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Studying coupling between different galactic components is a challenging problem in galactic dynamics. Using basis function expansions (BFEs) and multichannel singular spectrum analysis (mSSA) as a means of dynamical data mining, we discover evidence for two multicomponent disc–halo dipole modes in a Milky-Way-like simulated galaxy. One of the modes grows throughout the simulation, while the other decays throughout the simulation. The multicomponent disc–halo modes are driven primarily by the halo, and have implications for the structural evolution of galaxies, including observations of lopsidedness and other non-axisymmetric structure. In our simulation, the modes create surface density features up to 10 per cent relative to the equilibrium model stellar disc. While the simulated galaxy was constructed to be in equilibrium, BFE + mSSA also uncovered evidence of persistent periodic signals incited by aphysical initial conditions disequilibrium, including rings and weak two-armed spirals, both at the 1 per cent level. The method is sensitive to distinct evolutionary features at and even below the 1 per cent level of surface density variation. The use of mSSA produced clean signals for both modes and disequilibrium, efficiently removing variance owing to estimator noise from the input BFE time series. The discovery of multicomponent halo–disc modes is strong motivation for application of BFE + mSSA to the rich zoo of dynamics of multicomponent interacting galaxies. [ABSTRACT FROM AUTHOR]

We compile published spectroscopic data and [O  iii ] magnitudes of almost 500 extragalactic planetary nebulae (PNe) in 13 galaxies of various masses and morphological types. This is the first paper of a series that aims to analyse the PN populations and their progenitors in these galaxies. Although the samples are not complete or homogeneous, we obtain some first findings through the comparison of a few intensity line ratios and nebular parameters. We find that the ionized masses and the luminosities in H β, L H β, of around 30 objects previously identified as PNe indicate that they are most likely compact H  ii regions. We find an anticorrelation between the electron densities and the ionized masses in M 31, M 33, and NGC 300 that suggests that most of the PNe observed in these galaxies are probably ionization bounded. This trend is absent in LMC and SMC suggesting that many of their PNe are density bounded. The He  ii λ4686/H β values found in many PNe in LMC and some in M 33 and SMC are higher than in the other galaxies. Photoionization models predict that these high values can only be reached in density bounded PNe. We also find that the brightest PNe in the sample are not necessarily the youngest since there is no correlation between electron densities and the H β luminosities. The strong correlation found between L H β and |$L_{[\rm {O}\, \small {III}] }$| implies that the so far not understood cut-off of the planetary nebula luminosity function (PNLF) based on [O  iii ] magnitudes can be investigated using L H β, a parameter much easier to study. [ABSTRACT FROM AUTHOR]

We study the late-time evolution of the central regions of two Milky Way (MW)-like simulations of galaxies formed in a cosmological context, one hosting a fast bar and the other a slow one. We find that bar length, R b, measurements fluctuate on a dynamical time-scale by up to 100 per cent, depending on the spiral structure strength and measurement threshold. The bar amplitude oscillates by about 15 per cent, correlating with R b. The Tremaine–Weinberg method estimates of the bars' instantaneous pattern speeds show variations around the mean of up to |$\sim \!20{{\ \rm per\ cent}}$|⁠ , typically anticorrelating with the bar length and strength. Through power spectrum analyses, we establish that these bar pulsations, with a period in the range ∼60–200 Myr, result from its interaction with multiple spiral modes, which are coupled with the bar. Because of the presence of odd spiral modes, the two bar halves typically do not connect at exactly the same time to a spiral arm, and their individual lengths can be significantly offset. We estimated that in about 50 per cent of bar measurements in MW-mass external galaxies, the bar lengths of SBab-type galaxies are overestimated by |$\sim \!15{{\ \rm per\ cent}}$| and those of SBbc types by |$\sim \!55{{\ \rm per\ cent}}$|⁠. Consequently, bars longer than their corotation radius reported in the literature, dubbed 'ultrafast bars', may simply correspond to the largest biases. Given that the Scutum–Centaurus arm is likely connected to the near half of the MW bar, recent direct measurements may be overestimating its length by 1–1.5 kpc, while its present pattern speed may be 5–10  |$\rm km\ s^{-1}\ kpc^{-1}$| smaller than its time-averaged value. [ABSTRACT FROM AUTHOR]

The Supernova Cosmology Project has conducted the 'See Change' programme, aimed at discovering and observing high-redshift (1.13 ≤ z ≤ 1.75) Type Ia supernovae (SNe Ia). We used multifilter Hubble Space Telescope (HST) observations of massive galaxy clusters with sufficient cadence to make the observed SN Ia light curves suitable for a cosmological probe of dark energy at z > 0.5. This See Change sample of SNe Ia with multi-colour light curves will be the largest to date at these redshifts. As part of the See Change programme, we obtained ground-based spectroscopy of each discovered transient and/or its host galaxy. Here, we present Very Large Telescope (VLT) spectra of See Change transient host galaxies, deriving their redshifts, and host parameters such as stellar mass and star formation rate. Of the 39 See Change transients/hosts that were observed with the VLT, we successfully determined the redshift for 26, including 15 SNe Ia at z > 0.97. We show that even in passive environments, it is possible to recover secure redshifts for the majority of SN hosts out to z  = 1.5. We find that with typical exposure times of 3−4 h on an 8-m-class telescope we can recover ∼75 per cent of SN Ia redshifts in the range of 0.97 < z < 1.5. Furthermore, we show that the combination of HST photometry and VLT spectroscopy is able to provide estimates of host galaxy stellar mass that are sufficiently accurate for use in a mass-step correction in the cosmological analysis. [ABSTRACT FROM AUTHOR]

Dwarfs are the largest population of galaxies in number in the nearby Universe. Deep spectroscopic data are still missing to obtain a better understanding of their formation and evolution processes. This study shows the results obtained from a spectroscopic campaign in the Perseus cluster. We have obtained 963 new galaxy spectra. We have measured the recessional velocity of the galaxies by using a cross-correlation technique. These data have been used to obtain the cluster membership, the dynamics of the galaxies, and the spectroscopic luminosity function (LF) of the cluster. The cluster membership was obtained by using the peak + gap technique, reporting a total of 403 galaxies as cluster members within 1.4 r 200. The mean velocity and velocity dispersion of the cluster galaxies are V c = 5258 km s−1 and σc = 1040 km s−1, respectively. We obtained M 200 = 1.2 × 1015 M⊙ and r 200 = 2.2 Mpc for this cluster. The clusters members were classified blue and red according to their g − r stellar colour. The velocity dispersion of these two families of galaxies is different, indicating that the blue galaxies can be classified as recently accreted into the cluster. We present the spectroscopic galaxy LF of the cluster. This function turned to be flat: α = 0.99 ± 0.06. In addition, blue and red galaxies show similar densities in the faint end of the LF. This indicates that Perseus does not have a population of red dwarf galaxias as large as other nearby clusters. We have compared the LF of the Perseus cluster with other spectroscopic LFs of nearby clusters and those from cosmological simulations. This comparison shows that the spectroscopic LF of nearby galaxy cluster is far from universal. [ABSTRACT FROM AUTHOR]

In the framework of an ongoing project aimed at searching for and studying eXtremely Metal-Poor (XMP) very gas-rich blue dwarfs in nearby voids, we conducted spectroscopy with the 11-m Southern African Large Telescope (SALT) of 26 candidates, preselected in the first paper of this series (PEPK19). For 23 of them, we detected oxygen lines, allowing us to estimate the gas O/H ratio. For 10 of them, the oxygen abundance is found to be very low, in the range of 12 + log (O/H) = 6.95–7.30 dex. Of those, four void dwarfs have 12 + log (O/H) < 7.19, or Z < Z⊙/30. For the majority of observed galaxies, the faint line [O  iii ] λ4363 Å used to estimate O/H with the direct T e method appeared either too noisy or was not detected. We therefore use the semi-empirical method of Izotov & Thuan for these spectra, or, when applicable, the new 'Strong line' method of Izotov et al. We present and discuss the results for all void dwarfs observed in this work. We also compare their O/H values with O/H values of ∼140 void galaxies available from our recent papers. We address the properties of the newly found unusual void XMP dwarfs and compare them with those for 10 known prototype void XMP objects. The latter small group is outstanding based on their very small mass fraction of stars (only 0.01–0.02 of the baryonic mass), the blue colours of stars in the outer body indicating a non-cosmological age for the main star-forming episode), and the low gas metallicity (several times lower than expected for their luminosity). [ABSTRACT FROM AUTHOR]

The epoch corresponding to a redshift of z ∼ 6.5 is close to full re-ionization of the Universe, and early enough to provide an intriguing environment to observe the early stage of large-scale structure formation. It is also an epoch that can be used to verify the abundance of a large population of low luminosity star-forming galaxies that are deemed responsible for cosmic re-ionization. Here, we present the results of follow-up multi-object spectroscopy using OSIRIS at Gran Telescopio Canarias of 16 Ly α emitter (LAE) candidates discovered in the Subaru/XMM Newton Deep Survey. We have securely confirmed 10 LAEs with sufficient signal-to-noise ratio of the Ly α emission line. The inferred star formation rates of the confirmed LAEs are on the low side, within the range 0.9–4.7 M⊙ yr−1. However, they show relatively high Ly α rest frame equivalent widths. Finally we have shown that the mechanical energy released by the star formation episodes in these galaxies is enough to create holes in the neutral hydrogen medium such that Lyman continuum photons can escape to the intergalactic medium, thus contributing to the re-ionization of the Universe. [ABSTRACT FROM AUTHOR]

In the cold dark matter (CDM) picture of structure formation, galaxy mass distributions are predicted to have a considerable amount of structure on small scales. Strong gravitational lensing has proven to be a useful tool for studying this small-scale structure. Much of the attention has been given to detecting individual dark matter subhaloes through lens modelling, but recent work has suggested that the full population of subhaloes could be probed using a power spectrum analysis. In this paper, we quantify the power spectrum of small-scale structure in simulated galaxies, with the goal of understanding theoretical predictions and setting the stage for using measurements of the power spectrum to test dark matter models. We use a sample of simulated galaxies generated from the galacticus semi-analytic model to determine the power spectrum distribution first in the CDM paradigm and then in a warm dark matter scenario. We find that a measurement of the slope and amplitude of the power spectrum on galaxy strong lensing scales (k ∼ 1 kpc−1) could be used to distinguish between CDM and alternate dark matter models, especially if the most massive subhaloes can be directly detected via gravitational imaging. [ABSTRACT FROM AUTHOR]

We use the DECaLS DR3 survey photometry matched to the SDSS-III/BOSS DR12 spectroscopic catalogue to investigate the morphology and stellar mass–size relation of luminous red galaxies within the CMASS and LOWZ galaxy samples in the redshift range 0.2 < $$z$$ < 0.7. The large majority of both samples is composed of early-type galaxies with De Vaucouleurs profiles, while only less than 20 per cent are late-type exponentials. We calibrate DECaLS effective radii using the higher-resolution CFHT/MegaCam observations and optimize the correction for each morphological type. By cross-matching the photometric properties of the early-type population with the Portsmouth stellar mass catalogue, we are able to explore the high-mass end of the distribution using a large sample of 322994 galaxies over 4380 deg2. We find a clear correlation between the sizes and stellar masses of these galaxies, which appears flatter than previous estimates at lower masses. The sizes of these early-type galaxies do not exhibit significant evolution within the BOSS redshift range, but a slightly declining redshift trend is found when these results are combined with $$z$$ ∼ 0.1 SDSS measurements at the high-mass end. The synergy between BOSS and DECaLS has important applications in other fields, including galaxy clustering and weak lensing. [ABSTRACT FROM AUTHOR]

Large-scale surveys of galaxies require accurate theoretical predictions of the dark matter clustering for thousands of mock galaxy catalogues. We demonstrate that this goal can be achieved with the new Parallel Particle-Mesh (PM) N -body code GLAM at a very low computational cost. We run ∼22 000 simulations with ∼2 billion particles that provide ∼1 per cent accuracy of the dark matter power spectra P (k) for wavenumbers up to k ∼ 1  h  Mpc−1. Using this large data set we study the power spectrum covariance matrix. In contrast to many previous analytical and numerical results, we find that the covariance matrix normalized to the power spectrum C (k, k ′)/ P (k) P (k ′) has a complex structure of non-diagonal components: an upturn at small k, followed by a minimum at k  ≈ 0.1–0.2  h  Mpc−1, and a maximum at k  ≈ 0.5–0.6  h  Mpc−1. The normalized covariance matrix strongly evolves with redshift: C (k, k ′) ∝ δα(t) P (k) P (k ′), where δ is the linear growth factor and α ≈ 1–1.25, which indicates that the covariance matrix depends on cosmological parameters. We also show that waves longer than $$1\,h^{-1}\rm{\,Gpc}$$ have very little impact on the power spectrum and covariance matrix. This significantly reduces the computational costs and complexity of theoretical predictions: relatively small volume $${\sim } (1\,h^{-1}\rm{\,Gpc})^3$$ simulations capture the necessary properties of dark matter clustering statistics. As our results also indicate, achieving ∼1 per cent errors in the covariance matrix for k < 0.50  h  Mpc−1 requires a resolution better than $$\epsilon \sim 0.5\,h^{-1}\rm{\,Mpc}$$. [ABSTRACT FROM AUTHOR]

We present observations with the Cosmic Origins Spectrograph (COS) onboard the Hubble Space Telescope of five star-forming galaxies at redshifts $$z$$ in the range 0.2993–0.4317 and with high emission-line flux ratios O32 = [O  iii ] λ5007/[O  ii ] λ3727 ∼ 8–27 aiming to detect the Lyman continuum (LyC) emission. We detect LyC emission in all galaxies with the escape fractions f esc(LyC) in a range of 2–72 per cent. A narrow Lyα emission line with two peaks in four galaxies and with three peaks in one object is seen in medium-resolution COS spectra with a velocity separation between the peaks V sep varying from ∼153 to ∼345 km s−1. We find a general increase of the LyC escape fraction with increasing O32 and decreasing stellar mass M ⋆, but with a large scatter of f esc(LyC). A tight anticorrelation is found between f esc(LyC) and V sep making V sep a good parameter for the indirect determination of the LyC escape fraction. We argue that one possible source driving the escape of ionizing radiation is stellar winds and radiation from hot massive stars. [ABSTRACT FROM AUTHOR]

The Galactic Archaeology with HERMES (GALAH) survey is a large-scale stellar spectroscopic survey of the Milky Way, designed to deliver complementary chemical information to a large number of stars covered by the Gaia mission. We present the GALAH second public data release (GALAH DR2) containing 342 682 stars. For these stars, the GALAH collaboration provides stellar parameters and abundances for up to 23 elements to the community. Here we present the target selection, observation, data reduction, and detailed explanation of how the spectra were analysed to estimate stellar parameters and element abundances. For the stellar analysis, we have used a multistep approach. We use the physics-driven spectrum synthesis of Spectroscopy Made Easy (SME) to derive stellar labels (T eff, log  g, [Fe/H], [X/Fe], v mic, v sin  i, $$A_{K_S}$$) for a representative training set of stars. This information is then propagated to the whole sample with the data-driven method of The Cannon. Special care has been exercised in the spectral synthesis to only consider spectral lines that have reliable atomic input data and are little affected by blending lines. Departures from local thermodynamic equilibrium (LTE) are considered for several key elements, including Li, O, Na, Mg, Al, Si, and Fe, using 1D marcs stellar atmosphere models. Validation tests including repeat observations, Gaia benchmark stars, open and globular clusters, and K2 asteroseismic targets lend confidence to our methods and results. Combining the GALAH DR2 catalogue with the kinematic information from Gaia will enable a wide range of Galactic Archaeology studies, with unprecedented detail, dimensionality, and scope. [ABSTRACT FROM AUTHOR]

The spectrum of a galaxy contains information about its physical properties. Classifying spectra using templates helps to elucidate the nature of a galaxy’s energy sources. In this paper, we investigate the use of self-organizing maps in classifying galaxy spectra against templates. We trained semi-supervised self-organizing map networks using a set of templates covering the wavelength range from far ultraviolet to near-infrared. The trained networks were used to classify the spectra of a sample of 142 galaxies with 0.5 < $$z$$ < 1 and the results compared to classifications performed using K -means clustering, a supervised neural network, and chi-squared minimization. Spectra corresponding to quiescent galaxies were more likely to be classified similarly by all methods while starburst spectra showed more variability. Compared to classification using chi-squared minimization or the supervised neural network, the galaxies classed together by the self-organizing map had more similar spectra. The class ordering provided by the 1D self-organizing maps corresponds to an ordering in physical properties, a potentially important feature for the exploration of large data sets. [ABSTRACT FROM AUTHOR]

We report results from 21-cm intensity maps acquired from the Parkes radio telescope and cross-correlated with galaxy maps from the 2dF galaxy survey. The data span the redshift range 0.057 <  z  < 0.098 and cover approximately 1300 deg2 over two long fields. Cross-correlation is detected at a significance of 5.7 σ. The amplitude of the cross-power spectrum is low relative to the expected dark matter power spectrum, assuming a neutral hydrogen (H  i) bias and mass density equal to measurements from the ALFALFA survey. The decrement is pronounced and statistically significant at small scales. At k  ∼ 1.5   h  Mpc−1, the cross-power spectrum is more than a factor of 6 lower than expected, with a significance of 15.3 σ. This decrement indicates a lack of clustering of neutral hydrogen (H  i), a small correlation coefficient between optical galaxies and H  i, or some combination of the two. Separating 2dF into red and blue galaxies, we find that red galaxies are much more weakly correlated with H  i on k  ∼ 1.5 h  Mpc−1 scales, suggesting that H  i is more associated with blue star-forming galaxies and tends to avoid red galaxies. [ABSTRACT FROM AUTHOR]

We present an analysis of the spatial distribution and dynamics of neutral hydrogen gas around galaxies using new X-Shooter observations of z ~ 2.5-4 quasars. Adding the X-Shooter data to our existing data set of high-resolution quasar spectroscopy, we use a total sample of 29 quasars alongside ~1700 Lyman Break Galaxies (LBGs) in the redshift range 2 ≲ z ≲ 3.5. We measure the Lyα forest auto-correlation function, finding a clustering length of s0 = 0.081 ± 0.006 h-1 Mpc, and the cross-correlation function with LBGs, finding a cross-clustering length of s0 = 0.27 ± 0.14 h-1 Mpc and power-law slope γ = 1.1 ± 0.2. Our results highlight the weakly clustered nature of neutral hydrogren systems in the Lyα forest. Building on this, we make a first analysis of the dependence of the clustering on absorber strength, finding a clear preference for stronger Lyα forest absorption features to be more strongly clustered around the galaxy population, suggesting that they trace on average higher mass haloes. Using the projected and 2-D cross-correlation functions, we constrain the dynamics of Lyα forest clouds around z ~ 3 galaxies. We find a significant detection of large-scale infall of neutral hydrogen, with a constraint on the Lyα forest infall parameter of βF = 1.02 ± 0.22. [ABSTRACT FROM AUTHOR]

The computation of transmission spectra is a central ingredient in the study of exoplanetary atmospheres. First, we revisit the theory of transmission spectra, unifying ideas from several workers in the literature. Transmission spectra lack an absolute normalization due to the a priori unknown value of a reference transit radius, which is tied to an unknown reference pressure. We show that there is a degeneracy between the uncertainty in the transit radius, the assumed value of the reference pressure (typically set to 10 bar) and the inferred value of the water abundance when interpreting a Wide-Field Camera 3 (WFC3) transmission spectrum. Secondly, we show that the transmission spectra of isothermal atmospheres are nearly isobaric. We validate the isothermal, isobaric analytical formula for the transmission spectrum against full numerical calculations and show that the typical errors are∼0.1 per cent (∼10 ppm) within theWFC3 range of wavelengths for temperatures of 1500 K (or higher). Thirdly, we generalize the previous expression for the transit radius to include a small temperature gradient. Finally, we analyse the measured WFC3 transmission spectrum of WASP-12b and demonstrate that we obtain consistent results with the retrieval approach of Kreidberg et al., if the reference transit radius and reference pressure are fixed to assumed values. The unknown functional relationship between the reference transit radius and reference pressure implies that it is the product of thewater abundance and reference pressure that is being retrieved from the data, and not just the water abundance alone. This degeneracy leads to a limitation on how accurately we may extract molecular abundances from transmission spectra using WFC3 data alone. We suggest an approximate expression for this relationship. Finally, we compare our study to that of Griffith and discuss why the degeneracy was missed in previous retrieval studies. [ABSTRACT FROM AUTHOR]

We present cosmological results from the final galaxy clustering data set of the Baryon Oscillation Spectroscopic Survey, part of the Sloan Digital Sky Survey III. Our combined galaxy sample comprises 1.2 million massive galaxies over an effective area of 9329 deg2 and volume of 18.7 Gpc3, divided into three partially overlapping redshift slices centred at effective redshifts 0.38, 0.51 and 0.61. We measure the angular diameter distance DM and Hubble parameterHfrom the baryon acoustic oscillation (BAO) method, in combinationwith a cosmic microwave background prior on the sound horizon scale, after applying reconstruction to reduce non-linear effects on the BAO feature. Using the anisotropic clustering of the pre-reconstruction density field, we measure the product DMH from the Alcock-Paczynski (AP) effect and the growth of structure, quantified by fΟ8(z), from redshift-space distortions (RSD). We combine individual measurements presented in seven companion papers into a set of consensus values and likelihoods, obtaining constraints that are tighter and more robust than those from any one method; in particular, the AP measurement from sub-BAO scales sharpens constraints from post-reconstruction BAOs by breaking degeneracy between DM and H. Combined with Planck 2016 cosmic microwave background measurements, our distance scale measurements simultaneously imply curvature ΩK = 0.0003 ± 0.0026 and a dark energy equation-of-state parameter w =-1.01 ± 0.06, in strong affirmation of the spatially flat cold dark matter (CDM) model with a cosmological constant (ΔCDM). Our RSD measurements of fs8, at 6 per cent precision, are similarly consistent with this model. When combined with supernova Ia data, we find H0 = 67.3 ± 1.0 kms-1 Mpc-1 even for our most general dark energy model, in tension with some direct measurements. Adding extra relativistic species as a degree of freedom loosens the constraint only slightly, to H0 = 67.8 ± 1.2 kms-1 Mpc-1. Assuming flat ΔCDM, we find Ωm = 0.310 ± 0.005 and H0 = 67.6 ± 0.5 kms-1 Mpc-1 and we find a 95 per cent upper limit of 0.16 eV c-2 on the neutrino mass sum. [ABSTRACT FROM AUTHOR]

We have studied the environment of the FU Ori type star V582 Aur. Our aim is to explore the star-forming region associated with this young eruptive star. Using slitless spectroscopy, we searched for Hα emission stars within a field of 11.5 arcmin x 11.5 arcmin, centred on V582 Aur. Based on UKIDSS and Spitzer Space Telescope data, we further selected infrared-excess young stellar object candidates. In all, we identified 68 candidate low-mass young stars, 16 of which exhibited Hα emission in the slitless spectroscopic images. The colour--magnitude diagram of the selected objects, based on the IPHAS data, suggests that they are low-mass pre-main-sequence stars associated with the Aur OB& 1 association, located at a distance of 1.3& kpc from Sun. The bright-rimmed globules in the local environment of V582 Aur probably belong to the dark cloud LDN 1516. Our results suggest that star formation in these globules might have been triggered by the radiation field of a few hot members of Aur OB& 1. The bolometric luminosity of V582 Aur, based on archival photometric data and on the adopted distance, is 150–320& L⊙. [ABSTRACT FROM AUTHOR]

We present quasar bolometric corrections using the [OIII]λ5007 narrow emission line luminosity based on the detailed spectral energy distributions of 53 bright quasars at low to moderate redshift (0.0345 < z < 1.0002). We adopted two functional forms to calculate Liso, the bolometric luminosity determined under the assumption of isotropy: Liso=AL[OIII] for comparison with the literature and log(Liso)=B+Clog(L[OIII]), which better characterizes the data. We also explored whether 'Eigenvector 1 (EV1)', which describes the range of quasar spectral properties and quantifies their diversity, introduces scatter into the L[OIII] -Liso relationship. We found that the [OIII] bolometric correction can be significantly improved by adding a term including the equivalent width ratio RFeII ≡EWFeII/EWHβ, which is an EV1 indicator. Inclusion of RFeII in predicting Liso is significant at nearly the 3σ level and reduces the scatter and systematic offset of the luminosity residuals. Typically, [OIII] bolometric corrections are adopted for Type 2 sources where the quasar continuum is not observed and in these cases, RFeII cannot be measured. We searched for an alternative measure of EV1 that could be measured in the optical spectra of Type 2 sources but were unable to identify one. Thus, the main contribution of this work is to present an improved [OIII] bolometric correction based on measured bolometric luminosities and highlight the EV1 dependence of the correction in Type 1 sources. [ABSTRACT FROM AUTHOR]

We have searched for HI 21-cm absorption in 11 strong MgII systems (Wr(Mg II λ2796) ≥1Å) at 0.3 < z < 0.5 using the Giant Metrewave Radio Telescope. We have detected HI 21-cm absorption in two of these systems. From the integrated optical depth (∫ τdv), we estimate N(H I) = 43 ± 2 and 9 ± 2 in units of 1019 cm-2 for the absorbers towards J1428+2103 (zabs = 0.3940) and J1551+0713 (zabs = 0.3289), respectively, assuming spin temperature Ts = 100 K and gas covering factor Cf = 1. The velocity width of the HI absorption towards J1428+2103 and J1551+0713 indicates that the gas temperature is <1600 and <350 K, respectively. The 3σ upper limits on ∫ τdv in the case of the HI 21-cm non-detections indicate that these Mg II absorbers are likely to arise from sub-damped Lyman α systems, when we assume Ts = 100 K and Cf = 1. This is verified for one of the systems which has N(H I) measurement using Lyman α absorption detected in the ultraviolet spectrum.We estimate the detection rate of HI 21-cm absorption in strong MgII systems in our sample to be 0.18+0.24 −0.12 at z ~ 0.35, for an integrated optical depth sensitivity of ≤0.3 kms-1. Comparing with the results of HI 21-cm absorption surveys in strong MgII systems at higher redshifts from the literature, we do not find any significant evolution in the incidence and number density per unit redshift of HI 21-cm absorbers in strong MgII systems over 0.3 < z < 1.5. [ABSTRACT FROM AUTHOR]

Even as our measurements of cosmological parameters improve, the physical nature of the dark sector of the universe largely remains a mystery. Many effects of dark sector models are most prominent at very large scales and will rely on future galaxy surveys to elucidate. In this paper, we compare the topological properties of the large-scale dark matter distribution in a number of cosmological models using hydrodynamical simulations and the cosmological genus statistic. Genus curves are computed from z = 11 to 0 for ⋀ cold dark matter (⋀CDM), quintessence and warm dark matter (WDM) models, over a scale range of 1-20 h-1 Mpc. The curves are analysed in terms of their Hermite spectra to describe the power contained in non-Gaussian deformations to the cosmological density field. We find that the ⋀CDM and ⋀WDM models produce nearly identical genus curves indicating no topological differences in structure formation. The quintessence model, which differs solely in its expansion history, produces significant differences in the strength and redshift evolution of non-Gaussian modes associated with higher cluster abundances and lower void abundances. These effects are robust to cosmic variance and are characteristically different from those produced by tweaking the parameters of a ⋀CDM model. Given the simplicity and similarity of the models, detecting these discrepancies represents a promising avenue for understanding the effect of non-standard cosmologies on large-scale structure. [ABSTRACT FROM AUTHOR]

We present the second release of value-added catalogues of the LAMOST Spectroscopic Survey of the Galactic Anticentre (LSS-GAC DR2). The catalogues present values of radial velocity Vr, atmospheric parameters - effective temperature Teff, surface gravity log g, metallicity [Fe/H], α-element to iron (metal) abundance ratio [α/Fe] ([α/M]), elemental abundances [C/H] and [N/H] and absolute magnitudes MV and MKs deduced from 1.8 million spectra of 1.4 million unique stars targeted by the LSS-GAC since 2011 September until 2014 June. The catalogues also give values of interstellar reddening, distance and orbital parameters determined with a variety of techniques, as well as proper motions and multiband photometry from the far-UV to the mid-IR collected from the literature and various surveys. Accuracies of radial velocities reach 5 km s-1 for the late-type stars, and those of distance estimates range between 10 and 30 per cent, depending on the spectral signal-to-noise ratios. Precisions of [Fe/H], [C/H] and [N/H] estimates reach 0.1 dex, and those of [α/Fe] and [α/M] reach 0.05 dex. The large number of stars, the contiguous sky coverage, the simple yet non-trivial target selection function and the robust estimates of stellar radial velocities and atmospheric parameters, distances and elemental abundances make the catalogues a valuable data set to study the structure and evolution of the Galaxy, especially the solar-neighbourhood and the outer disc. [ABSTRACT FROM AUTHOR]

Nearly all Galactic globular clusters host stars that display characteristic abundance anticorrelations, like the O-rich/Na-poor pattern typical of field halo stars, together with O-poor/Narich additional components. A recent spectroscopic investigation questioned the presence of O-poor/Na-rich stars amongst a sample of asymptotic giant branch (AGB) stars in the cluster M4, at variance with the spectroscopic detection of a O-poor/Na-rich component along both the cluster red giant branch (RGB) and horizontal branch. This is contrary to what is expected from the cluster horizontal branch morphology and horizontal branch stellar evolution models. Here, we have investigated this issue by employing the CUBI = (U - B) - (B - I) index, that previous studies have demonstrated to be very effective in separating multiple populations along both the RGB and AGB sequences. We confirm previous results that the RGB is intrinsically broad in the V-CUBI diagram, with the presence of two components that nicely correspond to the two populations identified by high-resolution spectroscopy. We find that AGB stars are distributed over a wide range of CUBI values, in close analogy with what is observed for the RGB, demonstrating that the AGB of M4 also hosts multiple stellar populations. [ABSTRACT FROM AUTHOR]

The narrow-line Seyfert 1 galaxy NGC 4051 is known to exhibit significant X-ray spectral/ flux variations and have a number of emission/absorption features. X-ray observations have revealed that these absorption features are blueshifted, which indicates that NGC 4051 has warm absorber outflow. In order to constrain physical parameters of the warm absorber outflow, we analyse the archival data with the longest exposure taken by XMM-Newton in 2009.We calculate the root-mean-square (rms) spectra with the grating spectral resolution for the first time. The rms spectra have a sharp peak and several dips, which can be explained by variable absorption features and non-variable emission lines; a lower ionized warm absorber (WA1: log ξ = 1.5, υ = -650 km s-1) shows large variability, whereas higher ionized warm absorbers (WA2: log ξ = 2.5, υ =-4100 km s-1, WA3: logξ = 3.4, υ =-6100 km s-1) show little variability. WA1 shows the maximum variability at a time-scale of ~104 s, suggesting that the absorber locates at ~103 times of the Schwarzschild radius. The depth of the absorption features due to WA1 and the observed soft X-ray flux are anticorrelated in several observational sequences, which can be explained by variation of partial covering fraction of the double-layer blobs that are composed of the Compton-thick core and the ionized layer (=WA1). WA2 and WA3 show little variability and presumably extend uniformly in the line of sight. The present result shows that NGC 4051 has two types of the warm absorber outflows; the static, high-ionized and extended line-driven disc winds and the variable, low-ionized and clumpy double-layer blobs. [ABSTRACT FROM AUTHOR]

We present infrared views of the environmental effects on the dust properties in star-forming (SF) galaxies at z ~ 0, using the AKARI Far-Infrared Surveyor all-sky map and the large spectroscopic galaxy sample from Sloan Digital Sky Survey (SDSS) Data Release 7 (DR7). We restrict the sample to those within the redshift range of 0.05 < z < 0.07 and the stellar mass range of 9.2 < log10(M*/M☉). We select SF galaxies based on their Hα equivalent width (EWHα > 4 Å) and emission line flux ratios. We perform far-infrared (FIR) stacking analyses by splitting the SDSS SF galaxy sample according to their stellar mass, specific star formation rate (SSFRSDSS), and environment. We derive total infrared luminosity (LIR) for each subsample using the average flux densities at WIDE-S (90 μm) and WIDE-L (140 μm) bands, and then compute infrared (IR)-based SFR (SFRIR) from LIR. We find a mild decrease of IR-based SSFR (SSFRIR) amongst SF galaxies with increasing local density (~0.1-dex level at maximum), which suggests that environmental effects do not instantly shut down the SF activity in galaxies. We also derive average dust temperature (Tdust) using the flux densities at 90 and 140 μm bands. We confirm a strong positive correlation between Tdust and SSFRIR, consistent with recent studies. The most important finding of this study is that we find a marginal trend that Tdust increases with increasing environmental galaxy density. Although the environmental trend is much milder than the SSFR-Tdust correlation, our results suggest that the environmental density may affect the dust temperature in SF galaxies, and that the physical mechanism which is responsible for this phenomenon is not necessarily specific to cluster environments because the environmental dependence of Tdust holds down to relatively low-density environments. [ABSTRACT FROM AUTHOR]

We present a method of calibrating the properties of photometric redshift bins as part of a larger nested sampling analysis for the inference of cosmological parameters. The redshift bins are characterized by their mean and variance, which are varied as free parameters and marginalized over when obtaining the cosmological parameters. We demonstrate that the likelihood function for cross-correlations in an angular power spectrum framework tightly constrains the properties of bins such that they may be well determined, reducing their influence on cosmological parameters and avoiding the bias from poorly estimated redshift distributions. We demonstrate that even with only three photometric and three spectroscopic bins, we can recover accurate estimates of the mean redshift of a bin to within Δμ ≈ 3-4 × 10-3 and the width of the bin to Δσ ≈ 1 × 10-3 for galaxies near z = 1. This indicates that we may be able to bring down the photometric redshift errors to a level which is in line with the requirements for the next generation of cosmological experiments. [ABSTRACT FROM AUTHOR]

Since the volume accessible to galaxy surveys is fundamentally limited, it is extremely important to analyse available data in the most optimal fashion. One way of enhancing the cosmological information extracted from the clustering of galaxies is by weighting the galaxy field. The most widely used weighting schemes assign weights to galaxies based on the average local density in the region (FKP weights) and their bias with respect to the dark matter field (PVP weights). They are designed to minimize the fractional variance of the galaxy power-spectrum. We demonstrate that the currently used bias dependent weighting scheme can be further optimized for specific cosmological parameters. We develop a procedure for computing the optimal weights and test them against mock catalogues for which the values of all fitting parameters, as well as the input power-spectrum are known. We show that by applying these weights to the joint power-spectrum of emission line galaxies and luminous red galaxies from the Dark Energy Spectroscopic Instrument survey, the variance in the measured growth rate parameter can be reduced by as much as 36 per cent. [ABSTRACT FROM AUTHOR]

The low-frequency radio spectra of the hotspots within powerful radio galaxies can provide valuable information about the physical processes operating at the site of the jet termination. These processes are responsible for the dissipation of jet kinetic energy, particle acceleration, and magnetic-field generation. Here, we report new observations of the powerful radio galaxy Cygnus A using the Low Frequency Array (LOFAR) between 109 and 183 MHz, at an angular resolution of ∼3.5 arcsec. The radio emission of the lobes is found to have a complex spectral index distribution, with a spectral steepening found towards the centre of the source. For the first time, a turnover in the radio spectrum of the two main hotspots of Cygnus A has been directly observed. By combining our LOFAR imaging with data from the Very Large Array at higher frequencies, we show that the very rapid turnover in the hotspot spectra cannot be explained by a low-energy cut-off in the electron energy distribution, as has been previously suggested. Thermal (free-free) absorption or synchrotron self-absorption models are able to describe the low-frequency spectral shape of the hotspots; however, as with previous studies, we find that the implied model parameters are unlikely, and interpreting the spectra of the hotspots remains problematic. [ABSTRACT FROM AUTHOR]

The Lockman Hole is a well-studied extragalactic field with extensive multi-band ancillary data covering a wide range in frequency, essential for characterizing the physical and evolutionary properties of the various source populations detected in deep radio fields (mainly star-forming galaxies and AGNs). In this paper, we present new 150-MHz observations carried out with the LOw-Frequency ARray (LOFAR), allowing us to explore a new spectral window for the faint radio source population. This 150-MHz image covers an area of 34.7 square degrees with a resolution of 18.6×14.7 arcsec and reaches an rms of 160 μJy beam-1 at the centre of the field. As expected for a low-frequency selected sample, the vast majority of sources exhibit steep spectra, with a median spectral index of α1400 150 = -0.78 ± 0.015. The median spectral index becomes slightly flatter (increasing from α1400 150 = -0.84 to α1400 150 = -0.75) with decreasing flux density down to S150 ~10 mJy before flattening out and remaining constant below this flux level. For a bright subset of the 150-MHz selected sample, we can trace the spectral properties down to lower frequencies using 60-MHz LOFAR observations, finding tentative evidence for sources to become flatter in spectrum between 60 and 150 MHz. Using the deep, multi-frequency data available in the Lockman Hole, we identify a sample of 100 ultra-steepspectrum sources and 13 peaked-spectrum sources.We estimate that up to 21 per cent of these could have z > 4 and are candidate high-z radio galaxies, but further follow-up observations are required to confirm the physical nature of these objects. [ABSTRACT FROM AUTHOR]

High-redshift radio-loud quasars are used to, among other things, test the predictions of cosmological models, set constraints on black hole growth in the early Universe and understand galaxy evolution. Prior to this paper, 20 extragalactic radio sources at redshifts above 4.5 have been imaged with very long baseline interferometry (VLBI). Here, we report on observations of an additional ten z > 4.5 sources at 1.7 and 5 GHz with the European VLBI Network, thereby increasing the number of imaged sources by 50 per cent. Combining our newly observed sources with those from the literature, we create a substantial sample of 30 z > 4.5 VLBI sources, allowing us to study the nature of these objects. Using spectral indices, variability and brightness temperatures, we conclude that of the 27 sources with sufficient information to classify, the radio emission from one source is from star formation, 13 are flat-spectrum radio quasars and 13 are steep-spectrum sources. We also argue that the steep-spectrum sources are off-axis (unbeamed) radio sources with rest-frame self-absorption peaks at or below GHz frequencies and that these sources can be classified as gigahertz peaked-spectrum and megahertz peaked-spectrum sources. [ABSTRACT FROM AUTHOR]

We present near-infrared (NIR) spectroscopic observations in the wavelength range 0.90- 2.40 μm of 18 low-metallicity blue compact dwarf (BCD) galaxies and six HII regions in spiral and interacting galaxies. Hydrogen and helium emission lines are detected in all spectra, while H2 and iron emission lines are detected in most spectra. The NIR data for all objects have been supplemented by optical spectra. In all objects, except perhaps for the highest metallicity ones, we find that the extinctions A(V) in the optical and NIR ranges are similar, implying that the NIR hydrogen emission lines in low-metallicity BCDs do not reveal more star formation than seen in the optical. We conclude that emission-line spectra of low-metallicity BCDs in the ~0.36-2.40 μm wavelength range are emitted by a relatively transparent ionized gas. The H2 emission-line fluxes can be accounted for by fluorescence in most of the observed galaxies. We find a decrease of the H2 2.122 μm emission line relative to the Br? line with increasing ionization parameter. This indicates an efficient destruction of H2 by the stellar ultraviolet radiation. The intensities of the [Fe II] 1.257 and 1.644 μm emission lines in the spectra of all galaxies, but one, are consistent with the predictions of CLOUDYstellar photoionization models. There is thus no need to invoke shock excitation for these lines, and they are not necessarily shock indicators in low-metallicity high-excitation BCDs. The intensity of the He I 2.058 μm emission line is lower in high-excitation BCDs with lower neutral gas column densities and higher turbulent motions. [ABSTRACT FROM AUTHOR]

We develop a Bayesian hierarchical modelling approach for cosmic shear power spectrum inference, jointly sampling from the posterior distribution of the cosmic shear field and its (tomographic) power spectra. Inference of the shear power spectrum is a powerful intermediate product for a cosmic shear analysis, since it requires very few model assumptions and can be used to perform inference on a wide range of cosmological models a posteriori without loss of information. We show that joint posterior for the shear map and power spectrum can be sampled effectively by Gibbs sampling, iteratively drawing samples from the map and power spectrum, each conditional on the other. This approach neatly circumvents difficulties associated with complicated survey geometry and masks that plague frequentist power spectrum estimators, since the power spectrum inference provides prior information about the field in masked regions at every sampling step. We demonstrate this approach for inference of tomographic shear E-mode, B-mode and EB-cross power spectra from a simulated galaxy shear catalogue with a number of important features; galaxies distributed on the sky and in redshift with photometric redshift uncertainties, realistic random ellipticity noise for every galaxy and a complicated survey mask. The obtained posterior distributions for the tomographic power spectrum coefficients recover the underlying simulated power spectra for both E- and B-modes. [ABSTRACT FROM AUTHOR]

In the low-redshift Universe (z < 0.3), our view of galaxy evolution is primarily based on fibre optic spectroscopy surveys. Elaborate methods have been developed to address aperture effects when fixed aperture sizes only probe the inner regions for galaxies of ever decreasing redshift or increasing physical size. These aperture corrections rely on assumptions about the physical properties of galaxies. The adequacy of these aperture corrections can be tested with integralfield spectroscopic data. We use integral-field spectra drawn from 1212 galaxies observed as part of the SAMI Galaxy Survey to investigate the validity of two aperture correction methods that attempt to estimate a galaxy's total instantaneous star formation rate.We show that biases arise when assuming that instantaneous star formation is traced by broad-band imaging, and when the aperture correction is built only from spectra of the nuclear region of galaxies. These biases may be significant depending on the selection criteria of a survey sample. Understanding the sensitivities of these aperture corrections is essential for correct handling of systematic errors in galaxy evolution studies. [ABSTRACT FROM AUTHOR]

We extend the catalogue of two-dimensional, Point-Spread-Function-corrected de Vacouleurs, Sérsic, de Vacouleurs+Exponential, and Sérsic+Exponential fits of ~7 × 105 galaxies presented in Meert et al. to include the g and i bands. Fits are analysed using the physically motivated flagging system presented in the original text, making adjustments for the differing signal to noise when necessary. We compare the fits in each of the g, r, and i bands. Fixed aperture magnitudes and colours are also provided for all galaxies. The catalogues are available in electronic format. [ABSTRACT FROM AUTHOR]

In this paper, we investigate the impact that realistic scale-dependent systematic effects may have on cosmic shear tomography. We model spatially varying residual galaxy ellipticity and galaxy size variations in weak lensing measurements and propagate these through to predicted changes in the uncertainty and bias of cosmological parameters. We show that the survey strategy -- whether it is regular or randomized -- is an important factor in determining the impact of a systematic effect: a purely randomized survey strategy produces the smallest biases, at the expense of larger parameter uncertainties, and a very regularized survey strategy produces large biases, but unaffected uncertainties. However, by removing, or modelling, the affected scales (l-modes) in the regular cases the biases are reduced to negligible levels. We find that the integral of the systematic power spectrum is not a good metric for dark energy performance, and we advocate that systematic effects should be modelled accurately in real space, where they enter the measurement process, and their effect subsequently propagated into power spectrum contributions. [ABSTRACT FROM AUTHOR]

We report the discovery of an extremely dense group of massive galaxies at the centre of the protocluster at z =3.09 in the SSA22 field from near-infrared spectroscopy conducted with the multi-object infrared camera and spectrograph (MOIRCS) on the Subaru Telecope. The newly discovered group comprises seven galaxies confirmed at zspec ≈3.09 within 180 kpc, including five massive objects with the stellarmasses larger than 1010.5 M☉ and is associated with a bright submillimetre source SSA22-AzTEC14. The dynamical mass of the group estimated from the line-of-sight velocity dispersion of the members is Mdyn ~ 1.6 ± 0.3 × 1013M☉. Such a dense group is expected to be very rare at high redshift, as we have found only a few comparable systems in large-volume cosmological simulations. Such rare groups in simulations are hosted in collapsed haloes with Mvir = 1013.4-1014.0M☉ and evolve into the brightest cluster galaxies (BCGs) of the most massive clusters at present. The observed AzTEC14 group at z = 3.09 is therefore very likely to be a proto-BCG in the multiple merger phase. The observed total stellar mass of the group is 5.8+5.1 -2.0 × 1011M☉, which suggests that over half the stellar mass of its descendant had been formed by z = 3. Moreover, we have identified over two members for each of the four Lyα blobs (LABs) using our new spectroscopic data. This verifies our previous argument that many of the LABs in the SSA22 protocluster associated with multiple developed stellar components. [ABSTRACT FROM AUTHOR]

PKS 2155-304 is one of the brightest extragalactic source in the X-ray and EUV bands, and is a prototype for the BL Lac class of objects. In this paper, we investigate the large-scale environment of this source using new multi-object as well as long-slit spectroscopy, together with archival spectra and optical images. We find clear evidence of a modest overdensity of galaxies at z = 0.116 10 ± 0.000 06, consistent with previous determinations of the BL Lac redshift. The galaxy group has a radial velocity dispersion of 250+80-40 km s-1 and a virial radius of 0.22 Mpc, yielding a role-of-thumb estimate of the virial mass of Mvir ~ 1.5 × 1013 M☉, i.e. one order of magnitude less than that observed in similar objects. This result hints towards a relatively wide diversity in the environmental properties of BL Lac objects. [ABSTRACT FROM AUTHOR]

Measurements are presented and analysed of the strength of the Ca II triplet lines in red giants in Galactic globular and open clusters, and in a sample of red giants in the LMC disc that have significantly different [Ca/Fe] abundance ratios to the Galactic objects. The Galactic objects are used to generate a calibration between Ca II triplet line strength and [Fe/H], which is then used to estimate [Fe/H]CaT for the LMC stars. The values are then compared with the [Fe/H]spec determinations from high-dispersion spectroscopy. After allowance for a small systematic offset, the two abundance determinations are in excellent agreement. Further, as found in earlier studies, the difference is only a very weak function of the [Ca/Fe] ratio. For example, changing [Ca/Fe] from +0.3 to -0.2 causes the Ca II-based abundance to underestimate [Fe/H]spec by only ~0.15 dex, assuming a Galactic calibration. Consequently, the Ca II triplet approach to metallicity determinations can be used without significant bias to study stellar systems that have substantially different chemical evolution histories. [ABSTRACT FROM AUTHOR]

We present long-term (months–years) X-ray spectral variability of the Seyfert 1.8 galaxy NGC 1365 as observed by Swift, which provides well-sampled observations over a much longer timescale (six years) and a much larger flux range than is afforded by other observatories. At very low luminosities, the spectrum is very soft, becoming rapidly harder as the luminosity increases and then, above a particular luminosity, softening again. At a given flux level, the scatter in hardness ratio is not very large, meaning that the spectral shape is largely determined by the luminosity. The spectra were therefore summed in luminosity bins and fitted with a variety of models. The best-fitting model consists of two power laws, one unabsorbed and another, more luminous, which is absorbed. In this model, we find a range of intrinsic 0.5–10.0 keV luminosities of approximately 1.1–3.5 erg s−1, and a very large range of absorbing columns, of approximately 1022–1024 cm−2. Interestingly, we find that the absorbing column decreases with increasing luminosity, but that this result is not due to changes in ionization. We suggest that these observations might be interpreted in terms of a wind model in which the launch radius varies as a function of ionizing flux and disc temperature and therefore moves out with increasing accretion rate, i.e. increasing X-ray luminosity. Thus, depending on the inclination angle of the disc relative to the observer, the absorbing column may decrease as the accretion rate goes up. The weaker, unabsorbed, component may be a scattered component from the wind. [ABSTRACT FROM AUTHOR]

We present the results of a study investigating the rest-frame ultraviolet (UV) spectral slopes of redshift z ≈ 5 Lyman-break galaxies (LBGs). By combining deep Hubble Space Telescope imaging of the Cosmic Assembly Near-infrared Deep Extragalactic Legacy Survey and Hubble Ultra-Deep Field with ground-based imaging from the UKIRT Infrared Deep Sky Survey Ultra Deep Survey, we have produced a large sample of z ≈ 5 LBGs spanning an unprecedented factor of >100 in UV luminosity. Based on this sample we find a clear colour–magnitude relation (CMR) at z ≈ 5, such that the rest-frame UV slopes (β) of brighter galaxies are notably redder than their fainter counterparts. We determine that the z ≈ 5 CMR is well described by a linear relationship of the form: dβ = (−0.12 ± 0.02)dMUV, with no clear evidence for a change in CMR slope at faint magnitudes (i.e. MUV ≥ −18.9). Using the results of detailed simulations we are able, for the first time, to infer the intrinsic (i.e. free from noise) variation of galaxy colours around the CMR at z ≈ 5. We find significant (12σ) evidence for intrinsic colour variation in the sample as a whole. Our results also demonstrate that the width of the intrinsic UV slope distribution of z ≈ 5 galaxies increases from Δβ ≃ 0.1 at MUV = −18 to Δβ ≃ 0.4 at MUV = −21. We suggest that the increasing width of the intrinsic galaxy colour distribution and the CMR itself are both plausibly explained by a luminosity-independent lower limit of β ≈ −2.1, combined with an increase in the fraction of red galaxies in brighter UV-luminosity bins. [ABSTRACT FROM AUTHOR]

This paper presents a new sample of BL Lac objects selected from a deep (30 mJy) radio survey of flat spectrum radio sources (the CLASS blazar survey). The sample is one of the largest well-defined samples in the low-power regime with a total of 130 sources of which 55 satisfy the ‘classical’ optical BL Lac selection criteria, and the rest have indistinguishable radio properties. The primary goal of this study is to establish the radio luminosity function (RLF) on firm statistical ground at low radio luminosities where previous samples have not been able to investigate. The gain of taking a peek at lower powers is the possibility to search for the flattening of the luminosity function which is a feature predicted by the beaming model but which has remained elusive to observational confirmation. In this study, we extend for the first time the BL Lac RLF down to very low radio powers ∼1022 W Hz−1, i.e. two orders of magnitude below the RLF currently available in the literature. In the process, we confirm the importance of adopting a broader, and more physically meaningful set of classification criteria to avoid the systematic missing of low-luminosity BL Lacs. Thanks to the good statistics we confirm the existence of weak but significant positive cosmological evolution for the BL Lac population, and we detect, for the first time the flattening of the RLF at L ∼ 1025 W Hz−1 in agreement with the predictions of the beaming model. [ABSTRACT FROM AUTHOR]

Using a method to discover and classify supernovae (SNe) in galaxy spectra, we find 90 Type Ia SNe (SNe Ia) and 10 Type II SNe among the ∼700 000 galaxy spectra in the Sloan Digital Sky Survey Data Release 7 that have star-formation histories (SFHs) derived with the VErsatile SPectral Analysis code (vespa). We use the SN Ia sample to measure SN Ia rates per unit stellar mass. We confirm, at the median redshift of the sample, z = 0.1, the inverse dependence on galaxy mass of the SN Ia rate per unit mass, previously reported by Li et al. for a local sample. We further confirm, following Kistler et al., that this relation can be explained by the combination of galaxy ‘downsizing’ and a power-law delay-time distribution (DTD; the distribution of times that elapse between a hypothetical burst of star formation and the subsequent SN Ia explosions) with an index of −1, inherent to the double-degenerate progenitor scenario. We use the method of Maoz et al. to recover the DTD by comparing the number of SNe Ia hosted by each galaxy in our sample with the vespa-derived SFH of the stellar population within the spectral aperture. In this galaxy sample, which is dominated by old and massive galaxies, we recover a ‘delayed’ component to the DTD of 4.5 ± 0.6 (statistical) ${_{-0.5}\!\!\!\!\!\!\!\!\!\!\!\!\!\!\!\!^{\rm +0.3}}$ (systematic) × 10− 14 SNe M⊙− 1 yr− 1 for delays in the range >2.4 Gyr. The mass-normalized SN Ia rate, averaged over all masses and redshifts in our galaxy sample, is $R_{{\rm Ia,M}}(z=0.1) = 0.10 \pm 0.01\ (\rm statistical) \pm 0.01\ (\rm systematic)\ {\rm SNuM}$, and the volumetric rate is RIa, V(z = 0.1) = 0.247 ${_{-0.026}\!\!\!\!\!\!\!\!\!\!\!\!\!\!\!\!\!\!\!\!\!\!\!^{\rm +0.029}}$ (statistical) ${_{-0.031}\!\!\!\!\!\!\!\!\!\!\!\!\!\!\!\!\!\!\!\!\!\!\!^{\rm +0.016}}$ (systematic) × 10− 4 SNe yr− 1 Mpc− 3. This rate is consistent with the rates and rate evolution from other recent SN Ia surveys, which together also indicate a ∼t−1 DTD. [ABSTRACT FROM AUTHOR]

We analyse the properties of dark matter haloes in the cold-plus-warm dark matter (CWDM) cosmologies. We study their dependence on the fraction and velocity dispersion of the warm particle, keeping the free-streaming scale fixed. To this end, we consider three models with the same free-streaming: (1) a mixture of 90 per cent of CDM and 10 per cent of WDM with the mass 1 keV; (2) a mixture of 50 per cent of CDM and 50 per cent of WDM with the mass 5 keV and (3) pure WDM with the mass 10 keV. 'Warm' particles have rescaled -Dirac spectrum of primordial velocities (as non-resonantly produced sterile neutrinos would have). We compare the properties of haloes among these models and with a ...CDM with the same cosmological parameters. We demonstrate that although these models have the same free-streaming length and the suppression of matter spectra are similar at scales probed by the Lyman a forest (comoving wave-numbers k < 3-5 h Mpc-1), the resulting properties of haloes with masses below ~1011M⊙are different due to the different behaviour of matter power spectra at smaller scales. In particular, we find that while the number of galaxies remains the same as in the ...CDM case, their density profiles become much less concentrated and hence in better agreement with current observational constraints. Our results imply that a single parameter (e.g. free-streaming length) description of these models is not enough to fully capture their effects on the structure formation process. [ABSTRACT FROM AUTHOR]

We present a spectrophotometric survey of 2522 extragalactic globular clusters (GCs) around 12 early-type galaxies, nine of which have not been published previously. Combining spacebased and multicolour wide-field ground-based imaging, with spectra from the Keck/DEep Imaging Multi-Object Spectrograph (DEIMOS) instrument, we obtain an average of 160 GC radial velocities per galaxy, with a high-velocity precision of ~15 km s-1 per GC. After studying the photometric properties of the GC systems, such as their spatial and colour distributions, we focus on the kinematics of metal-poor (blue) and metal-rich (red) GC subpopulations to an average distance of ~8 effective radii from the galaxy centre. Our results show that for some systems the bimodality in GC colour is also present in GC kinematics. The kinematics of the red GC subpopulations are strongly coupled with the host galaxy stellar kinematics. The blue GC subpopulations are more dominated by random motions, especially in the outer regions, and decoupled from the red GCs. Peculiar GC kinematic profiles are seen in some galaxies: the blue GCs in NGC 821 rotate along the galaxy minor axis, whereas the GC system of the lenticular galaxy NGC 7457 appears to be strongly rotation supported in the outer region. We supplement our galaxy sample with data from the literature and carry out a number of tests to study the kinematic differences between the two GC subpopulations. We confirm that the GC kinematics are coupled with the host galaxy properties and find that the velocity kurtosis and the slope of their velocity dispersion profiles are different between the two GC subpopulations in more massive galaxies. [ABSTRACT FROM AUTHOR]

ABSTRACT Strong gravitational lensing magnifies the flux from distant galaxies, allowing us to detect emission lines that would otherwise fall below the detection threshold for medium-resolution spectroscopy. Here we present the detection of temperature-sensitive oxygen emission lines from three galaxies at 2 ≲ z ≲ 3.5, which enables us to directly determine the oxygen abundances and thereby double the number of galaxies at z > 2 for which this has been possible. The three galaxies have ∼10 per cent solar oxygen abundances in agreement with strong emission-line diagnostics. Carbon and nitrogen ratios relative to oxygen are subsolar as expected for young metal-poor galaxies. Two of the galaxies are Lyman α (Lyα) emitters with rest-frame equivalent widths of 20 and 40 Å, respectively, and their high magnification factors allow us for the first time to gain insight into the physical characteristics of high-redshift Lyα emitters. Using constraints from the physical properties of the galaxies, we accurately reproduce their line profiles with radiative transfer models. The models show a relatively small outflow in agreement with the observed small velocity offsets between nebular emission and interstellar absorption lines. [ABSTRACT FROM AUTHOR]

ABSTRACT We construct Tully-Fisher relationships (TFRs) in the u, g, r, i and z bands and stellar mass TFRs for a sample of 25 698 late spiral-type galaxies (with 0.045 < z < 0.085) from the Sloan Digital Sky Survey (SDSS) and study the effects of environment on the relation. We use SDSS-measured Balmer emission line widths, vFWHM, as a proxy for disc circular velocity, vcirc. A priori, it is not clear whether we can construct accurate TFRs given the small 3 arcsec diameter of the fibres used for SDSS spectroscopic measurements. However, we show by modelling the Hα emission profile as observed through a 3 arcsec aperture that for galaxies at appropriate redshifts ( z > 0.045) the fibres sample enough of the disc to obtain a linear relationship between vFWHM and vcirc, allowing us to obtain a TFR and to investigate dependence on other variables. We also develop a methodology for distinguishing between astrophysical and sample bias in the fibre TFR trends. We observe the well-known steepening of the TFR in redder bands in our sample. We divide the sample of galaxies into four equal groups using projected neighbour density (Σ) quartiles and find no significant dependence on environment, extending previous work to a wider range of environments and a much larger sample. Having demonstrated that we can construct SDSS-based TFRs is very useful for future TFR studies because of the large sample size available in the SDSS. [ABSTRACT FROM AUTHOR]