On the nature of the Extremely Red Galaxies
نویسندگان
چکیده
We present a method based on two broad-band colors to investigate the nature of the Extremely Red Objects (EROs), i.e., the galaxies selected to have very red optical-to-infrared colors. Dusty starburst and old ellipticals at redshifts between 1 and 2 appear to occupy two different regions of the J-K vs. I-K color diagram, allowing for an easy classification. This diagnostic was applied to a complete sample of 57 EROs: the two populations are found to be present in the sample in similar abundances. The cosmic star formation density in the dusty starbursts is found to be of the order of that in the Lyman-Break Galaxies (LBG).
منابع مشابه
Pulsating red giant and supergiant stars in the Local Group dwarf galaxy Andromeda I
We have conducted an optical long-term monitoring survey of the majority of dwarf galaxies in the Local Group, with the Isaac Newton Telescope (INT), to identify the long period variable (LPV) stars. LPV stars vary on timescales of months to years, and reach the largest amplitudes of their brightness variations at optical wavelengths, due to the changing temperature. They trace stellar populati...
متن کاملExtremely Red and Dusty Galaxies
Preliminary results of a project aiming at unveiling the nature of the extremely red galaxies (ERGs) 1 found in deep optical-NIR surveys are presented. Very little is known about these objects, the critical issue being whether they are old ellipticals at z>1 or distant star-forming galaxies strongly reddened by dust extinction. We expect to shed light onto the unknown nature of these galaxies b...
متن کاملStellar Populations in the Central Galaxies of Fossil Groups
It is inferred from the symmetrical and luminous X-ray emission of fossil groups that they are mature, relaxed galaxy systems. Cosmological simulations and observations focusing on their dark halo and inter-galactic medium properties confirm their early formation. Recent photometric observations suggest that, unlike the majority of non-fossil brightest group galaxies (BGGs), the central early-t...
متن کاملAGN Zoo and Classications of Active Galaxies
We review the variety of Active Galactic Nuclei (AGN) classes (so-calledAGN zoo") and classification schemes of galaxies by activity types based on their optical emission-line spectrum, as well as other parameters and other than optical wave-length ranges. A historical overview of discoveries of various types of active galaxies is given, including Seyfert galaxies, radio galaxies, QSOs, BL Lace...
متن کاملMassive , red galaxies in a hierarchical universe - I Counts of Extremely Red Objects and basic properties
We present predictions for the abundance and nature of Extremely Red Objects (EROs) in the Λ cold dark matter model. EROs are red, massive galaxies observed at z ≥ 1 and their numbers and properties pose a challenge to hierarchical galaxy formation models. We compare the predictions from two published models, one of which invokes a “superwind” to regulate star formation in massive haloes and th...
متن کامل