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Bright galaxies at submillimetre wavelengths from Herschel are now well known to be predominantly strongly gravitationally lensed. The same models that successfully predicted this strongly lensed population also predict about 1 per cent of faint 450 μm-selected galaxies from deep James Clerk Maxwell Telescope (JCMT) surveys will also be strongly lensed. Follow-up ALMA campaigns have so far found one potential lens candidate, but without clear compelling evidence, for example, from lensing arcs. Here, we report the discovery of a compelling gravitational lens system confirming the lensing population predictions, with a z s = 3.4 ± 0.4 submm source lensed by a z spec = 0.360 foreground galaxy within the COSMOS field, identified through public JWST imaging of a 450 μm source in the SCUBA-2 Ultra Deep Imaging EAO Survey (STUDIES) catalogue. These systems will typically be well within the detectable range of future wide-field surveys such as Euclid and Roman , and since submillimetre galaxies are predominantly very red at optical/near-infrared wavelengths, they will tend to appear in near-infrared channels only. Extrapolating to the Euclid -Wide survey, we predict tens of thousands of strongly lensed near-infrared galaxies. This will be transformative for the study of dusty star-forming galaxies at cosmic noon, but will be a contaminant population in searches for strongly lensed ultra-high-redshift galaxies in Euclid and Roman. [ABSTRACT FROM AUTHOR]

Using a sample of >200 clusters, each with typically 100–200 spectroscopically confirmed cluster members, we search for a signal of alignment between the position angle (PA) of the Brightest Cluster Galaxy (BCG) and the distribution of cluster members on the sky about the cluster centre out to projected distances of 3  R 200. The deep spectroscopy, combined with corrections for spectroscopic incompleteness, makes our sample ideal to determine alignment signal strengths. We also use an SDSS based skeleton of the filamentary large-scale structure (LSS), and measure BCG alignment with the location of the LSS skeleton segments on the sky out to projected distances of 10  R 200. The alignment signal is measured using three separate statistical measures; Rao's spacing test (U), Kuiper's V parameter (V), and the Binomial probability test (P). The significance of the BCG alignment signal with both cluster members and LSS segments is extremely high (1 in a million chance or less to be drawn randomly from a uniform distribution). We investigate a wide set of parameters that may influence the strength of the alignment signal. Clusters with more elliptical-shaped BCGs show stronger alignment with both their cluster members and LSS segments. Also, selecting clusters with closely connected filaments, or using a luminosity-weighted LSS skeleton, increases the alignment signal significantly. Alignment strength decreases with increasing projected distance. Combined, these results provide strong evidence for the growth of clusters and their BCGs by preferential feeding along the direction of the filaments in which they are embedded. [ABSTRACT FROM AUTHOR]

Using a sample of >200 clusters, each with typically 100–200 spectroscopically confirmed cluster members, we search for a signal of alignment between the position angle (PA) of the Brightest Cluster Galaxy (BCG) and the distribution of cluster members on the sky about the cluster centre out to projected distances of 3  R 200. The deep spectroscopy, combined with corrections for spectroscopic incompleteness, makes our sample ideal to determine alignment signal strengths. We also use an SDSS based skeleton of the filamentary large-scale structure (LSS), and measure BCG alignment with the location of the LSS skeleton segments on the sky out to projected distances of 10  R 200. The alignment signal is measured using three separate statistical measures; Rao's spacing test (U), Kuiper's V parameter (V), and the Binomial probability test (P). The significance of the BCG alignment signal with both cluster members and LSS segments is extremely high (1 in a million chance or less to be drawn randomly from a uniform distribution). We investigate a wide set of parameters that may influence the strength of the alignment signal. Clusters with more elliptical-shaped BCGs show stronger alignment with both their cluster members and LSS segments. Also, selecting clusters with closely connected filaments, or using a luminosity-weighted LSS skeleton, increases the alignment signal significantly. Alignment strength decreases with increasing projected distance. Combined, these results provide strong evidence for the growth of clusters and their BCGs by preferential feeding along the direction of the filaments in which they are embedded. [ABSTRACT FROM AUTHOR]

We study the cold gas and dust properties for a sample of red star-forming galaxies called 'red misfits.' We collect single-dish CO observations and H  i observations from representative samples of low-redshift galaxies, as well as our own James Clerk Maxwell Telescope CO observations of red misfits. We also obtain SCUBA-2 850 |$\mu$| m observations for a subset of these galaxies. With these data we compare the molecular gas, total cold gas, and dust properties of red misfits against those of their blue counterparts ('blue actives') taking non-detections into account using a survival analysis technique. We compare these properties at fixed position in the log SFR–log  M ⋆ plane, as well as versus offset from the star-forming main sequence. Compared to blue actives, red misfits have slightly longer molecular gas depletion times, similar total gas depletion times, significantly lower molecular- and total-gas mass fractions, lower dust-to-stellar mass ratios, similar dust-to-gas ratios, and a significantly flatter slope in the log  M mol–log  M ⋆ plane. Our results suggest that red misfits as a population are likely quenching due to a shortage in gas supply. [ABSTRACT FROM AUTHOR]

We present the multiwavelength counterparts of 850- |$\mu$| m selected submillimetre sources over a 2-deg2 field centred on the North Ecliptic Pole. In order to overcome the large beam size (15 arcsec) of the 850- |$\mu$| m images, deep optical to near-infrared (NIR) photometric data and arcsecond-resolution 20-cm images are used to identify counterparts of submillimetre sources. Among 647 sources, we identify 514 reliable counterparts for 449 sources (69 per cent in number), based either on probabilities of chance associations calculated from positional offsets or offsets combined with the optical-to-NIR colours. In the radio imaging, the fraction of 850- |$\mu$| m sources having multiple counterparts is 7 per cent. The photometric redshift, infrared luminosity, stellar mass, star formation rate (SFR), and the active galactic nucleus (AGN) contribution to the total infrared luminosity of the identified counterparts are investigated through spectral energy distribution fitting. The SMGs are infrared-luminous galaxies at an average 〈 z 〉 = 2.5 with log10(L IR/L⊙) = 11.5–13.5, with a mean stellar mass of log10(M star/M⊙) = 10.90 and SFR of |$\mathrm{log}_{10} (\mathrm{SFR/M_\odot \, yr^{-1}})=2.34$|⁠. The submillimetre galaxies (SMGs) show twice as large SFR as galaxies on the star-forming main sequence, and about 40 per cent of the SMGs are classified as objects with bursty star formation. At z ≥ 4, the contribution of AGN luminosity to total luminosity for most SMGs is larger than 30 per cent. The FIR-to-radio correlation coefficient of SMGs is consistent with that of main-sequence galaxies at z ≃ 2. [ABSTRACT FROM AUTHOR]

We study the galaxy merger fraction and its dependence on star formation mode in the 5.4 deg2 of the North Ecliptic Pole-Wide Field. We select 6352 galaxies with AKARI 9  |$\mu$| m detections, and identify mergers among them using the Gini coefficient and M 20 derived from the Subaru/Hyper Suprime-Cam (HSC) optical images. We obtain the total infrared luminosity and star formation rate of galaxies using the spectral energy distribution templates based on one band, AKARI |$9\, \mu$| m. We classify galaxies into three different star formation modes (i.e. starbursts, main-sequence, and quiescent galaxies) and calculate the merger fractions for each. We find that the merger fractions of galaxies increase with redshift at z < 0.6. The merger fractions of starbursts are higher than those of main-sequence and quiescent galaxies in all redshift bins. We also examine the merger fractions of far-infrared-detected galaxies that have at least one detection from Herschel /Spectral and Photometric Imaging Receiver (SPIRE). We find that Herschel -detected galaxies have higher merger fraction compared to non- Herschel -detected galaxies, and both Herschel -detected and non- Herschel -detected galaxies show clearly different merger fractions depending on the star formation modes. [ABSTRACT FROM AUTHOR]

How does the environment affect active galactic nucleus (AGN) activity? We investigated this question in an extinction-free way by selecting 1120 infrared (IR) galaxies in the AKARI North Ecliptic Pole Wide field at redshift z ≤ 1.2. A unique feature of the AKARI satellite is its continuous nine-band IR filter coverage, providing us with an unprecedentedly large sample of IR spectral energy distributions (SEDs) of galaxies. By taking advantage of this, for the first time, we explored the AGN activity derived from SED modelling as a function of redshift, luminosity, and environment. We quantified AGN activity in two ways: AGN contribution fraction (ratio of AGN luminosity to the total IR luminosity), and AGN number fraction (ratio of number of AGNs to the total galaxy sample). We found that galaxy environment (normalized local density) does not greatly affect either definitions of AGN activity of our IRG/LIRG samples (log L TIR ≤ 12). However, we found a different behaviour for ULIRGs (log L TIR > 12). At our highest redshift bin (0.7 ≲ z ≲ 1.2), AGN activity increases with denser environments, but at the intermediate redshift bin (0.3 ≲ z ≲ 0.7), the opposite is observed. These results may hint at a different physical mechanism for ULIRGs. The trends are not statistically significant (p ≥ 0.060 at the intermediate redshift bin, and p ≥ 0.139 at the highest redshift bin). Possible different behaviour of ULIRGs is a key direction to explore further with future space missions (e.g. JWST, Euclid, SPHEREx). [ABSTRACT FROM AUTHOR]

To study environmental effects on the circumgalactic medium (CGM), we use the samples of redMaPPer galaxy clusters, background quasars, and cluster galaxies from the Sloan Digital Sky Survey (SDSS). With ∼82 000 quasar spectra, we detect 197 Mg  ii absorbers in and around the clusters. The detection rate per quasar is 2.7 ± 0.7 times higher inside the clusters than outside the clusters, indicating that Mg  ii absorbers are relatively abundant in clusters. However, when considering the galaxy number density, the absorber-to-galaxy ratio is rather low inside the clusters. If we assume that Mg  ii absorbers are mainly contributed by the CGM of massive star-forming galaxies, a typical halo size of cluster galaxies is smaller than that of field galaxies by 30 ± 10 per cent. This finding supports that galaxy haloes can be truncated by interaction with the host cluster. [ABSTRACT FROM AUTHOR]

The AKARI space infrared telescope has performed near-infrared to mid-infrared (MIR) observations on the North Ecliptic Pole Wide (NEPW) field (5.4 deg2) for about 1 yr. AKARI took advantage of its continuous nine photometric bands, compared with NASA's Spitzer and Wide-field Infrared Survey Explorer (WISE) space telescopes, which had only four filters with a wide gap in the MIR. The AKARI NEPW field lacked deep and homogeneous optical data, limiting the use of nearly half of the IR sources for extragalactic studies, because of the absence of photometric redshift (photo -z). To remedy this, we have recently obtained deep optical imaging over the NEPW field with five bands (g, r, i, z and Y) of the Hyper Suprime-Camera (HSC) on the Subaru 8-m telescope. We optically identify AKARI -IR sources along with supplementary Spitzer and WISE data as well as pre-existing optical data. In this work, we derive new photo -z using a χ2 template-fitting method code, PHotometric Analysis for Redshift Estimate (Le Phare) and reliable photometry from 26 selected filters including HSC, AKARI , Canada–France–Hawaii Telescope, Maidanak, Kitt Peak National Observatory, Spitzer and WISE data. We take 2026 spectroscopic redshifts (spec -z) from all available spectroscopic surveys over the NEPW field to calibrate and assess the accuracy of the photo -z. At z < 1.5, we achieve a weighted photo -z dispersion of σΔ z /(1+ z) = 0.053 with η = 11.3 per cent catastrophic errors. [ABSTRACT FROM AUTHOR]

We present an 850- μ m mosaic map and extracted catalogue of submillimetre sources in the extended North Ecliptic Pole (NEP) region over about 2 deg2. The 850- μ m map is constructed using newly obtained observations by SCUBA-2 at the East Asian Observatory's James Clerk Maxwell Telescope, carried out using the observatory's large programme opportunities. The recent 850- μ m survey has extended the submillimetre data coverage by almost a factor of 4 compared to previous surveys, with a depth of |$\sigma _\text{rms}\, {=}\, 1.0$| – |$2.3\, {\rm mJy}\, {\rm beam}^{-1}$|⁠. The catalogue contains 549 sources selected above a significance level of 4σ, where the false-detection rate is 10 per cent; a higher threshold of 4.5σ is required in order to achieve a false-detection rate below 3 per cent, which results in 342 sources being selected. Despite the large spatial variation of the noise, the deboosted flux density of sources is comparable to results from the SCUBA-2 Cosmology Legacy Survey, which covered the central 0.6 deg2 of our survey area with better sensitivity. We construct the source counts at 850  μ m, finding results in agreement with other 850- μ m surveys in cosmological blank fields over S 850 = 4–15 mJy. We find a slight excess of bright galaxies (⁠|$S_{850}\, {\gt }\, 15$|  mJy), which can be considered to be at |$z_\text{phot}\, {=}\, 2$| –4. The 850- μ m data add valuable long-wavelength information to mid-infrared-selected sources from the AKARI NEP-deep and NEP-wide surveys, which will be helpful in preparing for future near-infrared to millimetre wavelength observations in the NEP region. Our 850- μ m mosaic map and source catalogue will be made publicly available. [ABSTRACT FROM AUTHOR]

The |$AKARI$| infrared (IR) space telescope conducted two surveys (Deep and Wide) in the North Ecliptic Pole (NEP) field to find more than 100 000 IR sources using its infrared camera (IRC). IRC's nine filters, which cover wavebands from 2 to 24 μ m continuously, make |$AKARI$| unique in comparison with other IR observatories such as |$Spitzer$| or |$WISE$|⁠. However, studies of the |$AKARI$| NEP-Wide field sources had been limited due to the lack of follow-up observations in the ultraviolet (UV) and optical. In this work, we present the Canada–France–Hawaii Telescope MegaPrime/MegaCam u -band source catalogue of the |$AKARI$| NEP-Wide field. The observations were taken in seven nights in 2015 and 2016, resulting in 82 observed frames covering 3.6 deg |$^2$|⁠. The data reduction, image processing, and source extraction were performed in a standard procedure using the elixir pipeline and the astromatic software, and eventually 351 635 sources have been extracted. The data quality is discussed in two regions (shallow and deep) separately, due to the difference in the total integration time (4520 and 13 910 s). The 5 |$\sigma$| limiting magnitude, seeing full width at half-maximum, and the magnitude at 50 per cent completeness are 25.38 mag (25.79 mag in the deep region), 0.82 arcsec (0.94 arcsec), and 25.06 mag (25.45 mag), respectively. The u -band data provide us with critical improvements to photometric redshifts and UV estimates of the precious infrared sources from the |$AKARI$| space telescope. [ABSTRACT FROM AUTHOR]

We investigate the evolution of the gas mass fraction for galaxies in the COSMOS field using submillimetre emission from dust at 850  μ m. We use stacking methodologies on the 850   μ m S2COSMOS map to derive the gas mass fraction of galaxies out to high redshifts, 0 ≤ z ≤ 5, for galaxies with stellar masses of |$10^{9.5} \lt M_* (\rm M_{\odot }) \lt 10^{11.75}$|⁠. In comparison to previous literature studies we extend to higher redshifts, include more normal star-forming galaxies (on the main sequence), and also investigate the evolution of the gas mass fraction split by star-forming and passive galaxy populations. We find our stacking results broadly agree with scaling relations in the literature. We find tentative evidence for a peak in the gas mass fraction of galaxies at around z ∼ 2.5–3, just before the peak of the star formation history of the Universe. We find that passive galaxies are particularly devoid of gas, compared to the star-forming population. We find that even at high redshifts, high stellar mass galaxies still contain significant amounts of gas. [ABSTRACT FROM AUTHOR]

By utilizing large-scale graph analytic tools implemented in the modern big data platform, apache spark , we investigate the topological structure of gravitational clustering in five different universes produced by cosmological N -body simulations with varying parameters: (1) a WMAP 5-yr compatible ΛCDM cosmology, (2) two different dark energy equation of state variants, and (3) two different cosmic matter density variants. For the big data calculations, we use a custom build of standalone Spark/Hadoop cluster at Korea Institute for Advanced Study and Dataproc Compute Engine in Google Cloud Platform with sample sizes ranging from 7 to 200 million. We find that among the many possible graph-topological measures, three simple ones: (1) the average of number of neighbours (the so-called average vertex degree) α, (2) closed-to-connected triple fraction (the so-called transitivity) |$\tau _\Delta$|⁠ , and (3) the cumulative number density n s ≥ 5 of subgraphs with connected component size s ≥ 5, can effectively discriminate among the five model universes. Since these graph-topological measures are directly related with the usual n -points correlation functions of the cosmic density field, graph-topological statistics powered by big data computational infrastructure opens a new, intuitive, and computationally efficient window into the dark Universe. [ABSTRACT FROM AUTHOR]

We investigate the impact of the number of filaments connected to the nodes of the cosmic web on the physical properties of their galaxies using the Sloan Digital Sky Survey. We compare these measurements to the cosmological hydrodynamical simulations H  orizon -(no)AGN and Simba. We find that more massive galaxies are more connected, in qualitative agreement with theoretical predictions and measurements in dark-matter-only simulations. The star formation activity and morphology of observed galaxies both display some dependence on the connectivity of the cosmic web at a fixed stellar mass: Less star forming and less rotation supported galaxies also tend to have higher connectivity. These results qualitatively hold both for observed and for virtual galaxies, and can be understood given that the cosmic web is the main source of fuel for galaxy growth. The simulations show the same trends at a fixed halo mass, suggesting that the geometry of filamentary infall impacts galaxy properties beyond the depth of the local potential well. Based on simulations, it is also found that active galactic nucleus feedback is key to reversing the relationship between stellar mass and connectivity at a fixed halo mass. Technically, connectivity is a practical observational proxy for past and present accretion (minor mergers or diffuse infall). [ABSTRACT FROM AUTHOR]

We study the dust properties of 192 nearby galaxies from the JINGLE survey using photometric data in the 22–850  |$\mu$| m range. We derive the total dust mass, temperature T , and emissivity index β of the galaxies through the fitting of their spectral energy distribution (SED) using a single modified blackbody model (SMBB). We apply a hierarchical Bayesian approach that reduces the known degeneracy between T and β. Applying the hierarchical approach, the strength of the T –β anticorrelation is reduced from a Pearson correlation coefficient R  = −0.79 to R  = −0.52. For the JINGLE galaxies we measure dust temperatures in the range 17−30 K and dust emissivity indices β in the range 0.6−2.2. We compare the SMBB model with the broken emissivity law modified blackbody (BMBB) and the two modified blackbody (TMBB) models. The results derived with the SMBB and TMBB are in good agreement, thus applying the SMBB, which comes with fewer free parameters, does not penalize the measurement of the cold dust properties in the JINGLE sample. We investigate the relation between T and β and other global galaxy properties in the JINGLE and Herschel Reference Survey (HRS) sample. We find that β correlates with the stellar mass surface density (R  = 0.62) and anticorrelates with the H  i mass fraction (M H  i / M *, R  = −0.65), whereas the dust temperature correlates strongly with the star formation rate normalized by the dust mass (R  = 0.73). These relations can be used to estimate T and β in galaxies with insufficient photometric data available to measure them directly through SED fitting. [ABSTRACT FROM AUTHOR]

We use the IllustrisTNG cosmological hydrodynamical simulation to study the evolution of star formation rate (SFR)–density relation over cosmic time. We construct several samples of galaxies at different redshifts from z  = 2.0 to z  = 0.0, which have the same comoving number density. The SFR of galaxies decreases with local density at z  = 0.0, but its dependence on local density becomes weaker with redshift. At z  ≳ 1.0, the SFR of galaxies increases with local density (reversal of the SFR–density relation), and its dependence becomes stronger with redshift. This change of SFR–density relation with redshift still remains even when fixing the stellar masses of galaxies. The dependence of SFR on the distance to a galaxy cluster also shows a change with redshift in a way similar to the case based on local density, but the reversal happens at a higher redshift, z  ∼ 1.5, in clusters. On the other hand, the molecular gas fraction always decreases with local density regardless of redshift at z  = 0.0–2.0 even though the dependence becomes weaker when we fix the stellar mass. Our study demonstrates that the observed reversal of the SFR–density relation at z  ≳ 1.0 can be successfully reproduced in cosmological simulations. Our results are consistent with the idea that massive, star-forming galaxies are strongly clustered at high redshifts, forming larger structures. These galaxies then consume their gas faster than those in low-density regions through frequent interactions with other galaxies, ending up being quiescent in the local universe. [ABSTRACT FROM AUTHOR]

We present the SCUBA-2 850 |$\mu$| m component of JINGLE, the new JCMT large survey for dust and gas in nearby galaxies, which with 193 galaxies is the largest targeted survey of nearby galaxies at 850  |$\mu$| m. We provide details of our SCUBA-2 data reduction pipeline, optimized for slightly extended sources, and including a calibration model adjusted to match conventions used in other far-infrared (FIR) data. We measure total integrated fluxes for the entire JINGLE sample in 10 infrared/submillimetre bands, including all WISE, Herschel -PACS, Herschel -SPIRE, and SCUBA-2 850  |$\mu$| m maps, statistically accounting for the contamination by CO(J = 3–2) in the 850  |$\mu$| m band. Of our initial sample of 193 galaxies, 191 are detected at 250  |$\mu$| m with a ≥5σ significance. In the SCUBA-2 850  |$\mu$| m band we detect 126 galaxies with ≥3σ significance. The distribution of the JINGLE galaxies in FIR/sub-millimetre colour–colour plots reveals that the sample is not well fit by single modified-blackbody models that assume a single dust-emissivity index (β). Instead, our new 850  |$\mu$| m data suggest either that a large fraction of our objects require β < 1.5, or that a model allowing for an excess of sub-mm emission (e.g. a broken dust emissivity law, or a very cold dust component ≲10 K) is required. We provide relations to convert FIR colours to dust temperature and β for JINGLE-like galaxies. For JINGLE the FIR colours correlate more strongly with star-formation rate surface-density rather than the stellar surface-density, suggesting heating of dust is greater due to younger rather than older stellar-populations, consistent with the low proportion of early-type galaxies in the sample. [ABSTRACT FROM AUTHOR]

JINGLE is a new JCMT legacy survey designed to systematically study the cold interstellar medium of galaxies in the local Universe. As part of the survey we perform 850 µm continuum measurements with SCUBA-2 for a representative sample of 193 Herschel -selected galaxies with M *> 109M⊙, as well as integrated CO(2–1) line fluxes with RxA3m for a subset of 90 of these galaxies. The sample is selected from fields covered by the Herschel- ATLAS survey that are also targeted by the MaNGA optical integral-field spectroscopic survey. The new JCMT observations combined with the multiwavelength ancillary data will allow for the robust characterization of the properties of dust in the nearby Universe, and the benchmarking of scaling relations between dust, gas, and global galaxy properties. In this paper we give an overview of the survey objectives and details about the sample selection and JCMT observations, present a consistent 30-band UV-to-FIR photometric catalogue with derived properties, and introduce the JINGLE Main Data Release. Science highlights include the non-linearity of the relation between 850 µm luminosity and CO line luminosity (log L CO(2–1)=  1.372 log L 850–1.376), and the serendipitous discovery of candidate z > 6 galaxies. [ABSTRACT FROM AUTHOR]

We investigate environmental effects on galaxy spin using the recent public data of Mapping Nearby Galaxies at APO (MaNGA) integral field spectroscopic survey containing ∼2800 galaxies. We measure the spin parameter of 1830 galaxies through the analysis of two-dimensional stellar kinematic maps within the effective radii, and obtain their large-scale (background mass density from 20 nearby galaxies) and small-scale (distance to and morphology of the nearest neighbour galaxy) environmental parameters for 1529 and 1767 galaxies, respectively. We first examine the mass dependence of galaxy spin, and find that the spin parameter of early-type galaxies decreases with stellar mass at log (M*/M⊙) ≳ 10, consistent with the results from previous studies. We then divide the galaxies into three subsamples using their stellar masses to minimize the mass effects on galaxy spin. The spin parameters of galaxies in each subsample do not change with background mass density, but do change with distance to and morphology of the nearest neighbour. In particular, the spin parameter of late-type galaxies decreases as early-type neighbours approach within the virial radius. These results suggest that the large-scale environments hardly affect the galaxy spin, but the small-scale environments such as hydrodynamic galaxy–galaxy interactions can play a substantial role in determining galaxy spin. [ABSTRACT FROM AUTHOR]

ABSTRACT We study the evolution of the galactic spin using data of high-redshift galaxies in the fields of the Great Observatories Origins Deep Survey. Through simple dynamical considerations we estimate the spin for the disc galaxies in our sample and find that its distribution is consistent with that found for nearby galaxies. Defining a dimensionless angular momentum parameter for the disc component of the galaxies (λd), we do not find signs of evolution in the redshift range 0.4 ≤ z ≤ 1.2. We find that the mass and environmental dependences of the spin of our high-redshift galaxies are similar to those of low- z galaxies, showing a strong dependence on mass, in the sense that low-mass systems present higher λd values than high-mass galaxies, with no significant dependence on the environmental density. These results lead us to conclude that although individual disc galaxies might occasionally suffer strong evolution, they evolve in such a way that the overall spin distribution of the galactic population remains constant from z ∼ 1 to the present epoch. [ABSTRACT FROM AUTHOR]

We present a study of the optical spectral properties of 115 ultraluminous infrared galaxies (ULIRGs) in the southern sky. Using the optical spectra obtained at the Cerro Tololo Inter-American Observatory (CTIO) 4 -m telescope and provided by the Two-degree Field (2dF) Galaxy Redshift Survey and the Six-degree Field (6dF) Galaxy Survey, we measure emission linewidths and fluxes for spectral classification. We determine the spectral types of ULIRGs with H measurement using the standard diagnostic diagrams. For ULIRGs without H measurement, we determine their spectral types using the plane of flux ratio between [O ] and H versus [O ] linewidth based on our new empirical criterion. This criterion is efficient to distinguish active galactic nuclei (AGNs) from non-AGN galaxies with completeness and reliability of about 90 per cent. The sample of 115 ULIRGs is found to consist of eight broad-line AGNs, 49 narrow-line AGNs and 58 non-AGNs. The AGN fraction is on average 50 per cent and increases with infrared luminosity and Infrared Astronomical Satellite ( IRAS) 25-60 m colour, consistent with previous studies. The IRAS 25-60 m colour distributions are significantly different between AGN and non-AGN ULIRGs, while their IRAS 60-100 m colour distributions are similar. [ABSTRACT FROM AUTHOR]

We study the effects of the cluster environment on galactic morphology by defining a dimensionless angular momentum parameter, , to obtain a quantitative and objective measure of galaxy type. The use of this physical parameter allows us to take the study of morphological transformations in clusters beyond the measurements of merely qualitative parameters, e.g. spiral/elliptical (S/E) ratios, to a more physical footing. To this end, we employ an extensive Sloan Digital Sky Survey sample (Data Release 7) with galaxies associated with Abell galaxy clusters. The sample contains 121 relaxed Abell clusters and over 51 000 individual galaxies, which guarantees a thorough statistical coverage over a wide range of physical parameters. We find that the median value tends to decrease as we approach the cluster centre, with different dependences according to the mass of the galaxies and the hosting cluster; low- and intermediate-mass galaxies show a strong dependence, while massive galaxies seem to show, at all radii, low values. By analysing trends in as functions of the nearest neighbour environment, clustercentric radius and velocity dispersion of clusters, we can identify clearly the leading physical processes at work. We find that in massive clusters ( km s), the interaction with the cluster central region dominates, whilst in smaller clusters galaxy-galaxy interactions are chiefly responsible for driving galactic morphological transformations. [ABSTRACT FROM AUTHOR]

We present a result of cross-correlating the Infrared Astronomical Satellite Faint Source Catalogue with the spectroscopic catalogues of galaxies in the Fourth Data Release of the Sloan Digital Sky Survey, the Final Data Release of the 2dF Galaxy Redshift Survey (2dFGRS) and the Second Data Release of the 6dF Galaxy Survey. We have identified 324 ultraluminous infrared galaxies (ULIRGs) including 190 newly discovered ULIRGs, and two hyperluminous infrared galaxies. Adding these new ULIRGs, we increase the number of known ULIRGs by about 30 per cent. The reliability of the cross-correlation is estimated using the likelihood ratio method. The incompleteness of our sample introduced by the identification procedure in this study is estimated to be about 5 per cent. Our sample covers the redshift range of with a median redshift of , which is larger than that of the sample of previously known ULIRGs. [ABSTRACT FROM AUTHOR]

We present an 850- μ m mosaic map and extracted catalogue of submillimetre sources in the extended North Ecliptic Pole (NEP) region over about 2 deg2. The 850- μ m map is constructed using newly obtained observations by SCUBA-2 at the East Asian Observatory's James Clerk Maxwell Telescope, carried out using the observatory's large programme opportunities. The recent 850- μ m survey has extended the submillimetre data coverage by almost a factor of 4 compared to previous surveys, with a depth of |$\sigma _\text{rms}\, {=}\, 1.0$| – |$2.3\, {\rm mJy}\, {\rm beam}^{-1}$|⁠. The catalogue contains 549 sources selected above a significance level of 4σ, where the false-detection rate is 10 per cent; a higher threshold of 4.5σ is required in order to achieve a false-detection rate below 3 per cent, which results in 342 sources being selected. Despite the large spatial variation of the noise, the deboosted flux density of sources is comparable to results from the SCUBA-2 Cosmology Legacy Survey, which covered the central 0.6 deg2 of our survey area with better sensitivity. We construct the source counts at 850  μ m, finding results in agreement with other 850- μ m surveys in cosmological blank fields over S 850 = 4–15 mJy. We find a slight excess of bright galaxies (⁠|$S_{850}\, {\gt }\, 15$|  mJy), which can be considered to be at |$z_\text{phot}\, {=}\, 2$| –4. The 850- μ m data add valuable long-wavelength information to mid-infrared-selected sources from the AKARI NEP-deep and NEP-wide surveys, which will be helpful in preparing for future near-infrared to millimetre wavelength observations in the NEP region. Our 850- μ m mosaic map and source catalogue will be made publicly available. [ABSTRACT FROM AUTHOR]