Dynamical masses of early-type galaxies at z ∼ 2: Are they truly superdense?
We measured stellar velocity dispersions σ and derived dynamical masses of nine massive (M ≈ 1011 M ⊙) early-type galaxies (ETGs) from the Galaxy Mass Assembly ultra-deep Spectroscopic Survey (GMASS) sample at redshift 1.4 ≲ z ≲ 2.0. The σ are based on individual spectra for two galaxies at z ≈ 1.4...
| Main Authors: | , , , , , , , , , , , , , |
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| Format: | Journal article |
| Language: | English |
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Institute of Physics Publishing
2009
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| _version_ | 1826297117033889792 |
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| author | Cappellari, M Di Serego Alighieri, S Cimatti, A Daddi, E Renzini, A Kurk, J Cassata, P Dickinson, M Franceschini, A Mignoli, M Pozzetti, L Rodighiero, G Rosati, P Zamorani, G |
| author_facet | Cappellari, M Di Serego Alighieri, S Cimatti, A Daddi, E Renzini, A Kurk, J Cassata, P Dickinson, M Franceschini, A Mignoli, M Pozzetti, L Rodighiero, G Rosati, P Zamorani, G |
| author_sort | Cappellari, M |
| collection | OXFORD |
| description | We measured stellar velocity dispersions σ and derived dynamical masses of nine massive (M ≈ 1011 M ⊙) early-type galaxies (ETGs) from the Galaxy Mass Assembly ultra-deep Spectroscopic Survey (GMASS) sample at redshift 1.4 ≲ z ≲ 2.0. The σ are based on individual spectra for two galaxies at z ≈ 1.4 and on a stacked spectrum for seven galaxies with 1.6 < z < 2.0, with 202 hr of exposure at the ESO Very Large Telescope. We constructed detailed axisymmetric dynamical models for the objects, based on the Jeans equations, taking the observed surface brightness (from deep HST/ACS observations), point-spread function, and slit effects into account. Our dynamical masses M Jeans agree within ≲30% with virial estimates M vir = 5 × Reσ2/ G, although the latter tend to be smaller. Our M Jeans also agrees within a factor ≲2 with the M pop previously derived using stellar population models and 11 bands photometry. This confirms that the galaxies are intrinsically massive. The inferred mass-to-light ratios (M/L) U in the very age-sensitive rest-frame U band are consistent with passive evolution in the past 1 Gyr (formation redshift zf ∼3). A "bottom-light" stellar initial mass function appears to be required to ensure close agreement between M Jeans and M pop at z ∼2, as it does at z ∼0. The GMASS ETGs are on average more dense than their local counterpart. However, a few percent of local ETGs of similar dynamical masses also have comparable σ and mass surface density Σ50 inside R e. © 2009. The American Astronomical Society. All rights reserved. |
| first_indexed | 2024-03-07T04:26:40Z |
| format | Journal article |
| id | oxford-uuid:cce096c7-e83c-4718-a047-700ec39aa39d |
| institution | University of Oxford |
| language | English |
| last_indexed | 2024-03-07T04:26:40Z |
| publishDate | 2009 |
| publisher | Institute of Physics Publishing |
| record_format | dspace |
| spelling | oxford-uuid:cce096c7-e83c-4718-a047-700ec39aa39d2022-03-27T07:24:53ZDynamical masses of early-type galaxies at z ∼ 2: Are they truly superdense?Journal articlehttp://purl.org/coar/resource_type/c_dcae04bcuuid:cce096c7-e83c-4718-a047-700ec39aa39dEnglishSymplectic Elements at OxfordInstitute of Physics Publishing2009Cappellari, MDi Serego Alighieri, SCimatti, ADaddi, ERenzini, AKurk, JCassata, PDickinson, MFranceschini, AMignoli, MPozzetti, LRodighiero, GRosati, PZamorani, GWe measured stellar velocity dispersions σ and derived dynamical masses of nine massive (M ≈ 1011 M ⊙) early-type galaxies (ETGs) from the Galaxy Mass Assembly ultra-deep Spectroscopic Survey (GMASS) sample at redshift 1.4 ≲ z ≲ 2.0. The σ are based on individual spectra for two galaxies at z ≈ 1.4 and on a stacked spectrum for seven galaxies with 1.6 < z < 2.0, with 202 hr of exposure at the ESO Very Large Telescope. We constructed detailed axisymmetric dynamical models for the objects, based on the Jeans equations, taking the observed surface brightness (from deep HST/ACS observations), point-spread function, and slit effects into account. Our dynamical masses M Jeans agree within ≲30% with virial estimates M vir = 5 × Reσ2/ G, although the latter tend to be smaller. Our M Jeans also agrees within a factor ≲2 with the M pop previously derived using stellar population models and 11 bands photometry. This confirms that the galaxies are intrinsically massive. The inferred mass-to-light ratios (M/L) U in the very age-sensitive rest-frame U band are consistent with passive evolution in the past 1 Gyr (formation redshift zf ∼3). A "bottom-light" stellar initial mass function appears to be required to ensure close agreement between M Jeans and M pop at z ∼2, as it does at z ∼0. The GMASS ETGs are on average more dense than their local counterpart. However, a few percent of local ETGs of similar dynamical masses also have comparable σ and mass surface density Σ50 inside R e. © 2009. The American Astronomical Society. All rights reserved. |
| spellingShingle | Cappellari, M Di Serego Alighieri, S Cimatti, A Daddi, E Renzini, A Kurk, J Cassata, P Dickinson, M Franceschini, A Mignoli, M Pozzetti, L Rodighiero, G Rosati, P Zamorani, G Dynamical masses of early-type galaxies at z ∼ 2: Are they truly superdense? |
| title | Dynamical masses of early-type galaxies at z ∼ 2: Are they truly superdense? |
| title_full | Dynamical masses of early-type galaxies at z ∼ 2: Are they truly superdense? |
| title_fullStr | Dynamical masses of early-type galaxies at z ∼ 2: Are they truly superdense? |
| title_full_unstemmed | Dynamical masses of early-type galaxies at z ∼ 2: Are they truly superdense? |
| title_short | Dynamical masses of early-type galaxies at z ∼ 2: Are they truly superdense? |
| title_sort | dynamical masses of early type galaxies at z ∼ 2 are they truly superdense |
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