Quantified H i morphology - I. Multi-wavelength analysis of the THINGS galaxies

Holwerda, Benne W.; Pirzkal, Nor; Blok, W. J. G. de; Bouchard, Antoine; Blyth, S. L.; Heyden, K. J. van der; Elson, Ed

doi:10.1111/j.1365-2966.2011.18938.x

Cited by 38 publications

(95 citation statements)

References 68 publications

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“…Future observations of the molecular gas in these galaxies could provide some insight. A more detailed morphological analysis of the HI akin to that in Holwerda et al (2011) could also provide some clues, but the distances to these galaxies coupled with the short integration times of the observations described here make that type of work less robust.…”

Section: Discussionmentioning

confidence: 99%

Resolved H I Imaging of a Population of Massive H I-Rich Galaxies With Suppressed Star Formation

Lemonias

Schiminovich

Catinella

et al. 2014

ApJ

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Despite the existence of well-defined relationships between cold gas and star formation, there is evidence that some galaxies contain large amounts of HI that do not form stars efficiently. By systematically assessing the link between HI and star formation within a sample of galaxies with extremely high HI masses (log M HI /M ⊙ > 10), we uncover a population of galaxies with an unexpected combination of high HI masses and low specific star formation rates that exists primarily at stellar masses greater than log M * /M ⊙ ∼ 10.5. We obtained HI maps of 20 galaxies in this population to understand the distribution of the HI and the physical conditions in the galaxies that could be suppressing star formation in the presence of large quantities of HI. We find that all of the galaxies we observed have low HI surface densities in the range in which inefficient star formation is common. The low HI surface densities are likely the main cause of the low sSFRs, but there is also some evidence that AGN or bulges contribute to the suppression of star formation. The sample's agreement with the global star formation law highlights its usefulness as a tool for understanding galaxies that do not always follow expected relationships. Subject headings: galaxies: formation -galaxies: evolution 1. INTRODUCTION Many theories of galaxy evolution assume that a galaxy's evolutionary stage and its cold gas content are tightly linked. For example, it is often assumed that a depleted cold gas reservoir can explain why massive galaxies are redder and exhibit less active star formation, but recent observations have challenged this picture by identifying populations of galaxies that contain significant amounts of cold gas despite their low or moderate star formation rates (Morganti et al. 2006;Serra et al. 2012;Young et al. 2013). Some attempts have been made to systematically search for these galaxies to understand them as a population. In this paper we pursue this line of reasoning by studying a sample of massive galaxies with an unusual combination of high HI masses and low specific star formation rates.Galaxies that have more cold gas than expected can be placed into two broad categories: red, early-type galaxies with unexpected measurable HI and galaxies that have significantly more HI than their star formation rates (SFRs) would suggest. In the first category, early-type galaxies were expected to be devoid of cold gas because they lack the spiral arms that indicate recent star formation. The first systematic imaging search for HI in early-type galaxies, motivated in part by the evidence for HI in individual early-types, found that HI is common at low levels in early-type galaxies in the field and could play an important role in their evolution (Morganti et al.

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Section: Discussionmentioning

confidence: 99%

Resolved H I Imaging of a Population of Massive H I-Rich Galaxies With Suppressed Star Formation

Lemonias

Schiminovich

Catinella

et al. 2014

ApJ

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“…We chose to ignore the positive background contribution to asymmetry as the Spitzer data have a very high signal-to-noise ratio and the added asymmetry from sky noise is negligible (see also Holwerda et al 2011d). Fully symmetric galaxies (e.g., ellipticals) would have very low values of asymmetry.…”

Section: Morphological Parametersmentioning

confidence: 99%

“…Uncertainties are based on randomly changing the central position (with the exception of Gini) and a random reshuffle of the pixel values to simulate shot noise. We note that these uncertainties should be viewed as formal errors and do not include the effects of, for example, disk inclination, which has a pronounced effect (see also Bendo et al 2007;Holwerda et al 2011d). We explore the possibility of an ordered morphological list based on these parameters and their ability to select out-ofthe-ordinary or merging morphology in the NIR.…”

Section: Morphology Catalogsmentioning

confidence: 99%

“…Normal spaces have been defined for local samples by Conselice (2003) and Lotz et al (2004) from the visible light image collection originally presented in Frei et al (1996). Morphological parameters from Spitzer IRAC images for the SINGS sample have been reported by Bendo et al (2007), Muñoz-Mateos et al (2009), and Holwerda et al (2011d). We will compare with each of these studies to explore where normal galaxies reside in the morphological parameter space measured at 3.6 and 4.5 μm.…”

Section: Galaxy Classification: Where Normal Galaxies Liementioning

confidence: 99%

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MORPHOLOGICAL PARAMETERS OF ASPITZERSURVEY OF STELLAR STRUCTURE IN GALAXIES

Holwerda

Muñoz-Mateos

Comerón

et al. 2013

ApJ

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The morphology of galaxies can be quantified to some degree using a set of scale-invariant parameters. Concentration (C), asymmetry (A), smoothness (S), the Gini index (G), the relative contribution of the brightest pixels to the secondorder moment of the flux (M 20), ellipticity (E), and the Gini index of the second-order moment (G M) have all been applied to morphologically classify galaxies at various wavelengths. Here, we present a catalog of these parameters for the Spitzer Survey of stellar structure in Galaxies, a volume-limited, near-infrared (NIR) imaging survey of nearby galaxies using the 3.6 and 4.5 μm channels of the Infrared Array Camera on board the Spitzer Space Telescope. Our goal is to provide a reference catalog of NIR quantified morphology for high-redshift studies and galaxy evolution models with enough detail to resolve stellar mass morphology. We explore where normal, noninteracting galaxies-those typically found on the Hubble tuning fork-lie in this parameter space and show that there is a tight relation between concentration (C 82) and M 20 for normal galaxies. M 20 can be used to classify galaxies into earlier and later types (i.e., to separate spirals from irregulars). Several criteria using these parameters exist to select systems with a disturbed morphology, i.e., those that appear to be undergoing a tidal interaction. We examine the applicability of these criteria to Spitzer NIR imaging. We find that four relations, based on the parameters A and S, G and M 20 , G M , C, and M 20 , respectively, select outliers in morphological parameter space, but each selects different subsets of galaxies. Two criteria (G M > 0.6, G > −0.115 × M 20 + 0.384) seem most appropriate to identify possible mergers and the merger fraction in NIR surveys. We find no strong relation between lopsidedness and most of these morphological parameters, except for a weak dependence of lopsidedness on concentration and M 20 .

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“…We then recalculate the parameters for several (x c , y c ) values. After a number of iterations (10) (Holwerda et al 2011c), we compute the rms of the spread in parameter values as an approximate value of the uncertainty in the parameters.…”

Section: Uncertainty Estimationmentioning

confidence: 99%

Morphology parameters: substructure identification in X-ray galaxy clusters

Parekh

Heyden

Ferrari

et al. 2015

A&A

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Context. In recent years multi-wavelength observations have shown the presence of substructures related to merging events in a large proportion of galaxy clusters. Clusters can be roughly grouped into two categories -relaxed and non-relaxed -and a proper characterisation of the dynamical state of these systems is crucial for both astrophysical and cosmological studies. Aims. In this paper we investigate the use of a number of morphological parameters (Gini, M 20 , concentration, asymmetry, smoothness, ellipticity, and Gini of the second-order moment, G M ) introduced to automatically classify clusters as relaxed or dynamically disturbed systems. Methods. We apply our method to a sample of clusters at different redshifts extracted from the Chandra archive and investigate possible correlations between morphological parameters and other X-ray gas properties. Results. We conclude that a combination of the adopted parameters is a very useful tool for properly characterising the X-ray cluster morphology. According to our results, three parameters -Gini, M 20 , and concentration -are very promising for identifying cluster mergers. The Gini coefficient is a particularly powerful tool, especially at high redshift, because it is independent of the choice of the position of the cluster centre. We find that high Gini (>0.65), high concentration (>1.55), and low M 20 (<-2.0) values are associated with relaxed clusters, while low Gini (<0.4), low concentration (<1.0), and high M 20 (>-1.4) characterise dynamically perturbed systems. We also estimate the X-ray cluster morphological parameters in the case of radio loud clusters. Since they are in excellent agreement with previous analyses we confirm that diffuse intracluster radio sources are associated with major mergers.

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Quantified H i morphology - I. Multi-wavelength analysis of the THINGS galaxies

Cited by 38 publications

References 68 publications

Resolved H I Imaging of a Population of Massive H I-Rich Galaxies With Suppressed Star Formation

Resolved H I Imaging of a Population of Massive H I-Rich Galaxies With Suppressed Star Formation

MORPHOLOGICAL PARAMETERS OF ASPITZERSURVEY OF STELLAR STRUCTURE IN GALAXIES

Morphology parameters: substructure identification in X-ray galaxy clusters

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