Subscribe to the gold package and get unlimited access to Shamra Academy
Register a new userClustering and descendants of MUSYC galaxies at z<1.5
169
0
0.0
(
0
)
Added by
Nelson David Padilla
Publication date
2010
fields
Physics
and research's language is
English
Authors
Nelson Padilla
Ask ChatGPT about the research
No Arabic abstract
We measure the evolution of galaxy clustering out to a redshift of z~1.5 using data from two MUSYC fields, the Extended Hubble Deep Field South (EHDF-S) and the Extended Chandra Deep Field South (ECDF-S). We use photometric redshift information to calculate the projected-angular correlation function, omega(sigma), from which we infer the projected correlation function Xi(sigma). We demonstrate that this technique delivers accurate measurements of clustering even when large redshift measurement errors affect the data. To this aim we use two mock MUSYC fields extracted from a LambdaCDM simulation populated with GALFORM semi-analytic galaxies which allow us to assess the degree of accuracy of our estimates of Xi(sigma) and to identify and correct for systematic effects in our measurements. We study the evolution of clustering for volume limited subsamples of galaxies selected using their photometric redshifts and rest-frame r-band absolute magnitudes. We find that the real-space correlation length r_0 of bright galaxies, M_r<-21 (rest-frame) can be accurately recovered out to z~1.5, particularly for ECDF-S given its near-infrared photometric coverage. There is mild evidence for a luminosity dependent clustering in both fields at the low redshift samples (up to <z>=0.57), where the correlation length is higher for brighter galaxies by up to 1Mpc/h between median rest-frame r-band absolute magnitudes of -18 to -21.5. As a result of the photometric redshift measurement, each galaxy is assigned a best-fit template; we restrict to E and E+20%Sbc types to construct subsamples of early type galaxies (ETGs). Our ETG samples show a strong increase in r_0 as the redshift increases, making it unlikely (95% level) that ETGs at median redshift z_med=1.15 are the direct progenitors of ETGs at z_med=0.37 with equivalent passively evolved luminosities. (ABRIDGED)
rate research
Read More
We present measurements of the spatial clustering of galaxies with stellar masses >10^11Msun, infrared luminosities >10^12 Lsun, and star formation rates >200Msun per year in two redshift intervals; 1.5<z<2.0 and 2<z<3. Both samples cluster very strongly, with spatial correlation lengths of r_0=14.40+/-1.99 h^-1Mpc for the 2<z<3 sample, and r_0=9.40+/-2.24 h^-1Mpc for the 1.5<z<2.0 sample. These clustering amplitudes are consistent with both populations residing in dark matter haloes with masses of ~6x10^13Msun, making them among the most biased galaxies at these epochs. We infer, from this and previous results, that a minimum dark matter halo mass is an important factor for all forms of luminous, obscured activity in galaxies at z>1, both starbursts and AGN. Adopting plausible models for the growth of DM haloes with redshift, then the haloes hosting the 2<z<3 sample will likely host the richest clusters of galaxies at z=0, whereas the haloes hosting the 1.5<z<2.0 sample will likely host poor to rich clusters at z=0. We conclude that ULIRGs at z>1 signpost stellar buildup in galaxies that will reside in clusters at z=0, with ULIRGs at increasing redshifts signposting the buildup of stars in galaxies that will reside in increasingly rich clusters.
We observed star-forming galaxies at z~1.5 selected from the HyperSuprimeCam Subaru Strategic Program. The galaxies are part of two significant overdensities of [OII] emitters identified via narrow-band imaging and photometric redshifts from grizy photometry. We used VLT/KMOS to carry out Halpha integral field spectroscopy of 46 galaxies in total. Ionized gas maps, star formation rates and velocity fields were derived from the Halpha emission line. We quantified morphological and kinematical asymmetries to test for potential gravitational (e.g. galaxy-galaxy) or hydrodynamical (e.g. ram-pressure) interactions. Halpha emission was detected in 36 targets. 34 of the galaxies are members of two (proto-)clusters at z=1.47, confirming our selection strategy to be highly efficient. By fitting model velocity fields to the observed ones, we determined the intrinsic maximum rotation velocity Vmax of 14 galaxies. Utilizing the luminosity-velocity (Tully-Fisher) relation, we find that these galaxies are more luminous than their local counterparts of similar mass by up to ~4 mag in the rest-frame B-band. In contrast to field galaxies at z<1, the offsets of the z~1.5 (proto-)cluster galaxies from the local Tully-Fisher relation are not correlated with their star formation rates but with the ratio between Vmax and gas velocity dispersion sigma_g. This probably reflects that, as is observed in the field at similar redshifts, fewer disks have settled to purely rotational kinematics and high Vmax/sigma_g ratios. Due to relatively low galaxy velocity dispersions (sigma_v < 400 km/s) of the (proto-)clusters, gravitational interactions likely are more efficient, resulting in higher kinematical asymmetries, than in present-day clusters. (abbr.)
We report Herschel SPIRE (250, 350, and 500 micron) detections of 32 quasars with redshifts 0.5 < z < 3.6 from the Herschel Multi-tiered Extragalactic Survey. These sources are from a MIPS 24 micron flux-limited sample of 326 quasars in the Lockman Hole Field. The extensive multi-wavelength data available in the field permit construction of the rest-frame Spectral Energy Distributions (SEDs)from ultraviolet to the mid-infrared for all sources, and to the far-infrared (FIR) for the 32 objects. Most quasars with Herschel FIR detections show dust temperatures in the range of 25K to 60K, with a mean of 34K. The FIR luminosities range from 10^{11.3} to 10^{13.5} Lsun, qualifying most of their hosts as ultra- or hyper-luminous infrared galaxies. These FIR-detected quasars may represent a dust-rich population, but with lower redshifts and fainter luminosities than quasars observed at ~ 1 mm. However, their FIR properties cannot be predicted from shorter wavelengths (0.3--20 micron, rest-frame), and the bolometric luminosities derived using the 5100 A index may be underestimated for these FIR-detected quasars. Regardless of redshift, we observed a decline in the relative strength of FIR luminosities for quasars with higher near-infrared luminosities.
Calculating the galaxy merger rate requires both a census of galaxies identified as merger candidates, and a cosmologically-averaged `observability timescale T_obs(z) for identifying galaxy mergers. While many have counted galaxy mergers using a variety of techniques, T_obs(z) for these techniques have been poorly constrained. We address this problem by calibrating three merger rate estimators with a suite of hydrodynamic merger simulations and three galaxy formation models. We estimate T_obs(z) for (1) close galaxy pairs with a range of projected separations, (2) the morphology indicator G-M20, and (3) the morphology indicator asymmetry A. Then we apply these timescales to the observed merger fractions at z < 1.5 from the recent literature. When our physically-motivated timescales are adopted, the observed galaxy merger rates become largely consistent. The remaining differences between the galaxy merger rates are explained by the differences in the range of mass-ratio measured by different techniques and differing parent galaxy selection. The major merger rate per unit co-moving volume for samples selected with constant number density evolves much more strongly with redshift (~ (1+z)^(+3.0 pm 1.1)) than samples selected with constant stellar mass or passively evolving luminosity (~ (1+z)^(+0.1 pm 0.4)). We calculate the minor merger rate (1:4 < M_{sat}/M_{primary} <~ 1:10) by subtracting the major merger rate from close pairs from the `total merger rate determined by G-M20. The implied minor merger rate is ~3 times the major merger rate at z ~ 0.7, and shows little evolution with redshift.
In this work, we present results for the photometric and clustering properties of galaxies that arise in a LambdaCDM hydrodynamical simulation of the local universe. The present-day distribution of matter was constructed to match the observed large scale pattern of the IRAS 1.2-Jy galaxy survey. Our simulation follows the formation and evolution of galaxies in a cosmological sphere with a volume of ~130^3 (Mpc/h)^3 including supernova feedback, galactic winds, photoheating due to an uniform meta-galactic background and chemical enrichment of the gas and stellar populations. However, we do not consider AGNs. In the simulation, a total of ~20000 galaxies are formed above the resolution limit, and around 60 haloes are more massive than ~10^14 M_sun. Luminosities of the galaxies are calculated based on a stellar population synthesis model including the attenuation by dust, which is calculated from the cold gas left within the simulated galaxies. Environmental effects like colour bi-modality and differential clustering power of the hydrodynamical galaxies are qualitatively similar to observed trends. Nevertheless, the overcooling present in the simulations lead to too blue and overluminous brightest cluster galaxies (BCGs). To overcome this, we mimic the late-time suppression of star formation in massive halos by ignoring recently formed stars with the aid of a simple post-processing recipe. In this way we find luminosity functions, both for field and group/cluster galaxies, in better agreement with observations. Specifically, the BCGs then follow the observed luminosity-halo mass relation. However, in such a case, the colour bi-modality is basically lost, pointing towards a more complex interplay of late suppression of star formation than what is given by the simple scheme adopted.
Log in to be able to interact and post comments
comments
Fetching comments
Sign in to be able to follow your search criteria
