Interactions and star formation activity in Wolf-Rayet galaxies

We present the main results of the PhD Thesis carried out by L\'opez-S\'anchez (2006), in which a detailed morphological, photometrical and spectroscopical analysis of a sample of 20 Wolf-Rayet (WR) galaxies was realized. The main aims are the study of the star formation and O and WR stellar populations in these galaxies and the role that interactions between low surface companion objects have in the triggering of the bursts. We analyze the morphology, stellar populations, physical conditions, chemical abundances and kinematics of the ionized gas, as well as the star-formation activity of each system.Comment: 16 pages, 15 figure

The SAMI Galaxy Survey: The third and final data release

We have entered a new era where integral-field spectroscopic surveys of galaxies are sufficiently large to adequately sample large-scale structure over a cosmologically significant volume. This was the primary design goal of the SAMI Galaxy Survey. Here, in Data Release 3, we release data for the full sample of 3068 unique galaxies observed. This includes the SAMI cluster sample of 888 unique galaxies for the first time. For each galaxy, there are two primary spectral cubes covering the blue (370-570 nm) and red (630-740 nm) optical wavelength ranges at spectral resolving power of R = 1808 and 4304, respectively. For each primary cube, we also provide three spatially binned spectral cubes and a set of standardized aperture spectra. For each galaxy, we include complete 2D maps from parametrized fitting to the emission-line and absorption-line spectral data. These maps provide information on the gas ionization and kinematics, stellar kinematics and populations, and more. All data are available online through Australian Astronomical Optics Data Central

The SAMI galaxy survey: the third and final data release

Galaxie

Galaxy And Mass Assembly (GAMA): data release 4 and the z < 0.1 total and z < 0.08 morphological galaxy stellar mass functions

Galaxie

Ionized and neutral gas in the starburst galaxy NGC 5253

We present our main results of our analysis of the ionized and the neutral gas in the blue compact dwarf galaxy NGC 5253. The ionized gas of its nucleus was studied using VLT UVES data, lending the detection of the weak O and C recombination lines and the confirmation of a localized N (possibly also He) enrichment consequence of chemical pollution by Wolf-Rayet stars. The neutral gas was analyzed using new ATCA data from the LVHIS project and shows a very intriguing kinematics that could suggest that NGC 5253 has interacted with a dwarf gas-rich companion or the nearby M 83. 1 The starburst galaxy NGC 5253 The dwarf galaxy NGC 5253 lies at 4.0 Mpc [4] (at that distance, 1 ” ∼ 19 pc) and has an optical size of ∼ 5 ′ × 2 ′ , giving the appearance of a dwarf elliptical galaxy. Its starbursting nature is revealed using Hα filters [1, 12]: the galaxy shows a lot of ionized gas, including a filamentary structure that is extending perpendicular to its optical major axis. It is therefore classified as a blue compact dwarf (BCD) galaxy, being one of the closest starbursts t

Galaxy And Mass Assembly (GAMA): AUTOZ spectral redshift measurements, confidence and errors

The Galaxy And Mass Assembly (GAMA) survey has obtained spectra of over 230 000 targets using the Anglo-Australian Telescope. To homogenize the redshift measurements and improve the reliability, a fully automatic redshift code was developed (AUTOZ). The measurements were made using a cross-correlation method for both the absorption- and the emission-line spectra. Large deviations in the high-pass-filtered spectra are partially clipped in order to be robust against uncorrected artefacts and to reduce the weight given to single-line matches. A single figure of merit (FOM) was developed that puts all template matches on to a similar confidence scale. The redshift confidence as a function of the FOM was fitted with a tanh function using a maximum likelihood method applied to repeat observations of targets. The method could be adapted to provide robust automatic redshifts for other large galaxy redshift surveys. For the GAMA survey, there was a substantial improvement in the reliability of assigned redshifts and in the lowering of redshift uncertainties with a median velocity uncertainty of 33 km s−1

Galaxy And Mass Assembly: resolving the role of environment in galaxy evolution

We present observations of 18 galaxies from the Galaxy And Mass Assembly (GAMA) survey made with the SPIRAL optical integral field unit (IFU) on the Anglo-Australian Telescope. The galaxies are selected to have a narrow range in stellar mass (6 × 109 0.77 Mpc−2), and 5/11 (45+15−13 per cent) galaxies in low-density environments (<0.77 Mpc−2). We find a weak but not significant relationship of the total SFRs of star-forming galaxies with environment. Due to the size of our sample and the scatter observed we do not draw a definitive conclusion about a possible SFR dependence on environment. Examining the spatial distribution of the Hα emission, we find no evidence for a change in shape or amplitude of the radial profile of star-forming galaxies with environment. If these observations are borne out in larger samples, this would infer that any environment-driven star formation suppression must either act very rapidly (the ‘infall-and-quench’ model) or that galaxies must evolve in a density-dependent manner (an ‘in situ evolution’ model)

The SAMI galaxy survey: Bayesian inference for gas disc kinematics using a hierarchical Gaussian mixture model

We present a novel Bayesian method, referred to as BLOBBY3D, to infer gas kinematics that mitigates the effects of beam smearing for observations using integral field spectroscopy. The method is robust for regularly rotating galaxies despite substructure in the gas distribution. Modelling the gas substructure within the disc is achieved by using a hierarchical Gaussian mixture model. To account for beam smearing effects, we construct a modelled cube that is then convolved per wavelength slice by the seeing, before calculating the likelihood function. We show that our method can model complex gas substructure including clumps and spiral arms. We also show that kinematic asymmetries can be observed after beam smearing for regularly rotating galaxies with asymmetries only introduced in the spatial distribution of the gas. We present findings for our method applied to a sample of 20 star-forming galaxies from the SAMI Galaxy Survey. We estimate the global H α gas velocity dispersion for our sample to be in the range σ¯v ∼[7, 30] km s−1. The relative difference between our approach and estimates using the single Gaussian component fits per spaxel is σ¯v/σ¯v = −0.29 ± 0.18 for the H α flux-weighted mean velocity dispersion