Publications (3)0 Total impact
-
Article: Newly-quenched galaxies as the cause for the apparent evolution in average size of the population
[show abstract] [hide abstract]
ABSTRACT: We study the number densities of quenched early-type galaxies (Q-ETGs) of a given size in a homogeneous COSMOS sample over the interval 1 < z < 0.2. At 10^{10.5}<M<10^{11} Msun we see no change in the number density of compact Q-ETGs, while at >10^{11} Msun we find a decrease by 30-40%. In both mass bins, the increase of the median sizes of Q-ETGs with time is primarily caused by the addition of larger Q-ETGs. At all masses, compact Q-ETGs become redder towards later epochs, with a (U-V) color difference which is consistent with a passive evolution of their stellar populations. At all epochs, the larger Q-ETGs have colors that are systematically bluer than those of the more compact Q-ETGs, suggesting that the former are younger than the latter. The sizes and number of the star-forming galaxies over the same redshift interval also support the idea that new Q-ETGs are responsible for the growth in the median size of the population at a given mass. The sizes of the new members of the population appear to scale as roughly (1+z)^{-1}. We conclude that the dominant cause of the apparent size evolution of the population of Q-ETGs is the addition at later epochs of larger galaxies. [abridged]02/2013; -
Article: Bars in early- and late-type disks in COSMOS
[show abstract] [hide abstract]
ABSTRACT: We investigate the (large-scale) bar fraction in a mass-complete sample of M > 10^10.5 Msun disk galaxies at 0.2 < z < 0.6 in the COSMOS field. The fraction of barred disks strongly depends on mass, disk morphology, and specific star formation rate (SSFR). At intermediate stellar mass (10^10.5 < M < 10^11 Msun) the bar fraction in early-type disks is much higher, at all redshifts, by a factor ~2, than that in late-type disks. This trend is reversed at higher stellar mass (M > 10^11 Msun), where the fraction of bars in early-type disks becomes significantly lower, at all redshifts, than that in late-type disks. The bar fractions for galaxies with low and high SSFRs closely follow those of the morphologically-selected early-type and late-type populations, respectively. This indicates a close correspondence between morphology and SSFR in disk galaxies at these earlier epochs. Interestingly, the total bar fraction in 10^10.5 < M < 10^11 Msun disks is built up by a factor of ~2 over the redshift interval explored, while for M > 10^11 Msun disks it remains roughly constant. This indicates that, already by z ~ 0.6, spectral and morphological transformations in the most massive disk galaxies have largely converged to the familiar Hubble sequence that we observe in the local Universe, while for intermediate mass disks this convergence is ongoing until at least z ~ 0.2. Moreover, these results highlight the importance of employing mass-limited samples for quantifying the evolution of barred galaxies. Finally, the evolution of the barred galaxy populations investigated does not depend on the large-scale environmental density (at least, on the scales which can be probed with the available photometric redshifts). Comment: 10 pages, 4 figures, updated to reflect version accepted by MNRAS01/2010; -
Article: Bars in early- and late-type discs in COSMOS
[show abstract] [hide abstract]
ABSTRACT: We investigate the (large-scale) bar fraction in a mass-complete sample of M > 10^(10.5) M_⊙ disc galaxies at 0.2 < z < 0.6 in the Cosmological Evolution Survey (COSMOS) field. The fraction of barred discs strongly depends on mass, disc morphology and specific star formation rate (SSFR). At intermediate stellar mass (10^(10.5) < M < 10^(11) M_⊙) the bar fraction in early-type discs is much higher, at all redshifts, by a factor of ~2, than that in late-type discs. This trend is reversed at higher stellar mass (M > 10^(11) M_⊙), where the fraction of bars in early-type discs becomes significantly lower, at all redshifts, than that in late-type discs. The bar fractions for galaxies with low and high SSFRs closely follow those of the morphologically selected early- and late-type populations, respectively. This indicates a close correspondence between morphology and SSFR in disc galaxies at these earlier epochs. Interestingly, the total bar fraction in 10^(10.5) < M < 10^(11) M_⊙ discs is built up by a factor of ~2 over the redshift interval explored, while for M > 10^(11) M_⊙ discs it remains roughly constant. This indicates that, already by z ~ 0.6, spectral and morphological transformations in the most massive disc galaxies have largely converged to the familiar Hubble sequence that we observe in the local Universe, while for intermediate-mass discs this convergence is ongoing until at least z ~ 0.2. Moreover, these results highlight the importance of employing mass-limited samples for quantifying the evolution of barred galaxies. Finally, the evolution of the barred galaxy populations investigated does not depend on the large-scale environmental density (at least, on the scales which can be probed with the available photometric redshifts).
