Using stellar kinematics measurements, we investigate the growth of massive, quiescent galaxies from z ~{} 2 to today. We present X-Shooter spectra from the UV to NIR and dynamical mass... Show moreUsing stellar kinematics measurements, we investigate the growth of massive, quiescent galaxies from z ~{} 2 to today. We present X-Shooter spectra from the UV to NIR and dynamical mass measurements of five quiescent massive ({gt}10$^{11}$ M $_{⊙}$) galaxies at z ~{} 2. This triples the sample of z {gt} 1.5 galaxies with well-constrained ({$delta$}{$σ$} {lt} 100 km s$^{-1}$) velocity dispersion measurements. From spectral population synthesis modeling we find that these galaxies have stellar ages that range from 0.5 to 2 Gyr, with no signs of ongoing star formation. We measure velocity dispersions (290-450 km s$^{-1}$) from stellar absorption lines and find that they are 1.6-2.1 times higher than those of galaxies in the Sloan Digital Sky Survey at the same mass. Sizes are measured using GALFIT from Hubble Space Telescope Wide Field Camera 3 H $_{160}$ and UDS K-band images. The dynamical masses correspond well to the spectral energy distribution based stellar masses, with dynamical masses that are ~{}15% higher. We find that M $_{*}$/M $_{dyn}$ may decrease slightly with time, which could reflect the increase of the dark matter fraction within an increasing effective radius. We combine different stellar kinematic studies from the literature and examine the structural evolution from z ~{} 2 to z ~{} 0: we confirm that at fixed dynamical mass, the effective radius increases by a factor of ~{}2.8, and the velocity dispersion decreases by a factor of ~{}1.7. The mass density within one effective radius decreases by a factor of ~{}20, while within a fixed physical radius (1 kpc) it decreases only mildly (factor of ~{}2). When we allow for an evolving mass limit by selecting a population of galaxies at fixed number density, a stronger size growth with time is found (factor of ~{}4), velocity dispersion decreases by a factor of ~{}1.4, and interestingly, the mass density within 1 kpc is consistent with no evolution. This finding suggests that massive quiescent galaxies at z ~{} 2 grow inside out, consistent with the expectations from minor mergers. Show less
Sande, J. van de; Kriek, M.; Franx, M.; Dokkum, P. van; Bezanson, R.; Bouwens, R.J.; ... ; Skelton, R. 2013
Using stellar kinematics measurements, we investigate the growth of massive, quiescent galaxies from z ~{} 2 to today. We present X-Shooter spectra from the UV to NIR and dynamical mass... Show moreUsing stellar kinematics measurements, we investigate the growth of massive, quiescent galaxies from z ~{} 2 to today. We present X-Shooter spectra from the UV to NIR and dynamical mass measurements of five quiescent massive ({gt}10$^{11}$ M $_{⊙}$) galaxies at z ~{} 2. This triples the sample of z {gt} 1.5 galaxies with well-constrained ({$delta$}{$σ$} {lt} 100 km s$^{-1}$) velocity dispersion measurements. From spectral population synthesis modeling we find that these galaxies have stellar ages that range from 0.5 to 2 Gyr, with no signs of ongoing star formation. We measure velocity dispersions (290-450 km s$^{-1}$) from stellar absorption lines and find that they are 1.6-2.1 times higher than those of galaxies in the Sloan Digital Sky Survey at the same mass. Sizes are measured using GALFIT from Hubble Space Telescope Wide Field Camera 3 H $_{160}$ and UDS K-band images. The dynamical masses correspond well to the spectral energy distribution based stellar masses, with dynamical masses that are ~{}15% higher. We find that M $_{*}$/M $_{dyn}$ may decrease slightly with time, which could reflect the increase of the dark matter fraction within an increasing effective radius. We combine different stellar kinematic studies from the literature and examine the structural evolution from z ~{} 2 to z ~{} 0: we confirm that at fixed dynamical mass, the effective radius increases by a factor of ~{}2.8, and the velocity dispersion decreases by a factor of ~{}1.7. The mass density within one effective radius decreases by a factor of ~{}20, while within a fixed physical radius (1 kpc) it decreases only mildly (factor of ~{}2). When we allow for an evolving mass limit by selecting a population of galaxies at fixed number density, a stronger size growth with time is found (factor of ~{}4), velocity dispersion decreases by a factor of ~{}1.4, and interestingly, the mass density within 1 kpc is consistent with no evolution. This finding suggests that massive quiescent galaxies at z ~{} 2 grow inside out, consistent with the expectations from minor mergers. Show less
Muzzin, A.V.; Marchesini, D.; Stefanon, M.; Franx, M.; McCracken, H.; Milvang-Jensen, B.; ... ; Dokkum, P. van 2013
We present measurements of the stellar mass functions (SMFs) of star-forming and quiescent galaxies to z = 4 using a sample of 95,675 K$_s$ -selected galaxies in the COSMOS/UltraVISTA field. The... Show moreWe present measurements of the stellar mass functions (SMFs) of star-forming and quiescent galaxies to z = 4 using a sample of 95,675 K$_s$ -selected galaxies in the COSMOS/UltraVISTA field. The SMFs of the combined population are in good agreement with previous measurements and show that the stellar mass density of the universe was only 50%, 10%, and 1% of its current value at z ~{} 0.75, 2.0, and 3.5, respectively. The quiescent population drives most of the overall growth, with the stellar mass density of these galaxies increasing as {$ρ$}$_{star}$vprop(1 + z)$^{–4.7 ± 0.4}$ since z = 3.5, whereas the mass density of star-forming galaxies increases as {$ρ$}$_{star}$vprop(1 + z)$^{–2.3 ± 0.2}$. At z {gt} 2.5, star-forming galaxies dominate the total SMF at all stellar masses, although a non-zero population of quiescent galaxies persists to z = 4. Comparisons of the K$_s$ -selected star-forming galaxy SMFs with UV-selected SMFs at 2.5 {lt} z {lt} 4 show reasonable agreement and suggest that UV-selected samples are representative of the majority of the stellar mass density at z {gt} 3.5. We estimate the average mass growth of individual galaxies by selecting galaxies at fixed cumulative number density. The average galaxy with log(M $_{star}$/M $_{☉}$) = 11.5 at z = 0.3 has grown in mass by only 0.2 dex (0.3 dex) since z = 2.0 (3.5), whereas those with log(M $_{star}$/M $_{☉}$) = 10.5 have grown by {gt}1.0 dex since z = 2. At z {lt} 2, the time derivatives of the mass growth are always larger for lower-mass galaxies, which demonstrates that the mass growth in galaxies since that redshift is mass-dependent and primarily bottom-up. Lastly, we examine potential sources of systematic uncertainties in the SMFs and find that those from photo-z templates, stellar population synthesis modeling, and the definition of quiescent galaxies dominate the total error budget in the SMFs. Based on data products from observations made with ESO Telescopes at the La Silla Paranal Observatory under ESO programme ID 179.A-2005 and on data products produced by TERAPIX and the Cambridge Astronomy Survey Unit on behalf of the UltraVISTA consortium. Show less
Patel, S.G.; Fumagalli, M.; Franx, M.; Dokkum, P. van; Wel, A. van der; Leja, J.; ... ; Rix, H. 2013
We follow the structural evolution of star-forming galaxies (SFGs) like the Milky Way by selecting progenitors to z ~{} 1.3 based on the stellar mass growth inferred from the evolution of the star... Show moreWe follow the structural evolution of star-forming galaxies (SFGs) like the Milky Way by selecting progenitors to z ~{} 1.3 based on the stellar mass growth inferred from the evolution of the star-forming sequence. We select our sample from the 3D-HST survey, which utilizes spectroscopy from the HST/WFC3 G141 near-IR grism and enables precise redshift measurements for our sample of SFGs. Structural properties are obtained from Sérsic profile fits to CANDELS WFC3 imaging. The progenitors of z = 0 SFGs with stellar mass M = 10$^{10.5}$ M $_{☉}$ are typically half as massive at z ~{} 1. This late-time stellar mass growth is consistent with recent studies that employ abundance matching techniques. The descendant SFGs at z ~{} 0 have grown in half-light radius by a factor of ~{}1.4 since z ~{} 1. The half-light radius grows with stellar mass as r$_e$ vpropM $^{0.29}$. While most of the stellar mass is clearly assembling at large radii, the mass surface density profiles reveal ongoing mass growth also in the central regions where bulges and pseudobulges are common features in present day late-type galaxies. Some portion of this growth in the central regions is due to star formation as recent observations of H{$α$} maps for SFGs at z ~{} 1 are found to be extended but centrally peaked. Connecting our lookback study with galactic archeology, we find the stellar mass surface density at R = 8 kpc to have increased by a factor of ~{}2 since z ~{} 1, in good agreement with measurements derived for the solar neighborhood of the Milky Way. Based on observations made with the NASA/ESA Hubble Space Telescope, obtained at the Space Telescope Science Institute. STScI is operated by the Association of Universities for Research in Astronomy, Inc. under NASA contract NAS 5-26555. Show less
Muzzin, A.V.; Labbé, I.F.L.; Franx, M.; Dokkum, P. van; Holt, J.; Szomoru, D.; ... ; Milvang-Jensen, B. 2012
![Rest-frame Optical Emission Lines in z ~ 3.5 Lyman-break-selected Galaxies: The Ubiquity of Unusually High [OIII]/Hβ Ratios at 2 Gyr](/sites/all/modules/custom/islandora_solr_search/images/defaultimg.png?solr_nav%5Bid%5D=cd8337e3c999dd8d3ef3&solr_nav%5Bpage%5D=1&solr_nav%5Boffset%5D=10)
