Subscribe to the gold package and get unlimited access to Shamra Academy
Register a new userHyper Extremely Red Objects in the Subaru Deep Field: Evidence for Primordial Elliptical Galaxies in the Dusty Starburst Phase
39
0
0.0
(
0
)
Authors
Tomonori Totani
Ask ChatGPT about the research
No Arabic abstract
We report observational analyses and theoretical interpretations of unusually red galaxies in the Subaru Deep Field (SDF). A careful analysis of the SDF data revealed a population with unusually red near-infrared (NIR) colors of J - K >~ 3-4, with higher confidence than the previous SDF result. Their surface number density drastically increases at K >~ 22 and becomes roughly the same with that of dusty starburst galaxies detected by submillimeter observations in recent years. These colors are even redder than the known population of the extremely red objects (EROs), and too red to explain by passively evolving elliptical galaxies which are the largest population of EROs. Hence these hyper extremely red objects (HEROs) should be considered as a distinct population from EROs. We discuss several possible interpretations of these enigmatic objects, and we show that these red NIR colors, K-band and sub-mm flux, and surface number density are quantitatively best explained by primordial elliptical galaxies reddened by dust, still in the starburst phase of their formation at z ~ 3.
rate research
Read More
We have mapped the submillimetre wavelength continuum emission from the Subaru Deep Field (SDF) at 450 and 850 microns with the Submillimetre Common-User Bolometer Array (SCUBA) detector on the James Clerk Maxwell Telescope (JCMT). The near-IR image of the SDF is one of the deepest near-IR images available and contains four `hyper extremely red objects (HEROs). These data allow us to test the connection between `extremely red objects (EROs) found in IR surveys and the population of bright submillimetre sources found with SCUBA. We present a weak measurement of the average flux of the four K-band selected HEROs of 1.15 (+/-0.46) mJy, which fails to support the hypothesis that HEROs should be bright SCUBA sources. Our data are consistent with the HEROs being objects with SEDs like that of Arp220 out to z~1.7, however, the extinction in the HEROs must be about 1 magnitude greater in the J-band than is the case for Arp220 and they would need to be 1.7 times as luminous as Arp220. On the other hand, an evolutionary model of elliptical galaxies at z~2-3 in a dusty starburst phase is also in agreement with the submillimetre data, as was originally proposed for the HEROs.
We present Spitzer Space Telescope observations of the well-studied extremely red objects (EROs) HR10 and LBDS53W091 from 3.6 to 160 microns. These galaxies are the prototypes of the two primary classes of EROs: dusty starbursts and old, evolved galaxies, respectively. Both galaxies, as well as LBDS53W069, another example of an old, quiescent galaxy, are well-detected out to 8 microns. However, only the dusty starburst HR10 is detected in the far-infrared. All three EROs have stellar masses of a few times 10^11 M(sun). Using evolutionary model fits to their multiband photometry, we predict the infrared colors of similar EROs at 1<z<2. We find that blueward of observed 10 microns, the two ERO classes are virtually indistinguishable photometrically. Deep spectroscopy and 24 micron data allow the classes to be separated.
We present a study of the classification of z ~1 extremely red objects (EROs), using a combination of HST/ACS, Spitzer/IRAC, and ground-based images of the COSMOS field. Our sample includes about 5300 EROs with i-Ks>2.45 (AB, equivalently I-Ks=4 in Vega) and Ks<=21.1 (AB). For EROs in our sample, we compute, using the ACS F814W images, their concentration, asymmetry, as well as their Gini coefficient and the second moment of the brightest 20% of their light. Using those morphology parameters and the Spitzer/IRAC [3.6]-[8.0] color, the spectral energy distribution (SED) fitting method, we classify EROs into two classes: old galaxies (OGs) and young, dusty starburst galaxies (DGs). We found that the fraction of OGs and DGs in our sample is similar, about 48 percentages of EROs in our sample are OGs, and 52 percentages of them are DGs. To reduce the redundancy of these three different classification methods, we performed a principal component analysis on the measurements of EROs, and find that morphology parameters and SEDs are efficient in segregating OGs and DGs. The [3.6]-[8.0] color, which depends on reddening, redshift, and photometric accuracy, is difficult to separate EROs around the discriminating line between starburst and elliptical. We investigate the dependence of the fraction of EROs on their observational properties, and the results suggest that DGs become increasingly important at fainter magnitudes, redder colors, and higher redshifts.
The Phoenix Deep Survey (PDS) is a multiwavelength survey based on deep 1.4 GHz radio observations used to identify a large sample of star forming galaxies to z=1. Here we present an exploration of the evolutionary constraints on the star-forming population imposed by the 1.4 GHz source counts, followed by an analysis of the average properties of extremely red galaxies in the PDS, by using the stacking technique.
We investigate Extremely Red Objects (EROs) using near- and mid-infrared observations in five passbands (3.6 to 24 micron) obtained from the Spitzer Space Telescope, and deep ground-based R and K imaging. The great sensitivity of the IRAC camera allows us to detect 64 EROs in only 12 minutes of IRAC exposure time, by means of an R-[3.6] color cut (analogous to the traditional red R-K cut). A pure infrared K-[3.6] red cut detects a somewhat different population and may be more effective at selecting z > 1.3 EROs. We find 17% of all galaxies detected by IRAC at 3.6 or 4.5 micron to be EROs. These percentages rise to about 40% at 5.8 micron, and about 60% at 8.0 micron. We utilize the spectral bump at 1.6 micron to divide the EROs into broad redshift slices using only near-infrared colors (2.2/3.6/4.5 micron). We conclude that two-thirds of all EROs lie at redshift z > 1.3. Detections at 24 micron imply that at least 11% of 0.6 < z < 1.3 EROs and at least 22% of z > 1.3 EROs are dusty star-forming galaxies.
Log in to be able to interact and post comments
comments
Fetching comments
Sign in to be able to follow your search criteria
