We have constructed a mass-selected sample of M ∗> 1011 M galaxies at 1 < z < 3 in the C... more We have constructed a mass-selected sample of M ∗> 1011 M galaxies at 1 < z < 3 in the CANDELS UDS and COSMOS fields and have decomposed these systems into their separate bulge and disk components according to their H160-band morphologies. By extending this analysis to multiple bands we have been able to conduct individual bulge and disk component SED fitting which has provided us with stellar-mass and star-formation rate estimates for the separate bulge and disk components. These have been combined with size measurements to explore the evolution of these massive high-redshift galaxies. By utilising the new decomposed stellar-mass estimates, we confirm that the bulge components display a stronger size evolution than the disks. This can be seen from both the fraction of bulge components which lie below the local relation and the median sizes of the bulge components, where the bulges are a median factor
We present the quantitative rest-frame B morphological evolution and galaxy merger fractions at 0... more We present the quantitative rest-frame B morphological evolution and galaxy merger fractions at 0.2 < z < 1.2 as observed by the All-wavelength Extended Groth Strip International Survey (AEGIS). We use the Gini coefficent and M20 to identify major mergers and classify galaxy morphology for a volume-limited sample of 3009 galaxies brighter than 0.4L ∗ B, assuming pure luminosity evolution of 1.3 MB per unit redshift. We find that the merger fraction remains roughly constant at 10 ± 2 % for 0.2 < z < 1.2. The fraction of E/S0/Sa increases from 21 ±3 % at z ∼ 1.1 to 44 ±9 % at z ∼ 0.3, while the fraction of Sb-Ir decreases from 64 ±6 % at z ∼ 1.1 to 47 ±9 % at z ∼ 0.3. The majority of z < 1.2 Spitzer MIPS 24 µm sources with L(IR)> 1011L ⊙ are disk galaxies, and only ∼ 15 % are classified as major merger candidates. Edge-on and dusty disk galaxies (Sb-Ir) are almost a third of the red sequence at z ∼ 1.1, while E/S0/Sa make up over 90 % of the red sequence at z ∼ 0.3. ...
Based on observations taken at the W. M. Keck Observatory which is operated jointly by the Univer... more Based on observations taken at the W. M. Keck Observatory which is operated jointly by the University
We study the evolution of the core (r<1 kpc) and effective (r<r_e) stellar-mass surface den... more We study the evolution of the core (r<1 kpc) and effective (r<r_e) stellar-mass surface densities, in star-forming and quiescent galaxies. Since z=3, both populations occupy distinct, linear relations in log(Sigma_e) and log(Sigma_1) vs. log(M). These structural relations exhibit slopes and scatter that remain almost constant with time while their normalizations decline. For SFGs, the normalization declines by less than a factor of 2 from z=3, in both Sigma_e and Sigma_1. Such mild declines suggest that SFGs build dense cores by growing along these relations. We define this evolution as the structural main sequence (Sigma-MS). Quiescent galaxies follow different relations (Sigma^Q_e, Sigma^Q_1) off the Sigma-MS by having higher densities than SFGs of the same mass and redshift. The normalization of Sigma^Q_e declines by a factor of 10 since z=3, but only a factor of 2 in Sigma^Q_1. Thus, the common denominator for quiescent galaxies at all redshifts is the presence of a dense ...
We describe the dynamical properties which may be inferred f om HST/STIS spectroscopic observatio... more We describe the dynamical properties which may be inferred f om HST/STIS spectroscopic observations of luminous compact blue galax ies (LCBGs) between0.1 < z < 0.7. While the sample is homogeneous in blue rest-frame color, small size and line-width, and high surface-brightn ess, their detailed morphology is eclectic. Here we determine the amplitude of rota ti n versus random, or disturbed motions of the ionized gas. This information af firms the accuracy of dynamical mass and M/L estimates from Keck integrated linewidths, and hence also the predictions of the photometric fading of these unus al galaxies. The resolved kinematics indicates this small subset of LCBGs ar e dynamically hot, and unlikely to be embedded in disk systems.
We study the nature of faint blue compact galaxies (BCGs) at redshifts z 0:2 ? 1:3. Most distant ... more We study the nature of faint blue compact galaxies (BCGs) at redshifts z 0:2 ? 1:3. Most distant BCGs have masses M < 10 10 M , i.e., they are dwarf stellar systems. The majority of these galaxies have colors, sizes, surface brightnesses, luminosities, velocity widths, excitations, star formation rates (SFR), and mass-to-light ratios characteristic of nearby young HII galaxies. The more massive BCGs form a more heterogeneous class of evolved starbursts, similar to local disk starburst galaxies. Without additional star formation, HII-like BCGs will most likely fade to resemble today's spheroidal galaxies such as NGC 205. From the comparison with the global comoving SFR densities derived from previous data sets, we conclude that BCGs, though only 20% of the general eld population, may contribute as much as 45% to the global SFR density of the universe at z < 1.
Monthly Notices of the Royal Astronomical Society, 2021
We study how mock-observed stellar morphological and structural properties of massive galaxies ar... more We study how mock-observed stellar morphological and structural properties of massive galaxies are built up between z = 0.5 and z = 3 in the TNG50 cosmological simulation. We generate mock images with the properties of the CANDELS survey and derive Sersic parameters and optical rest-frame morphologies as usually done in the observations. Overall, the simulation reproduces the observed evolution of the abundances of different galaxy morphological types of star-forming and quiescent galaxies. The log M* − log Re and log M* − log Σ1 relations of the simulated star-forming and quenched galaxies also match the observed slopes and zeropoints to within 1-σ. In the simulation, galaxies increase their observed central stellar mass density (Σ1) and transform in morphology from irregular/clumpy systems to normal Hubble-type systems in the Star Formation Main Sequence at a characteristic stellar mass of ∼1010.5 M⊙ which is reflected in an increase of the central stellar mass density (Σ1). This ...
Symposium - International Astronomical Union, 1996
Data from the Keck and Hubble Space Telescopes have been combined to explore the nature of very f... more Data from the Keck and Hubble Space Telescopes have been combined to explore the nature of very faint I > 22 field galaxies. At a redshift z ∼ 1, such galaxies have luminosities similar to that of typical galaxies today. Though small, our sample of 33 redshifts already suggest that the median redshift for I > 22 galaxies is higher than the z = 0.6 expected for the “maximum merger model” of Carlberg (1995). At redshifts z > 0.8, mergers, interactions, and infall of minor galaxies into larger hosts appear to be common events; a wide diversity of morphological types existed; and some stellar populations were already so red that their major formation epoch occurred at redshifts z > 2.
We have constructed a mass-selected sample of M ∗> 1011 M galaxies at 1 < z < 3 in the C... more We have constructed a mass-selected sample of M ∗> 1011 M galaxies at 1 < z < 3 in the CANDELS UDS and COSMOS fields and have decomposed these systems into their separate bulge and disk components according to their H160-band morphologies. By extending this analysis to multiple bands we have been able to conduct individual bulge and disk component SED fitting which has provided us with stellar-mass and star-formation rate estimates for the separate bulge and disk components. These have been combined with size measurements to explore the evolution of these massive high-redshift galaxies. By utilising the new decomposed stellar-mass estimates, we confirm that the bulge components display a stronger size evolution than the disks. This can be seen from both the fraction of bulge components which lie below the local relation and the median sizes of the bulge components, where the bulges are a median factor
We present the quantitative rest-frame B morphological evolution and galaxy merger fractions at 0... more We present the quantitative rest-frame B morphological evolution and galaxy merger fractions at 0.2 < z < 1.2 as observed by the All-wavelength Extended Groth Strip International Survey (AEGIS). We use the Gini coefficent and M20 to identify major mergers and classify galaxy morphology for a volume-limited sample of 3009 galaxies brighter than 0.4L ∗ B, assuming pure luminosity evolution of 1.3 MB per unit redshift. We find that the merger fraction remains roughly constant at 10 ± 2 % for 0.2 < z < 1.2. The fraction of E/S0/Sa increases from 21 ±3 % at z ∼ 1.1 to 44 ±9 % at z ∼ 0.3, while the fraction of Sb-Ir decreases from 64 ±6 % at z ∼ 1.1 to 47 ±9 % at z ∼ 0.3. The majority of z < 1.2 Spitzer MIPS 24 µm sources with L(IR)> 1011L ⊙ are disk galaxies, and only ∼ 15 % are classified as major merger candidates. Edge-on and dusty disk galaxies (Sb-Ir) are almost a third of the red sequence at z ∼ 1.1, while E/S0/Sa make up over 90 % of the red sequence at z ∼ 0.3. ...
Based on observations taken at the W. M. Keck Observatory which is operated jointly by the Univer... more Based on observations taken at the W. M. Keck Observatory which is operated jointly by the University
We study the evolution of the core (r<1 kpc) and effective (r<r_e) stellar-mass surface den... more We study the evolution of the core (r<1 kpc) and effective (r<r_e) stellar-mass surface densities, in star-forming and quiescent galaxies. Since z=3, both populations occupy distinct, linear relations in log(Sigma_e) and log(Sigma_1) vs. log(M). These structural relations exhibit slopes and scatter that remain almost constant with time while their normalizations decline. For SFGs, the normalization declines by less than a factor of 2 from z=3, in both Sigma_e and Sigma_1. Such mild declines suggest that SFGs build dense cores by growing along these relations. We define this evolution as the structural main sequence (Sigma-MS). Quiescent galaxies follow different relations (Sigma^Q_e, Sigma^Q_1) off the Sigma-MS by having higher densities than SFGs of the same mass and redshift. The normalization of Sigma^Q_e declines by a factor of 10 since z=3, but only a factor of 2 in Sigma^Q_1. Thus, the common denominator for quiescent galaxies at all redshifts is the presence of a dense ...
We describe the dynamical properties which may be inferred f om HST/STIS spectroscopic observatio... more We describe the dynamical properties which may be inferred f om HST/STIS spectroscopic observations of luminous compact blue galax ies (LCBGs) between0.1 < z < 0.7. While the sample is homogeneous in blue rest-frame color, small size and line-width, and high surface-brightn ess, their detailed morphology is eclectic. Here we determine the amplitude of rota ti n versus random, or disturbed motions of the ionized gas. This information af firms the accuracy of dynamical mass and M/L estimates from Keck integrated linewidths, and hence also the predictions of the photometric fading of these unus al galaxies. The resolved kinematics indicates this small subset of LCBGs ar e dynamically hot, and unlikely to be embedded in disk systems.
We study the nature of faint blue compact galaxies (BCGs) at redshifts z 0:2 ? 1:3. Most distant ... more We study the nature of faint blue compact galaxies (BCGs) at redshifts z 0:2 ? 1:3. Most distant BCGs have masses M < 10 10 M , i.e., they are dwarf stellar systems. The majority of these galaxies have colors, sizes, surface brightnesses, luminosities, velocity widths, excitations, star formation rates (SFR), and mass-to-light ratios characteristic of nearby young HII galaxies. The more massive BCGs form a more heterogeneous class of evolved starbursts, similar to local disk starburst galaxies. Without additional star formation, HII-like BCGs will most likely fade to resemble today's spheroidal galaxies such as NGC 205. From the comparison with the global comoving SFR densities derived from previous data sets, we conclude that BCGs, though only 20% of the general eld population, may contribute as much as 45% to the global SFR density of the universe at z < 1.
Monthly Notices of the Royal Astronomical Society, 2021
We study how mock-observed stellar morphological and structural properties of massive galaxies ar... more We study how mock-observed stellar morphological and structural properties of massive galaxies are built up between z = 0.5 and z = 3 in the TNG50 cosmological simulation. We generate mock images with the properties of the CANDELS survey and derive Sersic parameters and optical rest-frame morphologies as usually done in the observations. Overall, the simulation reproduces the observed evolution of the abundances of different galaxy morphological types of star-forming and quiescent galaxies. The log M* − log Re and log M* − log Σ1 relations of the simulated star-forming and quenched galaxies also match the observed slopes and zeropoints to within 1-σ. In the simulation, galaxies increase their observed central stellar mass density (Σ1) and transform in morphology from irregular/clumpy systems to normal Hubble-type systems in the Star Formation Main Sequence at a characteristic stellar mass of ∼1010.5 M⊙ which is reflected in an increase of the central stellar mass density (Σ1). This ...
Symposium - International Astronomical Union, 1996
Data from the Keck and Hubble Space Telescopes have been combined to explore the nature of very f... more Data from the Keck and Hubble Space Telescopes have been combined to explore the nature of very faint I > 22 field galaxies. At a redshift z ∼ 1, such galaxies have luminosities similar to that of typical galaxies today. Though small, our sample of 33 redshifts already suggest that the median redshift for I > 22 galaxies is higher than the z = 0.6 expected for the “maximum merger model” of Carlberg (1995). At redshifts z > 0.8, mergers, interactions, and infall of minor galaxies into larger hosts appear to be common events; a wide diversity of morphological types existed; and some stellar populations were already so red that their major formation epoch occurred at redshifts z > 2.
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