshift (z ~ 2-6) galaxies and address long-standing questions about possible biases in the cosmic star formation rate due to surface brightness dimming. Contrasting B-, V-, and i-dropout samples culled from the deeper data with those obtained from the shallower Great Observatories Origins Deep Survey fields, we demonstrate that the shallower data are essentially complete at bright magnitudes to z 5.5 and that the principal effect of depth is to add objects at the magnitude limit. This indicates that high-redshift galaxies are compact in size (~01-03) and that large (04, 3 kpc) low surface brightness galaxies are rare. A simple comparison of the half-light radii of the Hubble Deep Field-North + Hubble Deep Field-South U-Dropouts with B-, V-, and i-Dropouts from the UDF shows that the sizes follow a (1 + z)-1.05±0.21 scaling toward high redshift. A more rigorous measurement compares different scalings of our U-dropout sample with the mean profiles for a set of intermediate-magnitude (26.0 < z850, AB < 27.5) i-Dropouts from the UDF. The best fit is found with a (1 + z) size scaling (for fixed luminosity). This result is then verified by repeating this experiment with different size measures, low-redshift samples, and magnitude ranges. Very similar scalings are found for all comparisons. A robust measurement of size evolution is thereby demonstrated for galaxies from z ~ 6 to 2.5 using data from the UDF.
M Stiavelli - One of the best experts on this subject based on the ideXlab platform.
-
ultradeep infrared array camera observations of sub l z 7 and z 8 galaxies in the hubble ultra deep field the contribution of low luminosity galaxies to the stellar mass density and reionization
The Astrophysical Journal, 2010Co-Authors: Ivo Labbe, R J Bouwens, G D Illingworth, Valentino Gonzalez, Pascal Oesch, P G Van Dokkum, C M Carollo, Marijn Franx, M StiavelliAbstract:We study the Spitzer Infrared Array Camera (IRAC) mid-infrared (rest-frame optical) fluxes of 14 newly WFC3/IR-detected z ~ 7 z 850-dropout galaxies and 5z ~ 8 Y 105-dropout galaxies. The WFC3/IR depth and spatial resolution allow accurate removal of contaminating foreground light, enabling reliable flux measurements at 3.6 μm and 4.5 μm. None of the galaxies are detected to [3.6] 26.9 (AB, 2σ), but a stacking analysis reveals a robust detection for the z 850-Dropouts and an upper limit for the Y 105-Dropouts. We construct average broadband spectral energy distributions using the stacked Advanced Camera for Surveys (ACS), WFC3, and IRAC fluxes and fit stellar population synthesis models to derive mean redshifts, stellar masses, and ages. For the z 850-Dropouts, we find z = 6.9+0.1 –0.1, (U – V)rest 0.4, reddening AV = 0, stellar mass M* = 1.2+0.3 –0.6 × 109 M ☉ (Salpeter initial mass function). The best-fit ages ~300 Myr, M/LV 0.2, and SSFR ~1.7 Gyr–1 are similar to values reported for luminous z ~ 7 galaxies, indicating the galaxies are smaller but not much younger. The sub-L* galaxies observed here contribute significantly to the stellar mass density and under favorable conditions may have provided enough photons for sustained reionization at 7 < z < 11. In contrast, the z = 8.3+0.1 –0.2 Y 105-Dropouts have stellar masses that are uncertain by 1.5 dex due to the near-complete reliance on far-UV data. Adopting the 2σ upper limit on the M/L(z = 8), the stellar mass density to M UV,AB < –18 declines from ρ*(z = 7) = 3.7+1.4 –1.8 × 106 M ☉ Mpc–3 to ρ*(z = 8) < 8 × 105 M ☉ Mpc–3, following (1 + z)–6 over 3 < z < 8. Lower masses at z = 8 would signify more dramatic evolution, which can be established with deeper IRAC observations, long before the arrival of the James Webb Space Telescope.
-
ultradeep infrared array camera observations of sub l z 7 and z 8 galaxies in the hubble ultra deep field the contribution of low luminosity galaxies to the stellar mass density and reionization
arXiv: Cosmology and Nongalactic Astrophysics, 2009Co-Authors: Ivo Labbe, R J Bouwens, G D Illingworth, Valentino Gonzalez, Pascal Oesch, P G Van Dokkum, C M Carollo, Marijn Franx, M StiavelliAbstract:We study the Spitzer Infrared Array Camera (IRAC) mid-infrared (rest-frame optical) fluxes of 14 newly WFC3/IR-detected z=7 z_{850}-dropout galaxies and 5 z=8 Y_{105}-dropout galaxies. The WFC3/IR depth and spatial resolution allow accurate removal of contaminating foreground light, enabling reliable flux measurements at 3.6 micron and 4.5 micron. None of the galaxies are detected to [3.6]=26.9 (AB, 2 sigma), but a stacking analysis reveals a robust detection for the z_{850}-Dropouts and an upper limit for the Y_{105}-Dropouts. We construct average broadband SEDs using the stacked ACS, WFC3, and IRAC fluxes and fit stellar population synthesis models to derive mean redshifts, stellar masses, and ages. For the z_{850}-Dropouts, we find z=6.9^{+0.1}_{-0.1}, (U-V)_{rest}=0.4, reddening A_V=0, stellar mass M*=1.2^{+0.3}_{-0.6} x 10^9 M_sun (Salpeter IMF). The best-fit ages ~300Myr, M/L_V=0.2, and SSFR=1.7Gyr^{-1} are similar to values reported for luminous z=7 galaxies, indicating the galaxies are smaller but not younger. The sub-L* galaxies observed here contribute significantly to the stellar mass density and under favorable conditions may have provided enough photons for sustained reionization at 7
G D Illingworth - One of the best experts on this subject based on the ideXlab platform.
-
ultradeep infrared array camera observations of sub l z 7 and z 8 galaxies in the hubble ultra deep field the contribution of low luminosity galaxies to the stellar mass density and reionization
The Astrophysical Journal, 2010Co-Authors: Ivo Labbe, R J Bouwens, G D Illingworth, Valentino Gonzalez, Pascal Oesch, P G Van Dokkum, C M Carollo, Marijn Franx, M StiavelliAbstract:We study the Spitzer Infrared Array Camera (IRAC) mid-infrared (rest-frame optical) fluxes of 14 newly WFC3/IR-detected z ~ 7 z 850-dropout galaxies and 5z ~ 8 Y 105-dropout galaxies. The WFC3/IR depth and spatial resolution allow accurate removal of contaminating foreground light, enabling reliable flux measurements at 3.6 μm and 4.5 μm. None of the galaxies are detected to [3.6] 26.9 (AB, 2σ), but a stacking analysis reveals a robust detection for the z 850-Dropouts and an upper limit for the Y 105-Dropouts. We construct average broadband spectral energy distributions using the stacked Advanced Camera for Surveys (ACS), WFC3, and IRAC fluxes and fit stellar population synthesis models to derive mean redshifts, stellar masses, and ages. For the z 850-Dropouts, we find z = 6.9+0.1 –0.1, (U – V)rest 0.4, reddening AV = 0, stellar mass M* = 1.2+0.3 –0.6 × 109 M ☉ (Salpeter initial mass function). The best-fit ages ~300 Myr, M/LV 0.2, and SSFR ~1.7 Gyr–1 are similar to values reported for luminous z ~ 7 galaxies, indicating the galaxies are smaller but not much younger. The sub-L* galaxies observed here contribute significantly to the stellar mass density and under favorable conditions may have provided enough photons for sustained reionization at 7 < z < 11. In contrast, the z = 8.3+0.1 –0.2 Y 105-Dropouts have stellar masses that are uncertain by 1.5 dex due to the near-complete reliance on far-UV data. Adopting the 2σ upper limit on the M/L(z = 8), the stellar mass density to M UV,AB < –18 declines from ρ*(z = 7) = 3.7+1.4 –1.8 × 106 M ☉ Mpc–3 to ρ*(z = 8) < 8 × 105 M ☉ Mpc–3, following (1 + z)–6 over 3 < z < 8. Lower masses at z = 8 would signify more dramatic evolution, which can be established with deeper IRAC observations, long before the arrival of the James Webb Space Telescope.
-
ultradeep infrared array camera observations of sub l z 7 and z 8 galaxies in the hubble ultra deep field the contribution of low luminosity galaxies to the stellar mass density and reionization
arXiv: Cosmology and Nongalactic Astrophysics, 2009Co-Authors: Ivo Labbe, R J Bouwens, G D Illingworth, Valentino Gonzalez, Pascal Oesch, P G Van Dokkum, C M Carollo, Marijn Franx, M StiavelliAbstract:We study the Spitzer Infrared Array Camera (IRAC) mid-infrared (rest-frame optical) fluxes of 14 newly WFC3/IR-detected z=7 z_{850}-dropout galaxies and 5 z=8 Y_{105}-dropout galaxies. The WFC3/IR depth and spatial resolution allow accurate removal of contaminating foreground light, enabling reliable flux measurements at 3.6 micron and 4.5 micron. None of the galaxies are detected to [3.6]=26.9 (AB, 2 sigma), but a stacking analysis reveals a robust detection for the z_{850}-Dropouts and an upper limit for the Y_{105}-Dropouts. We construct average broadband SEDs using the stacked ACS, WFC3, and IRAC fluxes and fit stellar population synthesis models to derive mean redshifts, stellar masses, and ages. For the z_{850}-Dropouts, we find z=6.9^{+0.1}_{-0.1}, (U-V)_{rest}=0.4, reddening A_V=0, stellar mass M*=1.2^{+0.3}_{-0.6} x 10^9 M_sun (Salpeter IMF). The best-fit ages ~300Myr, M/L_V=0.2, and SSFR=1.7Gyr^{-1} are similar to values reported for luminous z=7 galaxies, indicating the galaxies are smaller but not younger. The sub-L* galaxies observed here contribute significantly to the stellar mass density and under favorable conditions may have provided enough photons for sustained reionization at 7
-
galaxy size evolution at high redshift and surface brightness selection effects constraints from the hubble ultra deep field
The Astrophysical Journal, 2004Co-Authors: R J Bouwens, G D Illingworth, John P Blakeslee, Tom Broadhurst, M FranxAbstract:We use the exceptional depth of the Ultra Deep Field (UDF) and UDF-parallel Advanced Camera for Surveys fields to study the sizes of high-redshift (z ~ 2-6) galaxies and address long-standing questions about possible biases in the cosmic star formation rate due to surface brightness dimming. Contrasting B-, V-, and i-dropout samples culled from the deeper data with those obtained from the shallower Great Observatories Origins Deep Survey fields, we demonstrate that the shallower data are essentially complete at bright magnitudes to z 5.5 and that the principal effect of depth is to add objects at the magnitude limit. This indicates that high-redshift galaxies are compact in size (~01-03) and that large (04, 3 kpc) low surface brightness galaxies are rare. A simple comparison of the half-light radii of the Hubble Deep Field-North + Hubble Deep Field-South U-Dropouts with B-, V-, and i-Dropouts from the UDF shows that the sizes follow a (1 + z)-1.05±0.21 scaling toward high redshift. A more rigorous measurement compares different scalings of our U-dropout sample with the mean profiles for a set of intermediate-magnitude (26.0 < z850, AB < 27.5) i-Dropouts from the UDF. The best fit is found with a (1 + z) size scaling (for fixed luminosity). This result is then verified by repeating this experiment with different size measures, low-redshift samples, and magnitude ranges. Very similar scalings are found for all comparisons. A robust measurement of size evolution is thereby demonstrated for galaxies from z ~ 6 to 2.5 using data from the UDF.
Peng Qiu - One of the best experts on this subject based on the ideXlab platform.
-
embracing the Dropouts in single cell rna seq analysis
Nature Communications, 2020Co-Authors: Peng QiuAbstract:One primary reason that makes single-cell RNA-seq analysis challenging is Dropouts, where the data only captures a small fraction of the transcriptome of each cell. Almost all computational algorithms developed for single-cell RNA-seq adopted gene selection, dimension reduction or imputation to address the Dropouts. Here, an opposite view is explored. Instead of treating Dropouts as a problem to be fixed, we embrace it as a useful signal. We represent the dropout pattern by binarizing single-cell RNA-seq count data, and present a co-occurrence clustering algorithm to cluster cells based on the dropout pattern. We demonstrate in multiple published datasets that the binary dropout pattern is as informative as the quantitative expression of highly variable genes for the purpose of identifying cell types. We expect that recognizing the utility of Dropouts provides an alternative direction for developing computational algorithms for single-cell RNA-seq analysis. The analysis of RNA-seq data is complicated by Dropouts, and these are usually treated as a problem to be addressed. Here, Peng Qiu uses Dropouts as a source of information and presents a co-occurrence clustering algorithm to cluster cells based on the dropout pattern; this could be a complementary approach to existing methods.
Ivo Labbe - One of the best experts on this subject based on the ideXlab platform.
-
ultradeep infrared array camera observations of sub l z 7 and z 8 galaxies in the hubble ultra deep field the contribution of low luminosity galaxies to the stellar mass density and reionization
The Astrophysical Journal, 2010Co-Authors: Ivo Labbe, R J Bouwens, G D Illingworth, Valentino Gonzalez, Pascal Oesch, P G Van Dokkum, C M Carollo, Marijn Franx, M StiavelliAbstract:We study the Spitzer Infrared Array Camera (IRAC) mid-infrared (rest-frame optical) fluxes of 14 newly WFC3/IR-detected z ~ 7 z 850-dropout galaxies and 5z ~ 8 Y 105-dropout galaxies. The WFC3/IR depth and spatial resolution allow accurate removal of contaminating foreground light, enabling reliable flux measurements at 3.6 μm and 4.5 μm. None of the galaxies are detected to [3.6] 26.9 (AB, 2σ), but a stacking analysis reveals a robust detection for the z 850-Dropouts and an upper limit for the Y 105-Dropouts. We construct average broadband spectral energy distributions using the stacked Advanced Camera for Surveys (ACS), WFC3, and IRAC fluxes and fit stellar population synthesis models to derive mean redshifts, stellar masses, and ages. For the z 850-Dropouts, we find z = 6.9+0.1 –0.1, (U – V)rest 0.4, reddening AV = 0, stellar mass M* = 1.2+0.3 –0.6 × 109 M ☉ (Salpeter initial mass function). The best-fit ages ~300 Myr, M/LV 0.2, and SSFR ~1.7 Gyr–1 are similar to values reported for luminous z ~ 7 galaxies, indicating the galaxies are smaller but not much younger. The sub-L* galaxies observed here contribute significantly to the stellar mass density and under favorable conditions may have provided enough photons for sustained reionization at 7 < z < 11. In contrast, the z = 8.3+0.1 –0.2 Y 105-Dropouts have stellar masses that are uncertain by 1.5 dex due to the near-complete reliance on far-UV data. Adopting the 2σ upper limit on the M/L(z = 8), the stellar mass density to M UV,AB < –18 declines from ρ*(z = 7) = 3.7+1.4 –1.8 × 106 M ☉ Mpc–3 to ρ*(z = 8) < 8 × 105 M ☉ Mpc–3, following (1 + z)–6 over 3 < z < 8. Lower masses at z = 8 would signify more dramatic evolution, which can be established with deeper IRAC observations, long before the arrival of the James Webb Space Telescope.
-
ultradeep infrared array camera observations of sub l z 7 and z 8 galaxies in the hubble ultra deep field the contribution of low luminosity galaxies to the stellar mass density and reionization
arXiv: Cosmology and Nongalactic Astrophysics, 2009Co-Authors: Ivo Labbe, R J Bouwens, G D Illingworth, Valentino Gonzalez, Pascal Oesch, P G Van Dokkum, C M Carollo, Marijn Franx, M StiavelliAbstract:We study the Spitzer Infrared Array Camera (IRAC) mid-infrared (rest-frame optical) fluxes of 14 newly WFC3/IR-detected z=7 z_{850}-dropout galaxies and 5 z=8 Y_{105}-dropout galaxies. The WFC3/IR depth and spatial resolution allow accurate removal of contaminating foreground light, enabling reliable flux measurements at 3.6 micron and 4.5 micron. None of the galaxies are detected to [3.6]=26.9 (AB, 2 sigma), but a stacking analysis reveals a robust detection for the z_{850}-Dropouts and an upper limit for the Y_{105}-Dropouts. We construct average broadband SEDs using the stacked ACS, WFC3, and IRAC fluxes and fit stellar population synthesis models to derive mean redshifts, stellar masses, and ages. For the z_{850}-Dropouts, we find z=6.9^{+0.1}_{-0.1}, (U-V)_{rest}=0.4, reddening A_V=0, stellar mass M*=1.2^{+0.3}_{-0.6} x 10^9 M_sun (Salpeter IMF). The best-fit ages ~300Myr, M/L_V=0.2, and SSFR=1.7Gyr^{-1} are similar to values reported for luminous z=7 galaxies, indicating the galaxies are smaller but not younger. The sub-L* galaxies observed here contribute significantly to the stellar mass density and under favorable conditions may have provided enough photons for sustained reionization at 7
