arXiv subjects

Lister Staveley-Smith

Publications and source records attributed to Lister Staveley-Smith.

At least 127 records · Page 7Linked to original sources

arXiv2014

2MTF III. HI 21cm observations of 1194 spiral galaxies with the Green Bank Telescope

We present HI 21cm observations of 1194 galaxies out to a redshift of 10,000 km/s selected as inclined spirals (i>60deg) from the 2MASS Redshift Survey. These observations were carried out at the National Radio Astronomy Observatory Robert C. Byrd Green Bank Telescope (GBT). This observing program is part of the 2MASS Tully-Fisher (2MTF) survey. This project will combine HI widths from these GBT observations with those from further dedicated observing at the Parkes Telescope, from the ALFALFA survey at Arecibo, and S/N>10 and spectral resolution, v_res < 10km/s published widths from a variety of telescopes. We will use these HI widths along with 2MASS photometry to estimate Tully-Fisher distances to nearby spirals and investigate the peculiar velocity field of the local Universe. In this paper we report on detections of neutral hydrogen in emission in 727 galaxies, and measure good signal-to-noise and symmetric HI global profiles suitable for use in the Tully-Fisher relation in 484.

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arXiv2014

ATCA Survey of Ammonia in the Galactic Center: The Temperatures of Dense Gas Clumps between SgrA* and SgrB2

We present a large-scale, interferometric survey of ammonia (1,1) and (2,2) toward the Galactic Center observed with the Australia Telescope Compact Array (ATCA). The survey covers Delta l ~1degree (~150pc) at an assumed distance of 8.5 kpc) and Delta b ~0.2degree (~30pc) which spans the region between the supermassive black hole SgrA* and the massive star forming region SgrB2. The resolution is ~20'' (~0.8pc) and emission at scales >~2' (>~3.2pc) is filtered out due to missing interferometric short spacings. Consequently, the data represent the denser, compact clouds and disregards the large scale, diffuse gas. Many of the clumps align with the 100 pc dust ring and mostly anti-correlate with 1.2cm continuum emission. We present a kinetic temperature map of the dense gas. The temperature distribution peaks at ~38K with a width at half maximum between 18K and 61K (measurements sensitive within Tkin~10-80K). Larger clumps are on average warmer than smaller clumps which suggests internal heating sources. Our observations indicate that the circumnuclear disk ~1.5 pc around SgrA* is supplied with gas by the 20km/s molecular cloud. This gas is substantially cooler than gas ~3-15pc away from SgrA*. We find a strong temperature gradient across SgrB2. Ammonia column densities correlate well with SCUBA 850um fluxes, but the relation is shifted from the origin, which may indicate a requirement for a minimum amount of dust to form and shield ammonia. Around the Arches and Quintuplet clusters we find shell morphologies with UV-influenced gas in their centers, followed by ammonia and radio continuum layers.

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arXiv2013

Are peculiar velocity surveys competitive as a cosmological probe?

Peculiar velocity surveys, which measure galaxy peculiar velocities directly from standard candles in addition to redshifts, can provide strong constraints on the linear growth rate of cosmological large-scale structure at low redshift. The improvement originates from the physical relationship between galaxy density and peculiar velocity, which substantially reduces cosmic variance. We present the results of Fisher matrix forecasts of correlated fields of galaxy density and velocity. Peculiar velocity can improve the growth rate constraints by about a factor of two compared to density alone, if we can use all the information for wavenumber k < 0.2 h/Mpc. Future peculiar velocity surveys, TAIPAN, and the all-sky HI surveys, WALLABY and WNSHS, can measure the growth rate, f*sigma8 to 3 per cent at z ~ 0.025. Although the velocity subsample is about an order of magnitude smaller than the redshift sample from the same survey, it improves the constraint by 40 per cent compared to the same survey without velocity measurements. Peculiar velocity surveys can also measure the growth rate as a function of wavenumber with 15-30 per cent uncertainties in bins with widths 0.01 h/Mpc in the range 0.02 h/Mpc < k < 0.1 h/Mpc, which is a large improvement over galaxy density only. Such measurements on very large scales can detect signatures of modified gravity or non-Gaussianity through scale-dependent growth rate or galaxy bias. We use N-body simulations to improve the modelling of auto- and cross-power spectra of galaxy density and peculiar velocity by introducing a new redshift-space distortion term to the velocity, which has been neglected in previous studies. The velocity power spectrum has a damping in redshift space, which is larger than that naively expected from the similar effect in the galaxy power spectrum.

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arXiv2013

The busy function: a new analytic function for describing the integrated 21-cm spectral profile of galaxies

Accurate parametrization of galaxies detected in the 21-cm HI emission is of fundamental importance to the measurement of commonly used indicators of galaxy evolution, including the Tully-Fisher relation and the HI mass function. Here, we propose a new analytic function, named the 'busy function', that can be used to accurately describe the characteristic double-horn HI profile of many galaxies. The busy function is a continuous, differentiable function that consists of only two basic functions, the error function, erf(x), and a polynomial, |x|^n, of degree n >= 2. We present the basic properties of the busy function and illustrate its great flexibility in fitting a wide range of HI profiles from the Gaussian profiles of dwarf galaxies to the broad, asymmetric double-horn profiles of spiral galaxies. Applications of the busy function include the accurate and efficient parametrization of observed HI spectra of galaxies and the construction of spectral templates for simulations and matched filtering algorithms. We demonstrate the busy function's power by automatically fitting it to the HI spectra of 1000 galaxies from the HIPASS Bright Galaxy Catalog, using our own C/C++ implementation, and comparing the resulting parameters with the catalogued ones. We also present two methods for determining the uncertainties of observational parameters derived from the fit.

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arXiv2013

Detection of HI in distant galaxies using spectral stacking

Using the Parkes radio telescope, we study the 21cm neutral hydrogen (HI) properties of a sample of galaxies with redshifts z<0.13 extracted from the optical 2dF Galaxy Redshift Survey (2dFGRS). Galaxies at 0.04<z<0.13 are studied using new Parkes observations of a 42deg^2 field near the South Galactic Pole (SGP). A spectral stacking analysis of the 3,277 2dFGRS objects within this field results in a convincing 12sigma detection. For the low-redshift sample at 0<z<0.04, we use the 15,093 2dFGRS galaxies observed by the HI Parkes All-Sky Survey (HIPASS) and find a 31sigma stacked detection. We measure average HI masses of (6.93 +/- 0.17)*10^9 h^{-2} Msun and (1.48 +/- 0.03)*10^9 h^{-2} Msun for the SGP and HIPASS samples, respectively. Accounting for source confusion and sample bias, we find a cosmic HI mass density of Omega_HI=(3.19_{-0.59} ^{+0.43})*10^{-4} h^{-1} for the SGP sample and (2.82_{-0.59}^{+0.30})*10^{-4} h^{-1} for the HIPASS sample. This suggests no (12 +/- 23%) evolution in the cosmic HI density over the last ~1h^{-1} Gyr. Due to the very large effective volumes, cosmic variance in our determination of Omega_HI is considerably lower than previous estimates. Our stacking analysis reproduces and quantifies the expected trends in the HI mass and mass-to-light ratio of galaxies with redshift, luminosity and colour.

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arXiv2013

A New 1.4GHz Radio Continuum Map of the Sky South of Declination +25 deg

Archival data from the HI Parkes All-Sky Survey (HIPASS) and the HI Zone of Avoidance (HIZOA) survey have been carefully reprocessed into a new 1.4GHz continuum map of the sky south of declination +25 deg. The wide sky coverage, high sensitivity of 40mK (limited by confusion), resolution of 14'.4 (compared to 51' for the Haslam et al. 408MHz and 35' for the Reich et al. 1.4GHz surveys), and low level of artefacts makes this map ideal for numerous studies, including: merging into interferometer maps to complete large-scale structures; decomposition of thermal and non-thermal emission components from Galactic and extragalactic sources; and comparison of emission regions with other frequencies. The new map is available for download.

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arXiv2013

Confronting Cold Dark Matter Predictions with Observed Galaxy Rotations

The rich statistics of galaxy rotations as captured by the velocity function (VF) provides invaluable constraints on galactic baryon physics and the nature of dark matter (DM). However, the comparison of observed galaxy rotations against cosmological models is prone to subtle caveats that can easily lead to misinterpretations. Our analysis reveals full statistical consistency between ~5000 galaxy rotations, observed in line-of-sight projection, and predictions based on the standard cosmological model (LCDM) at the mass-resolution of the Millennium simulation (HI line-based circular velocities above ~50 km/s). Explicitly, the HI linewidths in the HI Parkes All Sky Survey (HIPASS) are found consistent with those in S3-SAX, a post-processed semi-analytic model for the Millennium simulation. Previously found anomalies in the VF can be plausibly attributed to (1) the mass-limit of the Millennium simulation, (2) confused sources in HIPASS, (3) inaccurate inclination measurements for optically faint sources, and (4) the non-detectability of gas-poor early-type galaxies. These issues can be bypassed by comparing observations and models using linewidth source counts rather than VFs. We investigate if and how well such source counts can constrain the temperature of DM.

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arXiv2013

WISE TF: A Mid-infrared, 3.4-micron Extension of the Tully-Fisher Relation Using WISE Photometry

We present a mid-infrared Tully-Fisher (TF) relation using photometry from the 3.4-micron W1 band of the Wide-field Infrared Survey Explorer (WISE) satellite. The WISE TF relation is formed from 568 galaxies taken from the all-sky 2MASS Tully-Fisher (2MTF) galaxy catalog, spanning a range of environments including field, group, and cluster galaxies. This constitutes the largest mid-infrared TF relation constructed, to date. After applying a number of corrections to galaxy magnitudes and line widths, we measure a master TF relation given by M_corr = -22.24 - 10.05[log(W_corr) - 2.5], with an average dispersion of sigma_WISE = 0.686 magnitudes. There is some tension between WISE TF and a preliminary 3.6-micron relation, which has a shallower slope and almost no intrinsic dispersion. However, our results agree well with a more recent relation constructed from a large sample of cluster galaxies. We additionally compare WISE TF to the near-infrared 2MTF template relations, finding a good agreement between the TF parameters and total dispersions of WISE TF and the 2MTF K-band template. This fact, coupled with typical galaxy colors of (K - W1) ~ 0, suggests that these two bands are tracing similar stellar populations, including the older, centrally-located stars in the galactic bulge which can (for galaxies with a prominent bulge) dominate the light profile.

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arXiv2013

Choirs, HI Galaxy Groups: Catalogue and Detection of Star-forming Dwarf Group Members

Hα observations centred on galaxies selected from the HI Parkes All Sky Survey (HIPASS, Barnes et al. 2001) typically show one and sometimes two star-forming galaxies within the approximately 15-arcminute beam of the Parkes 64-m HI detections. In our Survey of Ionization in Neutral Gas Galaxies (SINGG, Meurer et al. 2006) we found fifteen cases of HIPASS sources containing four or more emission line galaxies (ELGs). We name these fields Choir groups. In the most extreme case we found a field with at least nine ELGs. In this paper we present a catalogue of Choir group members in the context of the wider SINGG sample. The dwarf galaxies in the Choir groups would not be individually detectable in HIPASS at the observed distances if they were isolated, but are detected in SINGG narrow-band imaging due to their membership of groups with sufficiently large total HI mass. The ELGs in these groups are similar to the wider SINGG sample in terms of size, Hα equivalent width, and surface brightness. Eight of these groups have two large spiral galaxies with several dwarf galaxies and may be thought of as morphological analogues of the Local Group. However, on average our groups are not significantly HI-deficient, suggesting that they are at an early stage of assembly, and more like the M81 group. The Choir groups are very compact at typically only 190 kpc in projected distance between the two brightest members. They are very similar to SINGG fields in terms of star formation efficiency (the ratio of star formation rate to HI mass; SFE), showing an increasing trend in SFE with stellar mass.

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arXiv2013

2MTF II. New Parkes 21-cm observations of 303 southern galaxies

We present new 21-cm neutral hydrogen (HI) observations of spiral galaxies for the 2MASS Tully Fisher (2MTF) survey. Using the 64-m Parkes radio telescope multibeam system we obtain 152 high signal-to-noise HI spectra from which we extract 148 high-accuracy (< 5% error) velocity widths and derive reliable rotation velocities. The observed sample consists of 303 southern (δ< -40°) galaxies selected from the MASS Redshift Survey (2MRS) with K_s <11.25 mag, cz < 10,000 km/s and axis ratio b/a < 0.5. The HI observations reported in this paper will be combined with new HI spectra from the Green Bank and Arecibo telescopes, together producing the most uniform Tully-Fisher survey ever constructed (in terms of sky coverage). In particular, due to its near infrared selection, 2MTF will be significantly more complete at low Galactic latitude (|b|<15°) and will provide a more reliable map of peculiar velocities in the local universe.

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arXiv2013

Science with the Murchison Widefield Array

Significant new opportunities for astrophysics and cosmology have been identified at low radio frequencies. The Murchison Widefield Array is the first telescope in the Southern Hemisphere designed specifically to explore the low-frequency astronomical sky between 80 and 300 MHz with arcminute angular resolution and high survey efficiency. The telescope will enable new advances along four key science themes, including searching for redshifted 21 cm emission from the epoch of reionisation in the early Universe; Galactic and extragalactic all-sky southern hemisphere surveys; time-domain astrophysics; and solar, heliospheric, and ionospheric science and space weather. The Murchison Widefield Array is located in Western Australia at the site of the planned Square Kilometre Array (SKA) low-band telescope and is the only low-frequency SKA precursor facility. In this paper, we review the performance properties of the Murchison Widefield Array and describe its primary scientific objectives.

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arXiv2012

GASS High Velocity Clouds in the Region of the Magellanic Leading Arm

We present a catalog of high-velocity clouds in the region of the Magellanic Leading Arm. The catalog is based on neutral hydrogen (\HI) observations from the Parkes Galactic All-Sky Survey (GASS). Excellent spectral resolution allows clouds with narrow-line components to be resolved. The total number of detected clouds is 419. We describe the method of cataloging and present the basic parameters of the clouds. We discuss the general distribution of the high-velocity clouds and classify the clouds based on their morphological type. The presence of a significant number of head-tail clouds and their distribution in the region is discussed in the context of Magellanic System simulations. We suggest that ram-pressure stripping is a more important factor than tidal forces for the morphology and formation of the Magellanic Leading Arm and that different environmental conditions might explain the morphological difference between the Magellanic Leading Arm and Magellanic Stream. We also discuss a newly identified population of clouds that forms the LA IV and a new diffuse bridge-like feature connecting the LA II and III complexes.

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arXiv2012

The 6dF Galaxy Survey: Dependence of halo occupation on stellar mass

In this paper we study the stellar-mass dependence of galaxy clustering in the 6dF Galaxy Survey. The near-infrared selection of 6dFGS allows more reliable stellar mass estimates compared to optical bands used in other galaxy surveys. Using the Halo Occupation Distribution (HOD) model, we investigate the trend of dark matter halo mass and satellite fraction with stellar mass by measuring the projected correlation function, $w_p(r_p)$. We find that the typical halo mass ($M_1$) as well as the satellite power law index ($α$) increase with stellar mass. This indicates, (1) that galaxies with higher stellar mass sit in more massive dark matter halos and (2) that these more massive dark matter halos accumulate satellites faster with growing mass compared to halos occupied by low stellar mass galaxies. Furthermore we find a relation between $M_1$ and the minimum dark matter halo mass ($M_{\rm min}$) of $M_1 \approx 22\,M_{\rm min}$, in agreement with similar findings for SDSS galaxies. The satellite fraction of 6dFGS galaxies declines with increasing stellar mass from 21% at $M_{\rm stellar} = 2.6\times10^{10}h^{-2}\,M_{\odot}$ to 12% at $M_{\rm stellar} = 5.4\times10^{10}h^{-2}\,M_{\odot}$ indicating that high stellar mass galaxies are more likely to be central galaxies. We compare our results to two different semi-analytic models derived from the Millennium Simulation, finding some disagreement. Our results can be used for placing new constraints on semi-analytic models in the future, particularly the behaviour of luminous red satellites. Finally we compare our results to studies of halo occupation using galaxy-galaxy weak lensing. We find good overall agreement, representing a valuable crosscheck for these two different tools of studying the matter distribution in the Universe.

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arXiv2012

Predictions for ASKAP Neutral Hydrogen Surveys

The Australian Square Kilometer Array Pathfinder (ASKAP) will revolutionise our knowledge of gas-rich galaxies in the Universe. Here we present predictions for two proposed extragalactic ASKAP neutral hydrogen (HI) emission-line surveys, based on semi-analytic models applied to cosmological N-body simulations. The ASKAP HI All-Sky Survey, known as WALLABY, is a shallow 3 Pi survey (z = 0 - 0.26) which will probe the mass and dynamics of over 600,000 galaxies. A much deeper small-area HI survey, called DINGO, aims to trace the evolution of HI from z = 0 - 0.43, a cosmological volume of 40 million Mpc^3, detecting potentially 100,000 galaxies. The high-sensitivity 30 antenna ASKAP core (diameter ~2 km) will provide an angular resolution of 30 arcsec (at z=0). Our simulations show that the majority of galaxies detected in WALLABY (87.5%) will be resolved. About 5000 galaxies will be well resolved, i.e. more than five beams (2.5 arcmin) across the major axis, enabling kinematic studies of their gaseous disks. This number would rise to 160,000 galaxies if all 36 ASKAP antennas could be used; the additional six antennas provide baselines up to 6 km, resulting in an angular resolution of 10 arcsec. For DINGO this increased resolution is highly desirable to minimise source confusion; reducing confusion rates from a maximum of 10% of sources at the survey edge to 3%. We estimate that the sources detected by WALLABY and DINGO will span four orders of magnitude in total halo mass (from 10^{11} to 10^{15} Msol) and nearly seven orders of magnitude in stellar mass (from 10^{5} to 10^{12} Msol), allowing us to investigate the process of galaxy formation across the last four billion years.

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arXiv2012

The WiggleZ Dark Energy Survey: the transition to large-scale cosmic homogeneity

We have made the largest-volume measurement to date of the transition to large-scale homogeneity in the distribution of galaxies. We use the WiggleZ survey, a spectroscopic survey of over 200,000 blue galaxies in a cosmic volume of ~1 (Gpc/h)^3. A new method of defining the 'homogeneity scale' is presented, which is more robust than methods previously used in the literature, and which can be easily compared between different surveys. Due to the large cosmic depth of WiggleZ (up to z=1) we are able to make the first measurement of the transition to homogeneity over a range of cosmic epochs. The mean number of galaxies N(<r) in spheres of comoving radius r is proportional to r^3 within 1%, or equivalently the fractal dimension of the sample is within 1% of D_2=3, at radii larger than 71 \pm 8 Mpc/h at z~0.2, 70 \pm 5 Mpc/h at z~0.4, 81 \pm 5 Mpc/h at z~0.6, and 75 \pm 4 Mpc/h at z~0.8. We demonstrate the robustness of our results against selection function effects, using a LCDM N-body simulation and a suite of inhomogeneous fractal distributions. The results are in excellent agreement with both the LCDM N-body simulation and an analytical LCDM prediction. We can exclude a fractal distribution with fractal dimension below D_2=2.97 on scales from ~80 Mpc/h up to the largest scales probed by our measurement, ~300 Mpc/h, at 99.99% confidence.

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arXiv2012

The 6dF Galaxy Survey: z \approx 0 measurement of the growth rate and sigma_8

We present a detailed analysis of redshift-space distortions in the two-point correlation function of the 6dF Galaxy Survey (6dFGS). The K-band selected sub-sample which we employ in this study contains 81971 galaxies distributed over 17000deg^2 with an effective redshift z = 0.067. By modelling the 2D galaxy correlation function, xi(r_p,pi), we measure the parameter combination f(z)sigma_8(z) = 0.423 +/- 0.055. Alternatively, by assuming standard gravity we can break the degeneracy between sigma_8 and the galaxy bias parameter, b. Combining our data with the Hubble constant prior from Riess et al (2011), we measure sigma_8 = 0.76 +/- 0.11 and Omega_m = 0.250 +/- 0.022, consistent with constraints from other galaxy surveys and the Cosmic Microwave Background data from WMAP7. Combining our measurement of fsigma_8 with WMAP7 allows us to test the relationship between matter and gravity on cosmic scales by constraining the growth index of density fluctuations, gamma. Using only 6dFGS and WMAP7 data we find gamma = 0.547 +/- 0.088, consistent with the prediction of General Relativity. We note that because of the low effective redshift of 6dFGS our measurement of the growth rate is independent of the fiducial cosmological model (Alcock-Paczynski effect). We also show that our conclusions are not sensitive to the model adopted for non-linear redshift-space distortions. Using a Fisher matrix analysis we report predictions for constraints on fsigma_8 for the WALLABY survey and the proposed TAIPAN survey. The WALLABY survey will be able to measure fsigma_8 with a precision of 4-10%, depending on the modelling of non-linear structure formation. This is comparable to the predicted precision for the best redshift bins of the Baryon Oscillation Spectroscopic Survey (BOSS), demonstrating that low-redshift surveys have a significant role to play in future tests of dark energy and modified gravity.

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arXiv2012

Cosmological surveys with the Australian Square Kilometre Array Pathfinder

This is a design study into the capabilities of the Australian Square Kilometre Array Pathfinder in performing a full-sky low redshift neutral hydrogen survey, termed WALLABY, and the potential cosmological constraints one can attain from measurement of the galaxy power spectrum. We find that the full sky survey will likely attain 0.6 million redshifts which, when combined with expected Planck CMB data, will constrain the Dark Energy equation of state to 20%, representing a coming of age for radio observations in creating cosmological constraints.

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arXiv2012

The remnant of Supernova 1987A resolved at 3 mm wavelength

The proximity of core-collapse Supernova 1987A (SN1987A) in the Large Magellanic Cloud (LMC) and its rapid evolution make it a unique case study of the development of a young supernova remnant. We aim at resolving the remnant of SN1987A for the first time in the 3-mm band (at 94 GHz). We observed the source at 3-mm wavelength with a 750-m configuration of the Australia Telescope Compact Array (ATCA). We compare the image with a recent 3-cm image and with archival X-ray images. We present a diffraction-limited image with a resolution of 0.7", revealing the ring structure seen at lower frequencies and at other wavebands. The emission peaks in the eastern part of the ring. The 3-mm image bears resemblance to early X-ray images (from 1999-2000). We place an upper limit of 1 mJy (2 σ) on any discrete source of emission in the centre (inside of the ring). The integrated flux density at 3 mm has doubled over the six years since the previous observations at 3 mm. At 3 mm - i.e. within the operational domain of the Atacama Large Millimeter/submillimeter Array (ALMA) - SN1987A appears to be dominated by synchrotron radiation from the inner rim of the equatorial ring, characterised by moderately-weak shocks. There is no clear sign of emission of a different nature, but the current limits do not rule out such component altogether.

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