A5042374450- Galaxies: Formation, Evolution, Phenomena
- Astronomy and Astrophysical Research
- Stellar, planetary, and galactic studies
- Astrophysics and Star Formation Studies
- Gamma-ray bursts and supernovae
- Astrophysical Phenomena and Observations
- Astronomical Observations and Instrumentation
- Spectroscopy and Laser Applications
- Advanced Vision and Imaging
- Astrophysics and Cosmic Phenomena
- Astro and Planetary Science
- Plant Water Relations and Carbon Dynamics
- Adaptive optics and wavefront sensing
- Remote Sensing in Agriculture
- Scientific Research and Discoveries
- Radio Astronomy Observations and Technology
- Atmospheric Ozone and Climate
- Cosmology and Gravitation Theories
- Phase Equilibria and Thermodynamics
- Advanced Image Processing Techniques
- Geophysics and Gravity Measurements
- History and Developments in Astronomy
- Impact of Light on Environment and Health
- Calibration and Measurement Techniques
- Planetary Science and Exploration
University of Victoria
2016-2025
University of Florida
2009
European Southern Observatory
2001-2006
Pontificia Universidad Católica de Chile
2003-2004
European Southern Observatory
2002
University of Cambridge
1999-2001
University of Hawaii at Hilo
1998
University of Kent
1995-1998
Australian Astronomical Observatory
1995-1997
We investigate the effect of metallicity calibrations, AGN classification, and aperture covering fraction on local mass-metallicity (M-Z) relation using 27,730 star-forming galaxies from SDSS Data Release 4. analyze M-Z with 10 including theoretical empirical methods. show that choice calibration has a significant shape y-intercept [12 + log (O/H) ] relation. The absolute scale (y-intercept) varies up to Δ [ = 0.7 dex, depending used, change in is substantial. These results indicate it...
We present new measurements of the free-streaming warm dark matter (WDM) from Lyman-$\alpha$ flux-power spectra. use data medium resolution, intermediate redshift XQ-100 sample observed with X-shooter spectrograph ($z=3 - 4.2$) and high-resolution, high-redshift used in Viel et al. (2013) obtained HIRES/MIKE spectrographs ($z=4.2 5.4$). Based on further improved modelling dependence spectrum matter, cosmological parameters, as well thermal history intergalactic (IGM) hydrodynamical...
(Abridged). We present a sample of 1716 galaxies with companions within Delta v < 500 km/s, r_p 80 kpc and stellar mass ratio 0.1 M_1/M_2 10 from the Sloan Digital Sky Survey (SDSS) Data Release 4 (DR4). In agreement previous studies, we find an enhancement in star formation rate (SFR) galaxy pairs at projected separations 30--40 kpc. addition, that this is highest (and extends to greatest separations) for approximately equal mass, so-called `major' pairs. However, SFR can still be...
We perform two-dimensional, Point-Spread-Function-convolved, bulge+disk decompositions in the $g$ and $r$ bandpasses on a sample of 1,123,718 galaxies from Legacy area Sloan Digital Sky Survey Data Release Seven. Four different decomposition procedures are investigated which make improvements to sky background determinations object deblending over standard SDSS that lead more robust structural parameters integrated galaxy magnitudes colors, especially crowded environments. use set...
Galaxy-galaxy interactions are predicted to cause gas inflows leading enhanced nuclear star formation. In this paper we test the further prediction that lead accretion onto central supermassive black hole, triggering activity in nucleus. Based on a sample of 11,060 SDSS galaxies with close companion (rp < 80 kpc, Delta V 200 km/s), classify AGN based either emission line ratios or spectral classification as quasar. The fraction pairs is compared control 110,600 mass- and redshift-matched no...
In order to investigate the effects of galaxy mergers throughout interaction sequence, we present a study 10,800 galaxies in close pairs and smaller sample 97 post-mergers identified Sloan Digital Sky Survey. We find that average central star formation rate (SFR) enhancement (x 3.5) fraction starbursts (20 per cent) peak post-merger sample. The also show stronger deficit gas phase metallicity than closest pairs, being more metal-poor their control by -0.09 dex. Combined with observed trends...
We present a catalog of bulge, disk, and total stellar mass estimates for ~660,000 galaxies in the Legacy area Sloan Digital Sky Survey Data Release 7. These masses are based on homogeneous g- r-band photometry described by Simard et al. (2011), which we extend here with bulge+disk Sersic profile photometric decompositions SDSS u, i, z bands. discuss methodology used to derive from these data via fitting broadband spectral energy distributions (SEDs), show that typical statistical...
We investigate the origin of galaxy bimodality by quantifying relative role intrinsic and environmental drivers to cessation (or `quenching') star formation in over half a million local Sloan Digital Sky Survey (SDSS) galaxies. Our sample contains wide variety galaxies at z=0.02-0.2, with stellar masses 8 < log(M*/M_sun) 12, spanning entire morphological range from pure disks spheroids, four orders magnitude density halo mass. utilise published rates add this recent GIM2D photometric mass...
Abstract We use pair and environmental classifications of ∼211 000 star-forming galaxies from the Sloan Digital Sky Survey, along with a suite merger simulations, to investigate enhancement star formation as function separation in galaxy pairs. Using new technique for distinguishing between influence nearby neighbours larger scale environment, we find clear out projected separations ∼150 kpc, beyond which there is no net enhancement. strongest enhancements at smallest (especially &lt;20...
Interactions between galaxies are predicted to cause gas inflows that can potentially trigger nuclear activity. Since the inflowing material obscure central regions of interacting galaxies, a potential limitation previous optical studies is obscured Active Galactic Nuclei (AGNs) be missed at various stages along merger sequence. We present first large mid-infrared study AGNs in mergers and galaxy pairs, order quantify incidence triggered by interactions. The sample consists pairs...
In galaxies with significant ongoing star formation there is an impressively tight correlation between total infrared luminosity (L <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:msub><mml:mi/><mml:mrow><mml:mi>T</mml:mi><mml:mi>I</mml:mi><mml:mi>R</mml:mi></mml:mrow></mml:msub></mml:math>) and H display="inline"><mml:mi>α</mml:mi></mml:math> display="inline"><mml:msub><mml:mi/><mml:mrow><mml:mi>H</mml:mi><mml:mi>α</mml:mi></mml:mrow></mml:msub></mml:math>),...
We explore the redshift evolution of metal content damped Lyα systems (DLAs) with new observations four absorbers at z<1.5; together other recently published data, there is now a sample 10 intermediate redshifts for which abundance Zn has been measured. The main conclusion that column density-weighted mean metallicity, [⟨Zn/H⟩]=-1.03±0.23 (on logarithmic scale), not significantly higher z<1.5 than earlier epochs, despite fact comoving star formation rate density universe was near its maximum...
We use a sample of 43,690 galaxies selected from the Sloan Digital Sky Survey Data Release 4 to study systematic effects specific star formation rate (SSFR) and galaxy size (as measured by half-light radius, rh) on mass-metallicity relation. find that with high SSFR or large rh for their stellar mass have systematically lower gas-phase metallicities (by up 0.2 dex) than low small rh. discuss possible origins these dependencies, including galactic winds/outflows, abundance gradients,...
We present the first results from Complete Optical and Radio Absorption Line System (CORALS) survey. have compiled a homogeneous sample of radio-selected QSOs Parkes Catalogue searched for damped Lyman alpha systems (DLAs) towards every target, irrespective its optical magnitude. This approach circumvents selection effects -particularly intervening dust -which long been suspected to affect DLA surveys in optically-selected, magnitude-limited QSO samples. The CORALS data set consists 66 which...
We use a sample of close galaxy pairs selected from the Sloan Digital Sky Survey Data Release 4 (SDSS DR4) to investigate in what environments mergers occur and how results these depend on differences local density. The galaxies are quantified morphologically using two-dimensional bulge-plus-disk decompositions compared control matched stellar mass, redshift projected Lower density have fractionally more with small separations (r_p) relative velocities (Delta v), but even high contain...
We have obtained spectra of 163 quasars at z em > 4.4 with the Gemini Multi Object Spectrometers, largest publicly available sample high-quality, low-resolution these redshifts.From this data set, we generated stacked quasar in three redshift intervals ∼ 5 to model average rest-frame Lyman continuum flux and assess mean free path λ 912 mfp intergalactic medium H I-ionizing radiation.At redshifts q = (4.56,4.86, 5.16), measure (22.2± 2.3, 15.1 ± 1.8, 10.3 1.6) h -1 70 proper Mpc uncertainties...
We present high-resolution spectroscopic observations of GRB 060418, obtained with VLT/UVES. These were triggered using the VLT Rapid-Response Mode (RRM), which allows for automated transient phenomena, without any human intervention. This resulted in first UVES exposure 060418 to be started only 10 min after initial Swift satellite trigger. A sequence spectra covering 330-670 nm acquired at 11, 16, 25, 41 and 71 minutes (mid-exposure) trigger, a resolving power 7 km s-1, signal-to-noise...
We present high spectral resolution Very Large Telescope observations of the broad absorption line quasar SDSS J0318 − 0600. This high-quality data set allows us to extract accurate ionic column densities and determine an electron number density ne = 103.3±0.2 cm−3 for main outflow component. The heavily reddened spectrum J0318-0600 requires purely silicate dust with a reddening curve characteristic predominately large grains, from which we estimate bolometric luminosity. carry out...
We present the largest homogeneous survey of $z>4.4$ damped Lyman-$\alpha$ systems (DLAs) using spectra 163 QSOs that comprise Giant Gemini GMOS (GGG) survey. With this we make most precise high-redshift measurement cosmological mass density neutral hydrogen, $\Omega_{\rm HI}$. At such high redshift important systematic uncertainties in identification DLAs are produced by strong intergalactic medium absorption and QSO continuum placement. These can cause spurious DLA detections, result real...
We have assembled a large, high-quality catalogue of galaxy colours from the Sloan Digital Sky Survey Data Release 7 and identified 21 347 galaxies in pairs spanning range projected separations (rp < 80 h−170 kpc), relative velocities (Δv 10 000 km s−1, which includes that are essential for quality control) stellar mass ratios (from 1:10 to 10:1). find red fraction is higher than control sample matched redshift, demonstrate this difference likely due fact reside density environments...
We present a sample of 1899 galaxies with close companion taken from the SDSS DR7. The galaxy pairs are selected to have velocity differences < 300 km/s, projected separations (rp) 80 kpc/h, mass ratios between 0.1 and 10, robust measurements star formation rates gas-phase metallicities. match in total stellar mass, redshift, local density set 10 control per pair galaxy. For each we can therefore calculate statistical change rate (SFR) metallicity associated interaction process. Relative...
The tight correlation between total galaxy stellar mass and star formation rate (SFR) has become known as the forming main sequence. Using ~487,000 spaxels from galaxies observed part of Sloan Digital Sky Survey Mapping Galaxies at Apache Point Observatory (MaNGA) survey, we confirm previous results that a also exists surface densities (Sigma_SFR) (Sigma_mass) on kpc scales, representing `resolved' new metric (Delta Sigma_SFR), which measures relative enhancement or deficit spaxel-by-spaxel...
The role of galaxy mergers in fueling active galactic nuclei (AGN) is still debated, owing partly to selection effects inherent studies the merger/AGN connection. In particular, luminous AGN are often heavily obscured late-stage mergers. Mid-infrared (IR) color dust-enshrouded with, e.g., Wide-field Infrared Survey Explorer (WISE) has uncovered large new populations AGN. However, this method sensitive mainly that dominate emission from host. To understand how these biases affect mid-IR...
The question of whether galaxy mergers are linked to the triggering active galactic nuclei (AGN) continues be a topic considerable debate. issue can broken down into two distinct questions: 1) Can trigger AGN? 2) Are dominant AGN mechanism? A complete picture AGN-merger connection requires that both these questions addressed with same dataset. In previous work, we have shown selected from Sloan Digital Sky Survey (SDSS) show an excess optically-selected, and mid-IR colour-selected AGN,...