Seong-Kook Lee

THE ESTIMATION OF STAR FORMATION RATES AND STELLAR POPULATION AGES OF HIGH-REDSHIFT GALAXIES FROM BROADBAND PHOTOMETRY

We explore methods to improve the estimates of star formation rates and mean stellar population ages from broadband photometry of high-redshift star-forming galaxies. We use synthetic spectral templates with a variety of simple parametric star formation histories to fit broadband spectral energy distributions. These parametric models are used to infer ages, star formation rates, and stellar masses for a mock data set drawn from a hierarchical semi-analytic model of galaxy evolution. Traditional parametric models generally assume an exponentially declining rate of star formation after an initial instantaneous rise. Our results show that star formation histories with a much more gradual rise in the star formation rate are likely to be better templates, and are likely to give better overall estimates of the age distribution and star formation rate distribution of Lyman break galaxies (LBGs). For B- and V-dropouts, we find the best simple parametric model to be one where the star formation rate increases linearly with time. The exponentially declining model overpredicts the age by 100% and 120% for B- and V-dropouts, on average, while for a linearly increasing model, the age is overpredicted by 9% and 16%, respectively. Similarly, the exponential model underpredicts star formation rates by 56% and 60%, while the linearly increasing model underpredicts by 15% and 22%, respectively. For U-dropouts, the models where the star formation rate has a peak (near z ~ 3) provide the best match for age—overprediction is reduced from 110% to 26%—and star formation rate—underprediction is reduced from 58% to 22%. We classify different types of star formation histories in the semi-analytic models and show how the biases behave for the different classes. We also provide two-band calibration formulae for stellar mass and star formation rate estimations.

THE EVOLUTION OF THE GALAXY STELLAR MASS FUNCTION AT z = 4–8: A STEEPENING LOW-MASS-END SLOPE WITH INCREASING REDSHIFT

We present galaxy stellar mass functions (GSMFs) at

REST-FRAME UV-OPTICALLY SELECTED GALAXIES AT 2.3 ≲ z ≲ 3.5: SEARCHING FOR DUSTY STAR-FORMING AND PASSIVELY EVOLVING GALAXIES

z=

EVOLUTION OF STAR FORMATION PROPERTIES OF HIGH-REDSHIFT CLUSTER GALAXIES SINCE z = 2

4-8 from a rest-frame ultraviolet (UV) selected sample of

DISCOVERY OF A FAINT QUASAR AT z ∼ 6 AND IMPLICATIONS FOR COSMIC REIONIZATION

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Distance and Properties of NGC 4993 as the Host Galaxy of the Gravitational-wave Source GW170817

4500 galaxies, found via photometric redshifts over an area of

The Infrared Medium-Deep Survey. II. How to Trigger Radio AGNs? Hints from their Environments

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Linking Galaxies to Dark Matter Halos at z ~ 1 : Dependence of Galaxy Clustering on Stellar Mass and Specific Star Formation Rate

280 arcmin

SURVEY DESIGN FOR SPECTRAL ENERGY DISTRIBUTION FITTING: A FISHER MATRIX APPROACH

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The Infrared Medium-deep Survey. III. Survey of Luminous Quasars at 4.7 ≤ z ≤ 5.4

in the CANDELS/GOODS fields and the Hubble Ultra Deep Field. The deepest Spitzer/IRAC data yet-to-date and the relatively large volume allow us to place a better constraint at both the low- and high-mass ends of the GSMFs compared to previous space-based studies from pre-CANDELS observations. Supplemented by a stacking analysis, we find a linear correlation between the rest-frame UV absolute magnitude at 1500 A (