Abstract
Several recent studies find that 10%-50% of morphologically selected field early-type galaxies at redshifts z ≲ 1 have blue colors indicative of recent star formation. Such "blue spheroids" might be massive early-type galaxies with active star formation, perhaps induced by recent merger events. Alternatively, they could be starbursting, low-mass spheroids. To distinguish between these two choices, we have selected 10 "Blue Spheroid Candidates" (BSCs) from a quantitatively selected E/S0 sample to study their properties, including kinematics from Keck spectra obtained as part of the DEEP Groth Strip Survey (GSS). Most BSCs (70%) turn out to belong to two broad categories, while the remaining objects are likely to be misclassified objects. Type 1 BSCs have underlying red stellar components with bluer inner components. Type 2 BSCs do not show an obvious sign of the underlying red stellar component, and their overall colors are quite blue [(U - B)rest < 0]. Both type 1 and type 2 BSCs have internal velocity dispersions measured from emission lines σ ≲ 80 km s-1 and estimated dynamical masses of only a few × 1010 M⊙ or less. For type 1 BSCs, we estimate σ of the red component using the fundamental plane relation of distant field absorption-line galaxies and find that these σ estimates are similar to the σ measured from emission lines. Overall, we conclude that our type 1 and type 2 BSCs are more likely to be star-forming low-mass spheroids than star-forming, massive, early-type galaxies.
Original language | English (US) |
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Pages (from-to) | 750-763 |
Number of pages | 14 |
Journal | Astronomical Journal |
Volume | 122 |
Issue number | 2 |
DOIs | |
State | Published - Aug 2001 |
Externally published | Yes |
Keywords
- Cosmology: observations
- Galaxies : elliptical and lenticular, cD
- Galaxies: dwarf
- Galaxies: evolution
- Galaxies: formation
- Galaxies: high-redshift
- Galaxies: kinematics and dynamics
ASJC Scopus subject areas
- Astronomy and Astrophysics
- Space and Planetary Science