Non-parametric estimation of morphological lopsidedness

Giese, Nadine; Hulst, J. M. van der; Serra, P.; Oosterloo, Tom

doi:10.1093/mnras/stw1426

Cited by 31 publications

(59 citation statements)

References 36 publications

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“…We create the bias image by placing the SoFiA source mask in a section of the spectral cube not containing any H i signal and integrating the signal in each voxel in the mask to create a moment 0 image. Giese et al (2016) showed that the bias-corrected asymmetry, A map , provides a lower limit on the intrinsic asymmetry and that the asymmetry can be better determined using machine learning and a library of model galaxies, however this is beyond the scope of the current work. We illustrate the calculation for a noiseless model galaxy, the model rotated by 180 • and the absolute residuals which are then summed (left, centre and right panels of Fig.…”

Section: Moment 0 Asymmetrymentioning

confidence: 95%

“…Giese et al (2016) found that the signal to noise ratio (SNR) affects the reliability of the optical parameters when applied to H i maps, with low SNR data not producing meaningful results. Accounting for SNR, Giese et al (2016) found the Conselice et al (2000) asymmetry to be the only parameter to provide useful information for measuring deviations away from a symmetrical disk. Hence from the optical morphology parameters we only consider the Conselice et al (2000) asymmetry.…”

Section: Spatially Resolved Asymmetriesmentioning

confidence: 99%

“…Hence from the optical morphology parameters we only consider the Conselice et al (2000) asymmetry. In this work we only measure morphological and kinematic asymmetries for galaxies resolved by ≥ 3 beams, as Giese et al (2016) found that a galaxy needs to be resolved by three or more beams to distinguish between differing levels of asymmetry.…”

Section: Spatially Resolved Asymmetriesmentioning

confidence: 99%

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H i asymmetries in LVHIS, VIVA, and HALOGAS galaxies

Reynolds

Westmeier

Staveley‐Smith

et al. 2020

Monthly Notices of the Royal Astronomical Society

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We present an analysis of morphological, kinematic and spectral asymmetries in observations of atomic neutral hydrogen (H i) gas from the Local Volume H i Survey (LVHIS), the VLA Imaging of Virgo in Atomic Gas (VIVA) survey and the Hydrogen Accretion in Local Galaxies Survey (HALOGAS). With the aim of investigating the impact of the local environment density and stellar mass on the measured H i asymmetries in future large H i surveys, we provide recommendations for the most meaningful measures of asymmetry for use in future analysis. After controlling for stellar mass, we find signs of statistically significant trends of increasing asymmetries with local density. The most significant trend we measure is for the normalised flipped spectrum residual (A spec ), with mean LVHIS and VIVA values of 0.204 ± 0.011 and 0.615 ± 0.068 at average weighted 10 th nearest-neighbour galaxy number densities of log(ρ 10 /Mpc −3 ) = −1.64 and 0.88, respectively. Looking ahead to the WALLABY survey on the Australian Square Kilometre Array Pathfinder (ASKAP), we estimate that the number of detections will be sufficient to provide coverage over 5 orders of magnitude in both local density and stellar mass increasing the dynamic range and accuracy with which we can probe the effect of these properties on the asymmetry in the distribution of atomic gas in galaxies.

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Section: Moment 0 Asymmetrymentioning

confidence: 95%

Section: Spatially Resolved Asymmetriesmentioning

confidence: 99%

Section: Spatially Resolved Asymmetriesmentioning

confidence: 99%

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H i asymmetries in LVHIS, VIVA, and HALOGAS galaxies

Reynolds

Westmeier

Staveley‐Smith

et al. 2020

Monthly Notices of the Royal Astronomical Society

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“…By characterizing the global H I spectra of around half a million galaxies, we will obtain a wealth of properties, including their systemic and rotational velocities, H I and total dynamical mass estimates, and their profile shape. The latter can be an excellent indicator of environmental effects, with highly symmetric H I profiles typically found in isolated spiral galaxies (Espada et al 2011) and asymmetric H I profiles in galaxies affected by tidal interactions and/or ram pressure stripping (Giese et al 2016;Scott et al 2018). (right).…”

Section: Environment-driven Galaxy Evolutionmentioning

confidence: 99%

WALLABY – an SKA Pathfinder H i survey

Koribalski

Staveley‐Smith

Westmeier

et al. 2020

Astrophys Space Sci

201

125

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The Widefield ASKAP L-band Legacy All-sky Blind surveY (WALLABY) is a next-generation survey of neutral hydrogen (H I) in the Local Universe. It uses the widefield, high-resolution capability of the Australian Square Kilometer Array Pathfinder (ASKAP), a radio interferometer consisting of 36 × 12-m dishes equipped with Phased-Array Feeds (PAFs), located in an extremely radioquiet zone in Western Australia. WALLABY aims to survey three-quarters of the sky (−90 • < δ < +30 • ) to a redshift of z 0.26, and generate spectral line image cubes at ∼30 arcsec resolution and ∼1.6 mJy beam −1 per 4 km s −1 channel sensitivity. ASKAP's instantaneous field of view at 1.4 GHz, delivered by the PAF's 36 beams, is about 30 sq deg. At an integrated signal-to-noise ratio of five, WALLABY is expected to detect around half a million galaxies with a mean redshift of z ∼ 0.05 (∼200 Mpc). The scientific goals of WALLABY include: (a) a census of gas-rich galaxies in the vicinity of the Local Group; (b) a study of the H I properties of galaxies, groups and clusters, in particular the influence of the environment on galaxy evolution; and (c) the refinement of cosmological parameters using the spatial and redshift distribution of low-bias gas-rich galaxies. For context we provide an overview of recent and planned large-scale H I surveys. Combined with existing and new multi-wavelength sky surveys, WALLABY will enable an exciting new generation of panchromatic studies of the Local Universe. -First results from the WALLABY pilot survey are revealed, with initial data products publicly available in the CSIRO ASKAP Science Data Archive (CASDA).

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“…With observed average SFRs of ∼ 3 yr −1 (Bothwell et al 2011) in the local universe it is clear that a typical massive galaxy would use up its gas supply within a few Gigayears if the gas is not replenished or recycled (Kennicutt et al 1994). Besides the SFRs, continuous accretion of gas onto the disc of spiral galaxies can also serve to explain other observed phenomena, such as asymmetries of galactic discs (van Eymeren et al 2011;Giese et al 2016) and warping (García-Ruiz et al 2002) or the chemical composition of the galactic discs (Chiosi 1980). Up to now observations of ongoing accretion have remained elusive in the sense that not enough accretion events are observed to explain the required accretion rates (Sancisi et al 2008).…”

Section: Introductionmentioning

confidence: 99%

Anomalous gas in ESO 149-G003: a MeerKAT-16 view

Józsa

Thorat

Kamphuis

et al. 2020

Monthly Notices of the Royal Astronomical Society

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ESO 149-G003 is a close-by, isolated dwarf irregular galaxy. Previous observations with the ATCA indicated the presence of anomalous neutral hydrogen ($\rm{H{\small I}}$) deviating from the kinematics of a regularly rotating disc. We conducted follow-up observations with the MeerKAT radio telescope during the 16-dish Early Science programme as well as with the MeerLICHT optical telescope. Our more sensitive radio observations confirm the presence of anomalous gas in ESO 149-G003, and further confirm the formerly tentative detection of an extraplanar $\rm{H{\small I}}$ component in the galaxy. Employing a simple tilted-ring model, in which the kinematics is determined with only four parameters but including morphological asymmetries, we reproduce the galaxy’s morphology, which shows a high degree of asymmetry. By comparing our model with the observed $\rm{H{\small I}}$, we find that in our model, we cannot account for a significant (but not dominant) fraction of the gas. From the differences between our model and the observed data cube, we estimate that at least 7–8 per cent of the $\rm{H{\small I}}$ in the galaxy exhibits anomalous kinematics, while we estimate a minimum mass fraction of less than 1 per cent for the morphologically confirmed extraplanar component. We investigate a number of global scaling relations and find that, besides being gas-dominated with a neutral gas-to-stellar mass ratio of 1.7, the galaxy does not show any obvious global peculiarities. Given its isolation, as confirmed by optical observations, we conclude that the galaxy is likely currently acquiring neutral gas. It is either re-accreting gas expelled from the galaxy or accreting pristine intergalactic material.

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Non-parametric estimation of morphological lopsidedness

Cited by 31 publications

References 36 publications

H i asymmetries in LVHIS, VIVA, and HALOGAS galaxies

H i asymmetries in LVHIS, VIVA, and HALOGAS galaxies

WALLABY – an SKA Pathfinder H i survey

Anomalous gas in ESO 149-G003: a MeerKAT-16 view

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