We explore the redshift evolution of a curious correlation between the star formation properties of central galaxies and their satellites (‘galactic conformity’) at intermediate to high redshift (0.4 ...< z < 1.9). Using an extremely deep near-infrared survey, we study the distribution and properties of satellite galaxies with stellar masses, log(M
*/M⊙) > 9.7, around central galaxies at the characteristic Schechter function mass, M ∼ M*. We fit the radial profiles of satellite number densities with simple power laws, finding slopes in the range −1.1 to −1.4 for mass-selected satellites, and −1.3 to −1.6 for passive satellites. We confirm the tendency for passive satellites to be preferentially located around passive central galaxies at 3σ significance and show that it exists to at least z ∼ 2. Meanwhile, the quenched fraction of satellites around star-forming galaxies is consistent with field galaxies of equal stellar masses. We find no convincing evidence for a redshift-dependent evolution of these trends. One simple interpretation of these results is that only passive central galaxies occupy an environment that is capable of independently shutting off star formation in satellite galaxies. By examining the satellites of higher stellar mass star-forming galaxies (log(M
*/M⊙) > 11), we conclude that the origin of galactic conformity is unlikely to be exclusively due to the host dark matter halo mass. A halo-mass-independent correlation could be established by either formation bias or a more physical connection between central and satellite star formation histories. For the latter, we argue that a star formation (or active galactic nucleus) related outburst event from the central galaxy could establish a hot halo environment which is then capable of quenching both central and satellite galaxies.
We investigate galactic-scale outflows in the redshift range 0.71 ≤ z ≤ 1.63, using 413 K-band selected galaxies observed in the spectroscopic follow-up of the UKIDSS Ultra-Deep Survey (UDSz). The ...galaxies have an average stellar mass of ∼109.5 M and span a wide range in rest-frame colours, representing typical star-forming galaxies at this epoch. We stack the spectra by various galaxy properties, including stellar mass, O ii equivalent width, star formation rate, specific star formation rate and rest-frame spectral indices. We find that outflows are present in virtually all spectral stacks, with velocities ranging from 100 to 1000 km s−1, indicating that large-scale outflowing winds are a common property at these redshifts. The highest velocity outflows (>500 km s−1) are found in galaxies with the highest stellar masses and the youngest stellar populations. Our findings suggest that high-velocity galactic outflows are mostly driven by star-forming processes rather than active galactic nuclei, with implied mass outflow rates comparable to the rates of star formation. Such behaviour is consistent with models required to reproduce the high-redshift mass-metallicity relation.
The UKIRT Infrared Deep Sky Survey (UKIDSS) Lawrence, A.; Warren, S. J.; Almaini, O. ...
Monthly notices of the Royal Astronomical Society,
08/2007, Letnik:
379, Številka:
4
Journal Article
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We describe the goals, design, implementation, and initial progress of the UKIRT Infrared Deep Sky Survey (UKIDSS), a seven-year sky survey which began in 2005 May. UKIDSS is being carried out using ...the UKIRT Wide Field Camera (WFCAM), which has the largest étendue of any infrared astronomical instrument to date. It is a portfolio of five survey components covering various combinations of the filter set ZYJHK and H2. The Large Area Survey, the Galactic Clusters Survey, and the Galactic Plane Survey cover approximately 7000 deg2 to a depth of K∼ 18; the Deep Extragalactic Survey covers 35 deg2 to K∼ 21, and the Ultra Deep Survey covers 0.77 deg2 to K∼ 23. Summed together UKIDSS is 12 times larger in effective volume than the 2MASS survey. The prime aim of UKIDSS is to provide a long-term astronomical legacy data base; the design is, however, driven by a series of specific goals – for example, to find the nearest and faintest substellar objects, to discover Population II brown dwarfs, if they exist, to determine the substellar mass function, to break the z= 7 quasar barrier; to determine the epoch of re-ionization, to measure the growth of structure from z= 3 to the present day, to determine the epoch of spheroid formation, and to map the Milky Way through the dust, to several kpc. The survey data are being uniformly processed. Images and catalogues are being made available through a fully queryable user interface – the WFCAM Science Archive (http://surveys.roe.ac.uk/wsa). The data are being released in stages. The data are immediately public to astronomers in all ESO member states, and available to the world after 18 months. Before the formal survey began, UKIRT and the UKIDSS consortia collaborated in obtaining and analysing a series of small science verification (SV) projects to complete the commissioning of the camera. We show some results from these SV projects in order to demonstrate the likely power of the eventual complete survey. Finally, using the data from the First Data Release, we assess how well UKIDSS is meeting its design targets so far.
We present the results of a study of a large sample of luminous (z′AB < 26) Lyman-break galaxies (LBGs) in the redshift interval 4.7 < z < 6.3, selected from a contiguous 0.63 deg2 area covered by ...the UKIRT Infrared Deep Sky Survey Ultra Deep Survey and the Subaru XMM–Newton Survey. Utilizing the large area coverage and the excellent available optical+near-infrared data, we use a photometric redshift analysis to derive a new, robust, measurement of the bright end (L≥L★) of the ultraviolet-selected luminosity function at high redshift. When combined with literature studies of the fainter LBG population, our new sample provides improved constraints on the luminosity function of redshift 5 < z < 6 LBGs over the luminosity range 0.1L★≲L≲ 10L★. A maximum likelihood analysis returns best-fitting Schechter function parameters of M★1500=−20.73 ± 0.11, φ★= 0.0009 ± 0.0002 Mpc−3 and α=−1.66 ± 0.06 for the luminosity function at z= 5, and M★1500=−20.04 ± 0.12, φ★= 0.0018 ± 0.0005 Mpc−3 and α=−1.71 ± 0.11 at z= 6. In addition, an analysis of the angular clustering properties of our LBG sample demonstrates that luminous 5 < z < 6 LBGs are strongly clustered (r0= 8.1+2.1−1.5h−170 Mpc), and consistent with the occupation of dark matter haloes with masses of ≃1011.5−12 M⊙. Moreover, by stacking the available multiwavelength imaging data for the high-redshift LBGs, it is possible to place useful constraints on their typical stellar mass. The results of this analysis suggest that luminous LBGs at 5 < z < 6 have an average stellar mass of log10(M/M⊙) = 10.0+0.2−0.4, consistent with the results of the clustering analysis assuming plausible values for the ratio of stellar to dark matter. Finally, by combining our luminosity function results with those of the stacking analysis we derive estimates of ≃1 × 107 and ≃4 × 106 M⊙ Mpc−3 for the stellar mass density at z≃ 5 and 6, respectively.
We present the Spitzer Extragalactic Representative Volume Survey (SERVS), an18 deg2
18
deg
2
medium-deep survey at 3.6 and 4.5 μm with the postcryogenicSpitzer Space Telescopeto≈2 μJy
≈
2
μ
...Jy
(AB = 23.1
AB
=
23.1
) depth of five highly observed astronomical fields (ELAIS-N1, ELAIS-S1, Lockman Hole, Chandra Deep Field South, and XMM-LSS). SERVS is designed to enable the study of galaxy evolution as a function of environment from
z ∼ 5
z
∼
5
to the present day and is the first extragalactic survey that is both large enough and deep enough to put rare objects such as luminous quasars and galaxy clusters at
z ≳ 1
z
≳
1
into their cosmological context. SERVS is designed to overlap with several key surveys at optical, near- through far-infrared, submillimeter, and radio wavelengths to provide an unprecedented view of the formation and evolution of massive galaxies. In this article, we discuss the SERVS survey design, the data processing flow from image reduction and mosaicking to catalogs, and coverage of ancillary data from other surveys in the SERVS fields. We also highlight a variety of early science results from the survey.
Observations of distant supernovae indicate that the Universe is now in a phase of accelerated expansion the physical cause of which is a mystery. Formally, this requires the inclusion of a term ...acting as a negative pressure in the equations of cosmic expansion, accounting for about 75 per cent of the total energy density in the Universe. The simplest option for this 'dark energy' corresponds to a 'cosmological constant', perhaps related to the quantum vacuum energy. Physically viable alternatives invoke either the presence of a scalar field with an evolving equation of state, or extensions of general relativity involving higher-order curvature terms or extra dimensions. Although they produce similar expansion rates, different models predict measurable differences in the growth rate of large-scale structure with cosmic time. A fingerprint of this growth is provided by coherent galaxy motions, which introduce a radial anisotropy in the clustering pattern reconstructed by galaxy redshift surveys. Here we report a measurement of this effect at a redshift of 0.8. Using a new survey of more than 10,000 faint galaxies, we measure the anisotropy parameter = 0.70 ± 0.26, which corresponds to a growth rate of structure at that time of f = 0.91 ± 0.36. This is consistent with the standard cosmological-constant model with low matter density and flat geometry, although the error bars are still too large to distinguish among alternative origins for the accelerated expansion. The correct origin could be determined with a further factor-of-ten increase in the sampled volume at similar redshift.
We use the United Kingdom Infrared Telescope Deep Sky Survey (UKIDSS) Ultra Deep Survey (UDS), the deepest degree-scale near-infrared survey to date, to investigate the clustering of star-forming and ...passive galaxies to z ∼ 3.5. Our new measurements include the first determination of the clustering for passive galaxies at z > 2, which we achieve using a cross-correlation technique. We find that passive galaxies are the most strongly clustered, typically hosted by massive dark matter haloes with M
halo > 5 × 1012 M irrespective of redshift or stellar mass. Our findings are consistent with models in which a critical halo mass determines the transition from star-forming to passive galaxies. Star-forming galaxies show no strong correlation between stellar mass and halo mass, but passive galaxies show evidence for an anticorrelation; low-mass passive galaxies appear, on average, to be located in the most massive haloes. These results can be understood if the termination of star formation is most efficient for galaxies of low stellar mass in very dense environments.
The galaxy cluster CLG0218.3-0510 at z = 1.62 is one of the most distant galaxy clusters known, with a rich multiwavelength data set that confirms a mature galaxy population already in place. Using ...very deep, wide-area (20 Mpc × 20 Mpc) imaging by Spitzer MIPS at 24 μm, in conjunction with Herschel five-band imaging from 100 to 500 μm, we investigate the dust-obscured, star formation properties in the cluster and its associated large-scale environment. Our galaxy sample of 693 galaxies at z ∼ 1.62 detected at 24 μm (10 spectroscopic and 683 photo-z) includes both cluster galaxies (i.e. within r < 1 Mpc projected cluster-centric radius) and field galaxies, defined as the region beyond a radius of 3 Mpc. The star formation rates (SFRs) derived from the measured infrared luminosity range from 18 to 2500 M yr−1, with a median of 55 M yr−1, over the entire radial range (10 Mpc). The cluster's brightest far-infrared galaxy, taken as the centre of the galaxy system, is vigorously forming stars at a rate of 256 ± 70 M yr−1, and the total cluster SFR enclosed in a circle of 1 Mpc is 1161 ± 96 M yr−1. We estimate a dust extinction of ∼3 mag by comparing the SFRs derived from O ii luminosity with the ones computed from the 24 μm fluxes. We find that the in-falling region (1-3 Mpc) is special: there is a significant decrement (3.5×) of passive relative to star-forming galaxies in this region, and the total SFR of the galaxies located in this region is lower (∼130 M yr−1 Mpc−2) than anywhere in the cluster or field, regardless of their stellar mass. In a complementary approach, we compute the local galaxy density, Σ5, and find no trend between SFR and Σ5. However, we measure an excess of star-forming galaxies in the cluster relative to the field by a factor of 1.7, that lends support to a reversal of SF-density relation in CLG0218.
We report the results of a comprehensive study of the relationship between galaxy size, stellar mass and specific star formation rate (sSFR) at redshifts 1.3 < z < 1.5. Based on a mass-complete (M
≥ ...6 × 1010 M), spectroscopic sample from the UK Infrared Deep Sky Survey (UKIDSS) Ultradeep Survey, with accurate stellar-mass measurements derived from spectro-photometric fitting, we find that at z 1.4 the location of massive galaxies on the size-mass plane is determined primarily by their sSFR. At this epoch, we find that massive galaxies which are passive (sSFR ≤ 0.1 Gyr−1) follow a tight size-mass relation, with half-light radii a factor of f
g = 2.4 ± 0.2 smaller than their local counterparts. Moreover, amongst the passive sub-sample we find no evidence that the off-set from the local size-mass relation is a function of stellar population age. In contrast, we find that massive star-forming galaxies at this epoch lie closer to the local late-type size-mass relation and are only a factor of f
g = 1.6 ± 0.2 smaller than observed locally. Based on a sub-sample with dynamical-mass estimates, which consists of both passive and star-forming objects, we also derive an independent estimate of f
g = 2.3 ± 0.3 for the typical growth in half-light radius between z 1.4 and the present day. Focusing on the passive sub-sample, we conclude that to produce the necessary evolution predominantly via major mergers would require an unfeasible number of merger events and overpopulate the high-mass end of the local stellar-mass function. In contrast, we find that a scenario in which mass accretion is dominated by minor mergers can comfortably produce the necessary evolution, whereby an increase in stellar mass of only a factor of 2, accompanied by size growth of a factor of 3.5, is required to reconcile the size-mass relation at z 1.4 with that observed locally. Finally, we note that a significant fraction (44 ± 12 per cent) of the passive galaxies in our sample have a disc-like morphology, providing additional evidence that separate physical processes are responsible for the quenching of star formation and morphological transformation in massive galaxies.
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