Now that Atacama Large (Sub)Millimeter Array is reaching its full capabilities, observations of sub-mm emission line deep fields become feasible. We couple a semi-analytic model of galaxy formation ...with a radiative transfer code to make predictions for the luminosity function of CO J =1–0 out to CO J = 6–5 and C ii at redshifts z= 0–6. We find that (1) our model correctly reproduces the CO and C ii emission of low- and high-redshift galaxies and reproduces the available constraints on the CO luminosity function at z ≤ 2.75; (2) we find that the CO and C ii luminosity functions of galaxies increase from z = 6 to z = 4, remain relatively constant till z = 1 and rapidly decrease towards z = 0. The galaxies that are brightest in CO and C ii are found at z ∼ 2; (3) the CO J = 3–2 emission line is most favourable to study the CO luminosity and global H2 mass content of galaxies, because of its brightness and observability with currently available sub-mm and radio instruments; (4) the luminosity functions of high-J CO lines show stronger evolution than the luminosity functions of low-J CO lines; (5) our model barely reproduces the available constraints on the CO and C ii luminosity function of galaxies at z ≥ 1.5 and the CO luminosity of individual galaxies at intermediate redshifts. We argue that this is driven by a lack of cold gas in galaxies at intermediate redshifts as predicted by cosmological simulations of galaxy formation.
Context. Friends-of-friends algorithms are a common tool to detect galaxy groups and clusters in large survey data. In order to be as precise as possible, they have to be carefully calibrated using ...mock catalogues. Aims. We create an accurate and robust description of the matter distribution in the local Universe using the most up-to-date available data. This will provide the input for a specific cosmological test planned as follow-up to this work, and will be useful for general extragalactic and cosmological research. Methods. We created a set of galaxy group catalogues based on the 2MRS and SDSS DR12 galaxy samples using a friends-of-friends based group finder algorithm. The algorithm was carefully calibrated and optimised on a new set of wide-angle mock catalogues from the Millennium simulation, in order to provide accurate total mass estimates of the galaxy groups taking into account the relevant observational biases in 2MRS and SDSS. Results. We provide four different catalogues: (i) a 2MRS based group catalogue; (ii) an SDSS DR12 based group catalogue reaching out to a redshift z = 0.11 with stellar mass estimates for 70% of the galaxies; (iii) a catalogue providing additional fundamental plane distances for all groups of the SDSS catalogue that host elliptical galaxies; (iv) a catalogue of the mass distribution in the local Universe based on a combination of our 2MRS and SDSS catalogues. Conclusions. While motivated by a specific cosmological test, three of the four catalogues that we produced are well suited to act as reference databases for a variety of extragalactic and cosmological science cases. Our catalogue of fundamental plane distances for SDSS groups provides further added value to this paper.
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We present ALMA detections of the CI 1–0, CO J = 3–2, and CO J = 4–3 emission lines, as well as the ALMA band 4 continuum for a compact star-forming galaxy (cSFG) at z = 2.225, 3D-HST GS30274. As is ...typical for cSFGs, this galaxy has a stellar mass of 1.89 ± 0.47 × 1011M⊙, with a star formation rate (SFR) of 214 ± 44 M⊙ yr-1 putting it on the star-forming “main-sequence”, but with an H-band effective radius of 2.5 kpc, making it much smaller than the bulk of “main-sequence” star-forming galaxies. The intensity ratio of the line detections yield an ISM density (~ 6 × 104 cm-3) and a UV-radiation field (~ 2 × 104G0), similar to the values in local starburst and ultra-luminous infrared galaxy environments. A starburst phase is consistent with the short depletion times (tH2,dep ≤ 140 Myr) we find in 3D-HST GS30274 using three different proxies for the H2 mass (CI, CO, dust mass). This depletion time is significantly shorter than in more extended SFGs with similar stellar masses and SFRs. Moreover, the gas fraction of 3D-HST GS30274 is smaller than typically found in extended galaxies. We measure the CO and CI kinematics and find a FWHM line width of ~ 750 ± 41 km s-1. The CO and CI FWHM are consistent with a previously measured Hα FWHM for this source. The line widths are consistent with gravitational motions, suggesting we are seeing a compact molecular gas reservoir. A previous merger event, as suggested by the asymmetric light profile, may be responsible for the compact distribution of gas and has triggered a central starburst event. This event gives rise to the starburst-like ISM properties and short depletion times in 3D-HST GS30274. The centrally located and efficient star formation is quickly building up a dense core of stars, responsible for the compact distribution of stellar light in 3D-HST GS30274.
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Based on data from the Galaxy and Mass Assembly (GAMA) survey, we report on the discovery of structures that we refer to as 'tendrils' of galaxies: coherent, thin chains of galaxies that are rooted ...in filaments and terminate in neighbouring filaments or voids. On average, tendrils contain six galaxies and span 10 h
−1 Mpc. We use the so-called line correlation function to prove that tendrils represent real structures rather than accidental alignments. We show that voids found in the Sloan Digital Sky Survey, 7th data release survey that overlap with GAMA regions contain a large number of galaxies, primarily belonging to tendrils. This implies that void sizes are strongly dependent on the number density and sensitivity limits of a survey. We caution that galaxies in low-density regions, which may be defined as 'void galaxies,' will have local galaxy number densities that depend on such observational limits and are likely higher than those can be directly measured.
Context. Backreactions from large-scale inhomogeneities may provide an elegant explanation for the observed accelerated expansion of the universe without the need to introduce dark energy. Aims. We ...propose a cosmological test for a specific model of inhomogeneous cosmology, called timescape cosmology. Using large-scale galaxy surveys such as SDSS and 2MRS, we test the variation of expansion expected in the Λ-cold dark matter (Λ-CDM) model versus a more generic differential expansion using our own calibrations of bounds suggested by timescape cosmology. Methods. Our test measures the systematic variations of the Hubble flow towards distant galaxies groups as a function of the matter distribution in the lines of sight to those galaxy groups. We compare the observed systematic variation of the Hubble flow to mock catalogues from the Millennium Simulation in the case of the Λ-CDM model, and a deformed version of the same simulation that exhibits more pronounced differential expansion. Results. We perform a series of statistical tests, ranging from linear regressions to Kolmogorov-Smirnov tests, on the obtained data. They consistently yield results preferring Λ-CDM cosmology over our approximated model of timescape cosmology. Conclusions. Our analysis of observational data shows no evidence that the variation of expansion differs from that of the standard Λ-CDM model.
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ABSTRACT
We have measured the angular autocorrelation function of near-infrared galaxies in SERVS + DeepDrill, the Spitzer Extragalactic Representative Volume Survey and its follow-up survey of the ...Deep Drilling Fields, in three large fields totalling over 20 deg2 on the sky, observed in two bands centred on 3.6 and 4.5 μm. We performed this analysis on the full sample as well as on sources selected by 3.6–4.5 colour in order to probe clustering for different redshift regimes. We estimated the spatial correlation strength as well, using the redshift distribution from S-COSMOS with the same source selection. The strongest clustering was found for our bluest subsample, with 〈z〉 ∼ 0.7, which has the narrowest redshift distribution of all our subsamples. We compare these estimates to previous results from the literature, but also to estimates derived from mock samples, selected in the same way as the observational data, using deep light-cones generated from the SHARK semi-analytical model of galaxy formation. For all simulated (sub)samples, we find a slightly steeper slope than for the corresponding observed ones, but the spatial clustering length is comparable in most cases.
ABSTRACT
We calculate H α-based star formation rates and determine the star formation rate–stellar mass relation for members of three Spitzer Adaptation of the Red-Sequence Cluster Survey (SpARCS) ...clusters at z ∼ 1.6 and serendipitously identified field galaxies at similar redshifts to the clusters. We find similar star formation rates in cluster and field galaxies throughout our range of stellar masses. The results are comparable to those seen in other clusters at similar redshifts, and consistent with our previous photometric evidence for little quenching activity in clusters. One possible explanation for our results is that galaxies in our z ∼ 1.6 clusters have been accreted too recently to show signs of environmental quenching. It is also possible that the clusters are not yet dynamically mature enough to produce important environmental quenching effects shown to be important at low redshift, such as ram-pressure stripping or harassment.
We present ALMA detections of the CI 1‐0, CO J = 3‐2, and CO J = 4‐3 emission lines, as well as the ALMA band 4 continuum for a compact star‐forming galaxy (cSFG) at z = 2.225, 3D‐HST GS30274. As is ...typical for cSFGs, this galaxy has a stellar mass of 1.89 +/‐ 0.47 x 10(11) M‐circle dot, with a star formation rate (SFR) of 214 +/‐ 44 M‐circle dot yr(‐1) putting it on the star‐forming ``main‐sequence'', but with an H‐band effective radius of 2.5 kpc, making it much smaller than the bulk of ``main‐sequence'' star‐forming galaxies. The intensity ratio of the line detections yield an ISM density (similar to 6 x 10(4) cm(‐3)) and a UV‐radiation field (similar to 2 x 10(4) G(0)), similar to the values in local starburst and ultra‐luminous infrared galaxy environments. A starburst phase is consistent with the short depletion times (t(H2,dep) <= 140 Myr) we find in 3D‐HST GS30274 using three different proxies for the H‐2 mass (CI, CO, dust mass). This depletion time is significantly shorter than in more extended SFGs with similar stellar masses and SFRs. Moreover, the gas fraction of 3D‐HST GS30274 is smaller than typically found in extended galaxies. We measure the CO and CI kinematics and find a FWHM line width of similar to 750 +/‐ 41 km s(‐1). The CO and CI FWHM are consistent with a previously measured H alpha FWHM for this source. The line widths are consistent with gravitational motions, suggesting we are seeing a compact molecular gas reservoir. A previous merger event, as suggested by the asymmetric light profile, may be responsible for the compact distribution of gas and has triggered a central starburst event. This event gives rise to the starburst‐like ISM properties and short depletion times in 3D‐HST GS30274. The centrally located and efficient star formation is quickly building up a dense core of stars, responsible for the compact distribution of stellar light in 3D‐HST GS30274.
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From a volume-limited sample of 45 542 galaxies and 6000 groups with z ≤ 0.213, we use an adapted minimal spanning tree algorithm to identify and classify large-scale structures within the Galaxy And ...Mass Assembly (GAMA) survey. Using galaxy groups, we identify 643 filaments across the three equatorial GAMA fields that span up to 200 h
−1 Mpc in length, each with an average of eight groups within them. By analysing galaxies not belonging to groups, we identify a secondary population of smaller coherent structures composed entirely of galaxies, dubbed 'tendrils' that appear to link filaments together, or penetrate into voids, generally measuring around 10 h
−1 Mpc in length and containing on average six galaxies. Finally, we are also able to identify a population of isolated void galaxies. By running this algorithm on GAMA mock galaxy catalogues, we compare the characteristics of large-scale structure between observed and mock data, finding that mock filaments reproduce observed ones extremely well. This provides a probe of higher order distribution statistics not captured by the popularly used two-point correlation function.
Abstract
Using a sample of 472 local Universe (z < 0.06) galaxies in the stellar mass range $10.25\,\,{<}\,\,\log \boldsymbol {\mathcal {M}}_{\star }/\boldsymbol {\mathcal {M}}_{{\odot }}\,\,{<}\,\, ...10.75$, we explore the variation in galaxy structure as a function of morphology and galaxy colour. Our sample of galaxies is subdivided into red, green, and blue colour groups and into elliptical and non-elliptical (disk-type) morphologies. Using Kilo-Degree Survey (KiDS) and Visible and Infrared Survey Telescope for Astronomy (VISTA) Kilo-Degree Infrared Galaxy Survey (VIKING) derived postage stamp images, a group of eight volunteers visually classified bars, rings, morphological lenses, tidal streams, shells, and signs of merger activity for all systems. We find a significant surplus of rings (2.3σ) and lenses (2.9σ) in disk-type galaxies as they transition across the green valley. Combined, this implies a joint ring/lens green valley surplus significance of 3.3σ relative to equivalent disk-types within either the blue cloud or the red sequence. We recover a bar fraction of ${\sim }44\hbox{ per cent}$ which remains flat with colour, however, we find that the presence of a bar acts to modulate the incidence of rings and (to a lesser extent) lenses, with rings in barred disk-type galaxies more common by ∼20–30 percentage points relative to their unbarred counterparts, regardless of colour. Additionally, green valley disk-type galaxies with a bar exhibit a significant 3.0σ surplus of lenses relative to their blue/red analogues. The existence of such structures rules out violent transformative events as the primary end-of-life evolutionary mechanism, with a more passive scenario the favoured candidate for the majority of galaxies rapidly transitioning across the green valley.
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