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EVOLUTION OF INTRINSIC SCATTER IN THE SFR-STELLAR MASS CORRELATION AT 0.5 < <i>z</i> < 3
Kurczynski, Peter,Gawiser, Eric,Acquaviva, Viviana,Bell, Eric F.,Dekel, Avishai,de Mello, Duilia F.,Ferguson, Henry C.,Gardner, Jonathan P.,Grogin, Norman A.,Guo, Yicheng,Hopkins, Philip F.,Koekemoer, American Astronomical Society 2016 ASTROPHYSICAL JOURNAL LETTERS - Vol.820 No.1
<P>We present estimates of intrinsic scatter in the star formation rate (SFR)-stellar mass (M-*) correlation in the redshift range 0.5 < z < 3.0 and in the mass range 10(7) < M-* < 10(11)M(circle dot). We utilize photometry in the Hubble Ultradeep Field (HUDF12) and Ultraviolet Ultra Deep Field (UVUDF) campaigns and CANDELS/GOODS-S and estimate SFR, M-* from broadband spectral energy distributions and the best-available redshifts. The maximum depth of the UDF photometry (F160W 29.9 AB, 5 sigma depth) probes the SFR-M-* correlation down to M-* similar to 10(7)M(circle dot), a factor of 10-100x lower in M-* than previous studies, and comparable to dwarf galaxies in the local universe. We find the slope of the SFR-M-* relationship to be near unity at all redshifts and the normalization to decrease with cosmic time. We find a moderate increase in intrinsic scatter with cosmic time from 0.2 to 0.4 dex across the epoch of peak cosmic star formation. None of our redshift bins show a statistically significant increase in intrinsic scatter at low mass. However, it remains possible that intrinsic scatter increases at low mass on timescales shorter than similar to 100 Myr. Our results are consistent with a picture of gradual and self-similar assembly of galaxies across more than three orders of magnitude in stellar mass from as low as 10(7)M(circle dot).</P>
SURVEY DESIGN FOR SPECTRAL ENERGY DISTRIBUTION FITTING: A FISHER MATRIX APPROACH
Acquaviva, Viviana,Gawiser, Eric,Bickerton, Steven J.,Grogin, Norman A.,Guo, Yicheng,Lee, Seong-Kook IOP Publishing 2012 The Astrophysical journal Vol.749 No.1
<P>The spectral energy distribution (SED) of a galaxy contains information on the galaxy's physical properties, and multi-wavelength observations are needed in order to measure these properties via SED fitting. In planning these surveys, optimization of the resources is essential. The Fisher Matrix (FM) formalism can be used to quickly determine the best possible experimental setup to achieve the desired constraints on the SED-fitting parameters. However, because it relies on the assumption of a Gaussian likelihood function, it is in general less accurate than other slower techniques that reconstruct the probability distribution function (PDF) from the direct comparison between models and data. We compare the uncertainties on SED-fitting parameters predicted by the FM to the ones obtained using the more thorough PDF-fitting techniques. We use both simulated spectra and real data, and consider a large variety of target galaxies differing in redshift, mass, age, star formation history, dust content, and wavelength coverage. We find that the uncertainties reported by the two methods agree within a factor of two in the vast majority (similar to 90%) of cases. If the age determination is uncertain, the top-hat prior in age used in PDF fitting to prevent each galaxy from being older than the universe needs to be incorporated in the FM, at least approximately, before the two methods can be properly compared. We conclude that the FM is a useful tool for astronomical survey design.</P>
THE EVOLUTION OF STAR FORMATION HISTORIES OF QUIESCENT GALAXIES
Pacifici, Camilla,Kassin, Susan A.,Weiner, Benjamin J.,Holden, Bradford,Gardner, Jonathan P.,Faber, Sandra M.,Ferguson, Henry C.,Koo, David C.,Primack, Joel R.,Bell, Eric F.,Dekel, Avishai,Gawiser, Er American Astronomical Society 2016 The Astrophysical Journal Vol.832 No.1
<P>Although there has been much progress in understanding how galaxies evolve, we still do not understand how and when they stop forming stars and become quiescent. We address this by applying our galaxy spectral energy distribution models, which incorporate physically motivated star formation histories (SFHs) from cosmological simulations, to a sample of quiescent galaxies at 0.2 < z < 2.1. A total of 845 quiescent galaxies with multi-band photometry spanning rest-frame ultraviolet through near-infrared wavelengths are selected from the Cosmic Assembly Near-IR Deep Extragalactic Legacy Survey (CANDELS) data set. We compute median SFHs of these galaxies in bins of stellar mass and redshift. At all redshifts and stellar masses, the median SFHs rise, reach a peak, and then decline to reach quiescence. At high redshift, we find that the rise and decline are fast, as expected, because the universe is young. At low redshift, the duration of these phases depends strongly on stellar mass. Low-mass galaxies (log(M*/M-circle dot) similar to 9.5) grow on average slowly, take a long time to reach their peak of star formation (greater than or similar to 4 Gyr), and then the declining phase is fast (less than or similar to 2 Gyr). Conversely, high-mass galaxies (log(M*/M-circle dot) similar to 11) grow on average fast (less than or similar to 2 Gyr), and, after reaching their peak, decrease the star formation slowly (greater than or similar to 3). These findings are consistent with galaxy stellar mass being a driving factor in determining how evolved galaxies are, with high-mass galaxies being the most evolved at any time (i.e., downsizing). The different durations we observe in the declining phases also suggest that low- and high-mass galaxies experience different quenching mechanisms, which operate on different timescales.</P>