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We present an estimate of the bulk flow in a volume of radii 150−200 h−1 Mpc using the minimum variance method with data from the CosmicFlows-4 (CF4) catalogue. The addition of new data in the CF4 has resulted in an increase in the estimate of the bulk flow in a sphere of radius 150 h−1 Mpc relative to the CosmicFlows-3 (CF3). This bulk flow has an |$\sim 0.015~{{\ \rm per\ cent}}$| chance of occurring in the standard cosmological model with cosmic microwave background derived parameters. Given that the CF4 is deeper than the CF3, we were able to use the CF4 to accurately estimate the bulk flow on scales of 200 h−1 Mpc (equivalent to 266 Mpc for Hubble constant H 0 = 75 km s−1 Mpc−1) for the first time. This bulk flow is in even greater tension with the standard model, having |$\sim 1.5\times 10^{-4}\ \%$| probability of occurring. To estimate the bulk flow accurately, we introduce a novel method to calculate distances and velocities from distance moduli that is unbiased and accurate at all distances. Our results are completely independent of the value of H 0. [ABSTRACT FROM AUTHOR]

While the sample of optical Type Ia supernova (SN Ia) light curves (LCs) usable for cosmological parameter measurements surpasses 2000, the sample of published, cosmologically viable near-infrared (NIR) SN Ia LCs, which have been shown to be good 'standard candles,' is still ≲ 200. Here, we present high-quality NIR LCs for 83 SNe Ia ranging from 0.002 < z < 0.09 as a part of the Dark Energy, H0, and peculiar Velocities using Infrared Light from Supernovae (DEHVILS) survey. Observations are taken using UKIRT's WFCAM, where the median depth of the images is 20.7, 20.1, and 19.3 mag (Vega) for Y, J , and H -bands, respectively. The median number of epochs per SN Ia is 18 for all three bands (Y,J , and H) combined and 6 for each band individually. We fit 47 SN Ia LCs that pass strict quality cuts using three LC models, SALT3, snoopy , and B  aye SN and find scatter on the Hubble diagram to be comparable to or better than scatter from optical-only fits in the literature. Fitting NIR-only LCs, we obtain standard deviations ranging from 0.128 to 0.135 mag. Additionally, we present a refined calibration method for transforming 2MASS magnitudes to WFCAM magnitudes using HST CALSPEC stars that results in a 0.03 mag shift in the WFCAM Y -band magnitudes. [ABSTRACT FROM AUTHOR]

How the cosmic web feeds haloes, and fuels galaxy formation is an open question with wide implications. This study explores the mass assembly in the Local Group (LG) within the context of the local cosmography by employing simulations whose initial conditions have been constrained to reproduce the local environment. The goal of this study is to inspect whether the direction of accretion of satellites on to the Milky Way and Andromeda galaxies is related to the cosmic web. The analysis considers the three high-resolution simulations available in the HESTIA simulation suite, as well as the derived velocity shear and tidal tensors. We notice two eras in the LG accretion history, delimited by an epoch around z ≈ 0.7. We also find that satellites can travel up to ∼4 Mpc, relative to their parent halo before crossing its viral radius R 200. Finally, we observe a strong alignment of the infall direction with the axis of slowest collapse |$\boldsymbol{e}_{3}$| of both tidal and shear tensors, implying satellites of the LG originated from one particular region of the cosmic web and were channeled towards us via the process of accretion.This alignment is dominated by the satellites that enter during the early infall era, i.e. z > 0.7. [ABSTRACT FROM AUTHOR]

We present a new catalogue of distances and peculiar velocities (PVs) of 34 059 early-type galaxies derived from fundamental plane (FP) measurements using data from the Sloan Digital Sky Survey (SDSS). This |$7016\, \mathrm{deg}^{2}$| homogeneous sample comprises the largest set of PVs produced to date and extends the reach of PV surveys up to a redshift limit of z  = 0.1. Our SDSS-based FP distance measurements have a mean uncertainty of 23 per cent. Alongside the data, we produce an ensemble of 2048 mock galaxy catalogues that reproduce the data selection function, and are used to validate our fitting pipelines and check for systematic errors. We uncover a significant trend between group richness and mean surface brightness within the sample, which may hint at an environmental dependence within the FP or the presence of unresolved systematics, and can result in biased PVs. This is removed by using multiple FP fits as function of group richness, a procedure made tractable through a new analytic derivation for the integral of a three-dimensional (3D) Gaussian over non-trivial limits. Our catalogue is calibrated to the zero-point of the CosmicFlows-III sample with an uncertainty of 0.004 dex (not including cosmic variance or the error within CosmicFlows-III itself), which is validated using independent cross-checks with the predicted zero-point from the 2M++ reconstruction of our local velocity field. Finally, as an example of what is possible with our new catalogue, we obtain preliminary bulk flow measurements up to a depth of |$135\,{\rm h}^{-1}\mathrm{Mpc}$|⁠. We find a slightly larger-than-expected bulk flow at high redshift, although this could be caused by the presence of the Shapley supercluster, which lies outside the SDSS PV footprint. [ABSTRACT FROM AUTHOR]

The 'Spectroscopy and H -band Imaging of Virgo cluster galaxies' (SHIVir) survey is an optical and near-infrared survey which combines SDSS photometry, deep H -band photometry, and long-slit optical spectroscopy for 190 Virgo cluster galaxies covering all morphological types over the stellar mass range log (M */M⊙) = 7.8–11.5. We present the spectroscopic sample selection, data reduction, and analysis for this SHIVir sample. We have used and optimized the pPXF routine to extract stellar kinematics from our data. Ultimately, resolved kinematic profiles (rotation curves and velocity dispersion profiles) are available for 133 SHIVir galaxies. A comprehensive data base of photometric and kinematic parameters for the SHIVir sample is presented with grizH magnitudes, effective surface brightnesses, effective and isophotal radii, rotational velocities, velocity dispersions, and stellar and dynamical masses. Parameter distributions highlight some bimodal distributions and possible sample biases. A qualitative study of resolved extended velocity dispersion profiles suggests a link between the so-called 'sigma-drop' kinematic profile and the presence of rings in lenticular S0 galaxies. Rising dispersion profiles are linked to early-type spirals or dwarf ellipticals for which a rotational component is significant, whereas peaked profiles are tied to featureless giant ellipticals. [ABSTRACT FROM AUTHOR]

Surveys of galaxy distances and radial peculiar velocities can be used to reconstruct the large-scale structure. Other than systematic errors in the zero-point calibration of the galaxy distances the main source of uncertainties of such data is errors on the distance moduli, assumed here to be Gaussian and thus turning into lognormal errors on distances and velocities. Naively treated, this leads to spurious nearby outflow and strong infall at larger distances. The lognormal bias is corrected here and tested against mock data extracted from a ΛCDM simulation, designed to statistically follow the grouped Cosmicflows-3 (CF3) data. Considering a subsample of data points, all of which have the same true distances or the same redshifts, the lognormal bias arises because the means of the distributions of observed distances and velocities are skewed off the means of the true distances and velocities. However, the medians are invariant under the lognormal transformation. This invariance allows the Gaussianization of the distances and velocities and the removal of the lognormal bias. This bias Gaussianization correction (BGc) algorithm is tested against mock CF3 catalogues. The test consists of a comparison of the BGc estimated with the simulated distances and velocities and of an examination of the Wiener filter reconstruction from the BGc data. Indeed, the BGc eliminates the lognormal bias. The estimation of Hubble's constant (H 0) is also tested. The residual of the BGc-estimated H 0 from the simulated values is |$-0.6\pm 0.7{\, \rm km \ s^{-1}\, Mpc^{-1}}$|⁠ , and is dominated by the cosmic variance. The BGc correction of the actual CF3 data yields |$H_0=75.8\pm 1.1{\, \rm km \ s^{-1}\, Mpc^{-1}}$|⁠. [ABSTRACT FROM AUTHOR]

We present the hestia simulation suite: High-resolutions Environmental Simulations of The Immediate Area, a set of cosmological simulations of the Local Group. Initial conditions constrained by the observed peculiar velocity of nearby galaxies are employed to accurately simulate the local cosmography. Halo pairs that resemble the Local Group are found in low resolutions constrained, dark matter only simulations, and selected for higher resolution magneto hydrodynamic simulation using the arepo code. Baryonic physics follows the auriga model of galaxy formation. The simulations contain a high-resolution region of 3–5 Mpc in radius from the Local Group mid-point embedded in the correct cosmographic landscape. Within this region, a simulated Local Group consisting of a Milky Way and Andromeda like galaxy forms, whose description is in excellent agreement with observations. The simulated Local Group galaxies resemble the Milky Way and Andromeda in terms of their halo mass, mass ratio, stellar disc mass, morphology separation, relative velocity, rotation curves, bulge-disc morphology, satellite galaxy stellar mass function, satellite radial distribution, and in some cases, the presence of a Magellanic cloud like object. Because these simulations properly model the Local Group in their cosmographic context, they provide a testing ground for questions where environment is thought to play an important role. [ABSTRACT FROM AUTHOR]

The goodness-of-fit (GoF) of the Cosmicflows-2 (CF2) data base of peculiar velocities with the Λ cold dark matter (ΛCDM) standard model of cosmology is presented. Standard application of the X2 statistics of the full data base, of its 4838 data points, is hampered by the small-scale non-linear dynamics which is not accounted for by the (linear regime) velocity power spectrum. The bulk velocity constitutes a highly compressed representation of the data which filters out the small-scales non-linear modes. Hence the statistics of the bulk flowprovides an efficient tool for assessing the GoF of the data given a model. The particular approach introduced here is to use the (spherical top-hat window) bulk velocity extracted from theWiener filter reconstruction of the 3D velocity field as a linear low-pass filtered highly compressed representation of the CF2 data. An ensemble 2250 random linear realizations of the Wilkinson Microwave Anisotropy Probe (WMAP)/ΛCDM model has been used to calculate the bulk velocity autocovariance matrix. We find that the CF2 data is consistent with the WMAP/ΛCDM model to better than the 2σ confidence limits. This provides a further validation that the CF2 data base is consistent with the standard model of cosmology. [ABSTRACT FROM AUTHOR]

Near-field cosmology is practised by studying the Local Group (LG) and its neighbourhood. This paper describes a framework for simulating the 'near field' on the computer. Assuming the Λ cold dark matter (ΛCDM) model as a prior and applying the Bayesian tools of the Wiener filter and constrained realizations of Gaussian fields to the Cosmicflows-2 (CF2) survey of peculiar velocities, constrained simulations of our cosmic environment are performed. The aim of these simulations is to reproduce the LG and its local environment. Our main result is that the LG is likely a robust outcome of the ΛCDMscenario when subjected to the constraint derived from CF2 data, emerging in an environment akin to the observed one. Three levels of criteria are used to define the simulated LGs. At the base level, pairs of haloes must obey specific isolation, mass and separation criteria. At the second level, the orbital angular momentum and energy are constrained, and on the third one the phase of the orbit is constrained. Out of the 300 constrained simulations, 146 LGs obey the first set of criteria, 51 the second and 6 the third. The robustness of our LG 'factory' enables the construction of a large ensemble of simulated LGs. Suitable candidates for high-resolution hydrodynamical simulations of the LG can be drawn from this ensemble, which can be used to perform comprehensive studies of the formation of the LG. [ABSTRACT FROM AUTHOR]

This paper combines observational data sets and cosmological simulations to generate realistic numerical replicas of the nearby Universe. The latter are excellent laboratories for studies of the non-linear process of structure formation in our neighbourhood. With measurements of radial peculiar velocities in the local Universe (cosmicflows-2) and a newly developed technique, we produce Constrained Local UniversE Simulations (CLUES). To assess the quality of these constrained simulations, we compare them with random simulations as well as with local observations. The cosmic variance, defined as the mean one-sigma scatter of cell-to-cell comparison between two fields, is significantly smaller for the constrained simulations than for the random simulations. Within the inner part of the box where most of the constraints are, the scatter is smaller by a factor of 2 to 3 on a 5 h-1 Mpc scale with respect to that found for random simulations. This one-sigma scatter obtained when comparing the simulated and the observation-reconstructed velocity fields is only 104 ± 4 km s-1, i.e. the linear theory threshold. These two results demonstrate that these simulations are in agreement with each other and with the observations of our neighbourhood. For the first time, simulations constrained with observational radial peculiar velocities resemble the local Universe up to a distance of 150 h-1 Mpc on a scale of a few tens of megaparsecs. When focusing on the inner part of the box, the resemblance with our cosmic neighbourhood extends to a few megaparsecs (<5 h-1 Mpc). The simulations provide a proper large-scale environment for studies of the formation of nearby objects. [ABSTRACT FROM AUTHOR]

Recent observational studies have demonstrated that the majority of satellite galaxies tend to orbit their hosts on highly flattened, vast, possibly corotating planes. Two nearly parallel planes of satellites have been confirmed around the M31 galaxy and around the Centaurus A galaxy, while the Milky Way also sports a plane of satellites. It has been argued that such an alignment of satellites on vast planes is unexpected in the standard Λ cold dark matter (ΛCDM) model of cosmology if not even in contradiction to its generic predictions. Guided by ΛCDM numerical simulations, which suggest that satellites are channelled towards hosts along the axis of the slowest collapse as dictated by the ambient velocity shear tensor, we re-examine the planes of local satellites systems within the framework of the local shear tensor derived from the Cosmicflows-2 data set. The analysis reveals that the Local Group and Centaurus A reside in a filament stretched by the Virgo cluster and compressed by the expansion of the Local Void. Four out of five thin planes of satellite galaxies are indeed closely aligned with the axis of compression induced by the Local Void. Being the less massive system, the moderate misalignment of the Milky Way's satellite plane can likely be ascribed to its greater susceptibility to tidal torques, as suggested by numerical simulations. The alignment of satellite systems in the local Universe with the ambient shear field is thus in general agreement with predictions of the ΛCDM model. [ABSTRACT FROM AUTHOR]

Full sky surveys of peculiar velocity are arguably the best way to map the large-scale structure (LSS) out to distances of a few Õ 100 h-1 Mpc. Using the largest and most accurate ever catalogue of galaxy peculiar velocities Cosmicflows-2, the LSS has been reconstructed by means of the Wiener filter (WF) and constrained realizations (CRs) assuming as a Bayesian prior model the A cold dark matter model with the WMAP inferred cosmological parameters. This paper focuses on studying the bulk flow of the local flow field, defined as the mean velocity of top-hat spheres with radii ranging out to R = 500 h-1 Mpc. The estimated LSS, in general, and the bulk flow, in particular, are determined by the tension between the observational data and the assumed prior model. A pre-requisite for such an analysis is the requirement that the estimated bulk flow is consistent with the prior model. Such a consistency is found here. At R = 50 (150) h-1 Mpc, the estimated bulk velocity is 250 ± 21 (239 ± 38) km s-1. The corresponding cosmic variance at these radii is 126 (60) km s-1, which implies that these estimated bulk flows are dominated by the data and not by the assumed prior model. The estimated bulk velocity is dominated by the data out to R ≈ 200 h-1 Mpc, where the cosmic variance on the individual supergalactic Cartesian components (of the rms values) exceeds the variance of the CRs by at least a factor of 2. The SGX and SGY components of the cosmic microwave background dipole velocity are recovered by the WF velocity field down to a very few km s-1. The SGZ component of the estimated velocity, the one that is most affected by the zone of avoidance, is off by 126 km s-1 (an almost 2σ discrepancy). The bulk velocity analysis reported here is virtually unaffected by the Malmquist bias and very similar results are obtained for the data with and without the bias correction. [ABSTRACT FROM AUTHOR]

Cosmic Flows is an international multi-element project with the goal to map motions of galaxies in the local Universe. Kinematic information from observations in the radio H I line and photometry at optical or near-infrared bands are acquired to derive the large majority of distances that are obtained through the luminosity-linewidth or Tully-Fisher relation. This paper gathers additional observational radio data, frequently unpublished, retrieved from the archives of Green Bank, Parkes and Arecibo telescopes. Extracted HI profiles are consistently processed to produce linewidth measurements. Our current 'All-Digital HI Catalog' contains a total of 20 343 H I spectra for 17 738 galaxies with 14 802 galaxies with accurate linewidth measurement useful for Tully-Fisher galaxy distances. This addition of 4117 new measurements represents an augmentation of 34 per cent compared to our last release. [ABSTRACT FROM AUTHOR]

ABSTRACT We present the results from a search for H i emission from a sample of newly discovered dwarf galaxies in the M81 group. H i is detected in three galaxies, all of which are classified as blue compact dwarf galaxies (BCDs). The H i masses of these galaxies are ∼106 M⊙, making them some of the lowest mass BCDs known. For these three galaxies far-ultraviolet (FUV) images (from GALEX) and Hα images (from the Russian 6 m BTA telescope) are available. The Hα emission is very faint and, in principle, could be produced by a single O star. Further, in all cases we find offsets between the peak of the FUV emission and that of the Hα emission. Offsets between the most recent sites of star formation (i.e. those traced by Hα) and the older sites (i.e. those traced by FUV) would be natural if the star formation is stochastic. In spite of the expectation that the effects of mechanical feedback from star formation would most directly be seen in the smallest galaxies with low gravitational potentials, we only see tentative evidence of outflowing H i gas associated with the star-forming region in one of the galaxies. [ABSTRACT FROM AUTHOR]

BSTRACT Within the 'Cosmic Flows' project, I-band photometry of 524 relatively nearby galaxies has been carried out over the course of several years with the University of Hawaii 2.2-m telescope and a camera with a 7.5-arcmin field of view. The primary scientific goal was to provide global magnitudes and inclinations for galaxies for the purpose of measuring distances through the correlation between galaxy luminosities and rotation rates. The 1σ accuracy on a total magnitude is 0.08 mag. The observations typically extend to 7-8 exponential disc scalelengths, so the data are useful for studies of the structural properties of galaxies. [ABSTRACT FROM AUTHOR]

The neutral hydrogen properties of 1822 galaxies are being studied with the Green Bank 100-m and the Parkes 64-m telescopes as part of the 'Cosmic Flows' programme. Observed parameters include systemic velocities, profile linewidths and integrated fluxes. The linewidth information can be combined with the optical and infrared photometry to obtain distances. The 1822 H observations complement an inventory of archives. All told, H linewidth information is available for almost all of five samples: (i) luminosity-linewidth correlation calibrators; (ii) zero-point calibrators for the Type Ia supernova scale; (iii) a dense local sample of spiral galaxies with within 3000 km s; (iv) a sparser sample of 60-μm selected galaxies within 6000 km s that provides an all-sky coverage of our extended supercluster complex; and (v) an even sparser sample of flat galaxies, extreme edge-on spirals, extending in a volume out to 12 000 km s. The H information for 13 941 galaxies, whether from the archives or acquired as part of the Cosmic Flows observational programme, is uniformly re-measured and made available through the Extragalactic Distance Database website. [ABSTRACT FROM AUTHOR]

We present and -, -, -, - and H-band surface brightness profiles and bulge-disc decompositions for a morphologically broad sample of 286 Virgo Cluster Catalogue (VCC) galaxies. The H-band data come from a variety of sources including our survey of 171 VCC galaxies at the University of Hawaii (UH) 2.2-m telescope, Canada-France-Hawaii Telescope (CFHT) and United Kingdom Infrared Telescope (UKIRT), and another 115 galaxies from the Two Micron All Sky Survey (2MASS) and GOLDMine archives. The optical data for all 286 VCC galaxies were extracted from the Sloan Digital Sky Survey (SDSS) images. The H-band and the SDSS data were analysed in a homogeneous manner using our own software, yielding a consistent set of deep, multiband surface brightness profiles for each galaxy. Average surface brightness profiles per morphological bin were created in order to characterize the variety of galaxy light profiles across the Hubble sequence. The 1D bulge-disc decomposition parameters, as well as non-parametric galaxy measures, such as effective radius, effective surface brightness and light concentration, are presented for all 286 VCC galaxies in each of the five optical/near-infrared wavebands. The profile decompositions account for bulge and disc components, spiral arms, nucleus and atmospheric blurring. The Virgo spiral galaxy bulges typically have a Sérsic index , while elliptical galaxies prefer . No galaxy spheroid requires . The light profiles for 70 per cent of the Virgo elliptical galaxies reveal the presence of both a spheroid and disc component. A more in-depth discussion of the structural parameter trends can be found in McDonald, Courteau & Tully. The data provided here should serve as a base for studies of galaxy structure and stellar populations in the cluster environment. The galaxy light profiles and bulge-disc decomposition results are available at the Centre de Données astronomiques de Strasbourg (CDS; ) and the author's own website (). [ABSTRACT FROM AUTHOR]

We present a compilation of galaxies in the NGC 1023 Group, an accumulation of late-type galaxies at a distance of 10 Mpc. Members at high and intermediate luminosities were identified from their spectroscopic velocities. Members at low luminosities were identified from their morphologies on wide-field CCD images. The faint-end slope is in the range . There is evidence for two dwarf galaxy populations: one in the halo of NGC 1023 that is dominated by dwarf elliptical galaxies, and one in the infall region surrounding NGC 1023 that contains mainly dwarf irregular galaxies. Similar distinctive populations are observed in the Local Group. Through our imaging surveys, a picture has emerged of the distributions and types of dwarf galaxies over a wide range of environments. Of greatest interest is a correlation between dwarf galaxy population and parent halo mass. The number of dwarfs per unit mass is constant over the range of halo masses . There are small but significant variations in luminosity functions with location. These variations can be attributed to differences in the bright and intermediate luminosity populations. In less evolved regions marked by substantial populations of spirals, galaxies with intermediate luminosity are relatively common, and such regions have low mass-to-light ratios. In more evolved regions where spirals are absent, there is relative depletion at intermediate luminosities and, overall in such places, mass-to-light ratios are high. Statistics are still poor for regions outside of massive haloes but the faint-end slope of the luminosity function is comparable in the field with what is found in the massive haloes. Everywhere that has been studied, the faint-end slope is unequivocally shallower than the slope at low masses anticipated by hierarchical clustering theory. Though the slope is shallow, there is no hint of a cut-off down to an observational limit of . [ABSTRACT FROM AUTHOR]

We have acquired deep, H-band imaging for a sample of 286 Virgo cluster galaxies with mag and extracted surface photometry from optical Sloan Digital Sky Survey images of 742 Virgo Cluster Catalogue galaxies, including those with H-band images. We confirm the detection of a dip in the luminosity function indicative of a discontinuity in the cluster galaxy population; the dip is more pronounced at redder wavelengths. We find, in agreement with earlier works of Tully and Verheijen and ours for Ursa Major cluster galaxies, a clear dichotomy between high and low surface brightness (HSB and LSB) galaxy discs. The difference between the low and high brightness peaks of Virgo disc galaxies is ∼2 H-mag arcsec−2, significantly larger than any systematic errors. The high surface brightness disc galaxies have two distinct classes of high and low concentration bulges, while LSB galaxies have only low concentration bulges. Early-type galaxies exhibit a similar structural bimodality though offset from that of the spiral galaxies towards higher surface brightnesses. Both the early- and late-type structural bimodalities are uncorrelated with colour or any other structural parameter except, possibly, circular velocity. Random realizations of realistic surface brightness profiles suggest that a bimodal distribution of effective surface brightness is unexpected based on normal distributions of bulge and disc parameters. Rather, the structural bimodality may be linked to dynamic properties of galaxies. Low angular momentum systems may collapse to form dynamically important discs with high surface brightness, while high angular momentum systems would end up as low surface brightness galaxies dominated by the dark halo at all radii. The confirmation of structural bimodality for gas-rich and gas-poor galaxies in the high-density Virgo cluster as well as the low-density UMa cluster suggests that this phenomenon is independent of environment. [ABSTRACT FROM AUTHOR]

We present bulge and disc (B/D) decompositions of existing surface brightness profiles for 65 Ursa Major (UMa) cluster spiral galaxies. This improves upon the disc-only fits of Tully et al. The 1996 disc fits were used by Tully & Verheijen for their discovery of the bimodality of structural parameters in the UMa cluster galaxies. It is shown that our new one-dimensional B/D decompositions yield disc structural parameters that differ only slightly from the basic fits of Tully et al. and evidence for structural bimodality of UMa galaxies is maintained. Our B/D software for the decomposition of one-dimensional surface brightness profiles of galaxies uses a non-linear minimization scheme to recover the best-fitting Sérsic bulge and the exponential disc while accounting for the possible presence of a compact nucleus and spiral arms and for the effects of seeing and disc truncations. In agreement with Tully & Verheijen, we find that the distribution of near-infrared disc central surface brightnesses is bimodal with an F-test confidence of 80 per cent. There is also strong evidence for a local minimum in the luminosity function at . A connection between the brightness bimodality and a dynamical bimodality, based on new H i linewidths, is identified. The B/D parameters are presented in Table 1 . [ABSTRACT FROM AUTHOR]

We present surface photometry and metallicity measurements for 104 nearby dwarf galaxies imaged with the Advanced Camera for Surveys and Wide Field and Planetary Camera 2 aboard the Hubble Space Telescope. In addition, we carried out photometry for 26 galaxies of the sample and for Sextans B on images of the Sloan Digital Sky Survey. Our sample comprises dwarf spheroidal, irregular and transition type galaxies located within ∼10 Mpc in the field and in nearby groups: M81, Centaurus A, Sculptor and Canes Venatici I cloud. It is found that the early-type galaxies have on average higher metallicity at a given luminosity in comparison to the late-type objects. Dwarf galaxies with M B≥−12 to −13 mag deviate towards larger scalelengths from the scalelength–luminosity relation common for spiral galaxies, h∝ L0.5 B. The following correlations between fundamental parameters of the galaxies are consistent with expectations if there is pronounced gas loss through galactic winds: (1) between the luminosity of early-type dwarf galaxies and the mean metallicity of constituent red giant branch stars, Z∼ L0.4, (2) between mean surface brightness within the 25 mag arcsec−2 isophote and the corresponding absolute magnitude in the V and I bands, SB 25∼ 0.3 M25 and (3) between the central surface brightness (or effective surface brightness) and integrated absolute magnitude of galaxies in the V and I bands, SB0∼ 0.5 ML, SB e∼ 0.5 Me. The knowledge of basic photometric parameters for a large sample of dwarf galaxies is essential for a better understanding of their evolution. [ABSTRACT FROM AUTHOR]

The NGC 1407 Group stands out among nearby structures by its properties that suggest it is massive and evolved. It shares properties with entities that have been called fossil groups: the 1.4 m differential between the dominant elliptical galaxy and the second brightest galaxy comes close to satisfying the definition that has been used to define the fossil class. There are few intermediate-luminosity galaxies, but a large number of dwarfs in the group. We estimate there are 250 group members to the depth of our survey. The slope of the faint end of the luminosity function (reaching ) is . Velocities for 35 galaxies demonstrate that this group with one dominant galaxy has a mass of and . Two galaxies in close proximity to NGC 1407 have very large blueshifts. The most notable is the second brightest galaxy, NGC 1400, with a velocity of −1072 km s−1 with respect to the group mean. We report the detection of X-ray emission from this galaxy and from the group. [ABSTRACT FROM AUTHOR]

Abstract We present and discuss optical measurements of the faint end of the galaxy luminosity function down to M[sub R]=-10 in five different local environments of varying galaxy density and morphological content. The environments we studied, in order of decreasing galaxy density, are the Virgo Cluster, the NGC 1407 Group, the Coma I Group, the Leo Group and the NGC 1023 Group. Our results come from a deep wide-angle survey with the National Astronomical Observatories of Japan Subaru 8-m Telescope on Mauna Kea and are sensitive down to very faint surface-brightness levels. Galaxies were identified as group or cluster members on the basis of their surface brightness and morphology. The faintest galaxies in our sample have R∼ 22.5 . There were thousands of fainter galaxies but we cannot distinguish cluster members from background galaxies at these faint limits so do not attempt to determine a luminosity function fainter than M[sub R]=-1010 . In all cases, there are far fewer dwarfs than the numbers of low-mass haloes anticipated by cold dark matter theory. The mean logarithmic slope of the luminosity function between M[sub R]=-1018 and M[sub R]=-1010 is α≃-1.2 , far shallower than the cold dark matter mass function slope of α≃-1.8 . We would therefore need to be missing about 90 per cent of the dwarfs at the faint end of our sample in all the environments we study to achieve consistency with CDM theory. It is unlikely that such large numbers of dwarfs are missed because (i) the data are deep enough that we are sensitive to very low surface brightness galaxies, and (ii) the seeing is good enough that we can have some confidence in our ability to distinguish high surface brightness dwarfs from background galaxies brighter than R= 22.5 . One caveat is that we miss compact members taken to be background galaxies, but such objects (like M32) are thought to be rare. [ABSTRACT FROM AUTHOR]

We present and discuss optical, near-infrared and H imeasurements of the galaxy Markarian 1460 at a distance of 19 Mpc in the Ursa Major Cluster. This low-luminosity (M[sub B]=-14) galaxy is unusual because (i) it is blue (B-R=0.8) and has the spectrum of an H iigalaxy, (ii) it has a light profile that is smooth and well fitted by an r[sup 1/4] and not an exponential function at all radii larger than the seeing, and (iii) it has an observed central brightness of about μ[sub B]=20 mag arcsec[sup -2], intermediate between those of elliptical galaxies (on the bright μ[sub B] side) and normal low-luminosity dwarf irregular (on the low μ[sub B] side) galaxies. No other known galaxy exhibits all these properties in conjunction. On morphological grounds this galaxy looks like a normal distant luminous elliptical galaxy, since the Fundamental Plane tells us that higher luminosity normal elliptical galaxies tend to have lower surface-brightnesses. Markarian 1460 has 2×10[sup 7] M[sub ⊙] of H iand a ratio M(H i)/L[sub B] of 0.2, which is low compared to the typical values for star-forming dwarf galaxies. From the high surface-brightness and r[sup 1/4] profile, we infer that the baryonic component of Markarian 1460 has become self-gravitating through dissipative processes. From the colours, radio continuum, H iand optical emission line properties, and yet smooth texture, we infer that Markarian 1460 has had significant star formation as recently as ∼1 Gyr ago but not today. [ABSTRACT FROM AUTHOR]