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ABSTRACT The spectroscopic binarity of the Cepheid variable HV914 in the Large Magellanic Cloud is identified from published radial velocity observational data. The list of known binaries among Cepheid-type variable stars in the Magellanic Clouds is published in tabular form. The census indicates a serious deficiency of Cepheids with known companions compared with their Galactic counterparts; the implications of this are also discussed. A particular amplitude ratio ( [ABSTRACT FROM AUTHOR]

ABSTRACT We present new, accurate positions, spectral classifications, radial and rotational velocities, Hα fluxes, equivalent widths and B, V, I, R magnitudes for 579 hot emission-line stars (classes B0-F9) in the Large Magellanic Cloud (LMC) which include 469 new discoveries. Candidate emission-line stars were discovered using a deep, high-resolution Hα map of the central 25 degree2 of the LMC obtained by median stacking a dozen 2 h Hα exposures taken with the UK Schmidt Telescope (UKST). Spectroscopic follow-up observations on the Anglo-Australian Telescope, the UKST, the Very Large Telescope, the South African Astronomical Observatory 1.9 m and the 2.3-m telescope at Siding Spring Observatory have established the identity of these faint sources down to magnitude Requiv ∼ 23 for Hα (4.5 × 10−17 ergs cm−2 s−1 Å−1). Confirmed emission-line stars have been assigned an underlying spectral classification through cross-correlation against 131 absorption line template spectra covering the range O1-F8. We confirm 111 previously identified emission-line stars and 64 previously known variable stars with spectral types hotter than F8. The majority of hot stars identified (518 stars or 89 per cent) are of class B. Of all the hot emission-line stars in classes B-F, 130 or 22 per cent are type B[e], characterized by the presence of forbidden emission lines such as [S ii], [N ii] and [O ii]. We report on the physical location of these stars with reference to possible contamination from ambient H ii emission. Only 13 of the emission-line stars require additional high-resolution spectroscopic observations in order to assign a spectroscopic classification. They have nonetheless been added to the catalogue. Along with flux calibration of the Hα emission, we provide the first Hα luminosity function for selected sub-samples after correction for any possible nebula or ambient contamination. We find a moderate correlation between the intensity of Hα emission and the V magnitude of the central star based on SuperCOSMOS magnitudes and Optical Gravitational Lensing Experiment (OGLE)-II photometry where possible. Cool stars from classes G-S, with and without strong Hα emission, will be the focus of Part II in this series. [ABSTRACT FROM AUTHOR]

We report on new Australian Telescope Compact Array (ATCA) observations of SNR J0519-6902. The Supernova Remnant (SNR) is small in size (~8 pc) and exhibits a typical SNR spectrum with α = -0.53 ± 0.07, with steeper spectral indices towards the northern limb of the remnant. SNR J0519;6902 contains a low level of radially orientated polarisation at wavelengths of 3 and 6 cm, which is typical of younger SNRs. A fairly strong magnetic field was estimated to ~171 µG. The remnant appears to be the result of a typical Type Ia super¬nova, sharing many properties with another small and young Type Ia LMC SNR, J0509-6731. [ABSTRACT FROM AUTHOR]

ABSTRACT We report on the results of observations in the CO(1-0) transition of a complete sample of Southern, intermediate-redshift ( z= 0.2-0.5) ultraluminous infrared galaxies (ULIRGs) using the Mopra 22-m telescope. The 11 ULIRGs with LFIR > 1012.5 L⊙ south of δ=−12° were observed with integration times that varied between 5 and 24 h. Four marginal detections were obtained for individual targets in the sample. The 'stacked' spectrum of the entire sample yields a high significance, 10σ detection of the CO(1-0) transition at an average redshift of z= 0.38. The tightest correlation of LFIR and LCO for published low-redshift ULIRG samples ( z < 0.2) is obtained after normalization of both these measures to a fixed dust temperature. With this normalization the relationship is linear. The distribution of dust-to-molecular hydrogen gas mass displays a systematic increase in dust-to-gas mass with galaxy luminosity for low-redshift samples, but this ratio declines dramatically for intermediate-redshift ULIRGs down to values comparable to that of the Small Magellanic Cloud. The upper envelope to the distribution of ULIRG molecular mass as function of look-back time demonstrates a dramatic rise by almost an order of magnitude from the current epoch out to 5 Gyr. This increase in maximum ULIRG gas mass with look-back time is even more rapid than that of the star formation rate density. [ABSTRACT FROM AUTHOR]

We analyse Spitzer Multiband Imaging Photometer (MIPS) 24- m observations, and Sloan Digital Sky Survey Data Release 7 optical broad-band photometry and spectra, to investigate the star formation (SF) properties of galaxies residing in the Coma supercluster region. We find that SF in dwarf galaxies is quenched only in the high-density environment at the centre of clusters and groups, but that passively evolving massive galaxies are found in all environments, indicating that massive galaxies can become passive via internal processes. The SF–density relation observed for the massive galaxies is weaker relative to the dwarfs, but both show a trend for the fraction of star-forming galaxies ( ) declining to 0 in the cluster cores. We find that active galactic nucleus activity is also suppressed among massive galaxies residing in the cluster cores. We present evidence for a strong dependence of the mechanism(s) responsible for quenching SF in dwarf galaxies on the cluster potential, resulting in two distinct evolutionary pathways. First, we find a significant increase (at the 3 level) in the mean equivalent width of Hα emission among star-forming dwarf galaxies in the infall regions of the Coma cluster and the core of Abell 1367 with respect to the overall supercluster population, indicative of the infalling dwarf galaxies undergoing a starburst phase. We identify these starburst galaxies as the precursors of the post-starburst k + A galaxies. Extending the survey of k + A galaxies over the whole supercluster region, we find 11.4 per cent of all dwarf ( mag 15) galaxies in the Coma cluster and 4.8 per cent in the Abell 1367 have post-starburst like spectra, while this fraction is just 2.1 per cent when averaged over the entire supercluster region (excluding the clusters). This points to a cluster-specific evolutionary process in which infalling dwarf galaxies undergo a starburst and subsequent rapid quenching due to their passage through the dense intracluster medium. In galaxy groups, the SF in infalling dwarf galaxies is instead slowly quenched due to the reduced efficiency of ram-pressure stripping. We show that in the central Mpc of the Coma cluster, the ( ) near-infrared/mid-infrared (MIR) colour of galaxies is correlated with their optical colour and Hα emission, separating all MIR-detected galaxies into two distinct classes of ‘red’ and ‘blue’. By analysing the spatial and velocity distribution of galaxies detected at 24 m in Coma, we find that the (optically) red 24- m detected galaxies follow the general distribution of ‘all’ the spectroscopic members, but their (optically) blue counterparts (i) are almost completely absent in the central Mpc of Coma and (ii) have a remarkable peak in their velocity distribution, corresponding to the mean radial velocity of the galaxy group NGC 4839, suggesting that a significant fraction of the ‘blue’ MIR galaxies are currently on their first infall towards the cluster. The implications of adopting different SF-rate tracers for quantifying evolutionary trends like the Butcher–Oemler effect are also discussed. [ABSTRACT FROM AUTHOR]

We report the results of a near-infrared survey for long-period variables in a field of view of 20× 30 arcmin2 towards the Galactic Centre (GC). We have detected 1364 variables, of which 348 are identified with those reported in Glass et al. We present a catalogue and photometric measurements for the detected variables and discuss their nature. We also establish a method for the simultaneous estimation of distances and extinctions using the period–luminosity relations for the JHKs bands. Our method is applicable to Miras with periods in the range 100–350 d and mean magnitudes available in two or more filter bands. While J band means are often unavailable for our objects because of the large extinction, we estimated distances and extinctions for 143 Miras whose H- and -band mean magnitudes are obtained. We find that most are located at the same distance to within our accuracy. Assuming that the barycentre of these Miras corresponds to the GC, we estimate its distance modulus to be , corresponding to . We have assumed the distance modulus to the Large Magellanic Cloud to be 18.45 mag, and the uncertainty in this quantity is included in the above systematic error. We also discuss the large and highly variable extinction. Its value ranges from 1.5 mag to larger than 4 mag in except towards the thicker dark nebulae and it varies in a complicated way with the line of sight. We have identified mid-infrared counterparts in the Spitzer/IRAC catalogue of Ramírez et al. for most of our variables and find that they follow rather narrow period–luminosity relations in the 3.6–8.0 μm wavelength range. [ABSTRACT FROM AUTHOR]