Systematically asymmetric: a comparison of H i profile asymmetries in real and simulated galaxies

ABSTRACT We examine different measures of asymmetry for galaxy H i velocity profiles. We introduce the channel-by-channel asymmetry and the velocity-of-equality statistics to quantify profile asymmetries. Using a sample of simulated galaxies, we examine how these and the standard lopsidedness morphometric statistic depend on a variety of observational effects, including the viewing angle and inclination. We find that our newly introduced channel-by-channel asymmetry is less sensitive to the effects of viewing angle and inclination than other morphometrics. Applying our statistics to the WHISP (Westerbork H i survey of Irregular and SPiral galaxies) H i galaxy sample, we also find that the channel-by-channel asymmetry is a better indicator of visually classified asymmetric profiles. In addition, we find that the lopsidedness–velocity of equality space can be used to identify profiles with deep central dips without visual inspection.

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Bar effect on gas-phase abundance gradients – II. Luminosity-dependent flattening

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/staa2208 ◽

2020 ◽

Vol 500 (2) ◽

pp. 2380-2400

Author(s):

A Zurita ◽

E Florido ◽

F Bresolin ◽

I Pérez ◽

E Pérez-Montero

Keyword(s):

Gas Phase ◽

Spiral Galaxies ◽

H Ii Regions ◽

Lower Mass ◽

Chemical Abundances ◽

Barred Galaxies ◽

The Galaxy ◽

Galaxy Sample ◽

Nearby Galaxies ◽

Lower Luminosity

ABSTRACT We present here the second part of a project that aims at solving the controversy regarding the issue of the bar effect on the radial distribution of metals in the gas-phase of spiral galaxies. In Paper I, we presented a compilation of more than 2800 H ii regions belonging to 51 nearby galaxies for which we derived chemical abundances and radial abundance profiles from a homogeneous methodology. In this paper, we analyse the derived gas-phase radial abundance profiles of 12+log (O/H) and log (N/O), for barred and unbarred galaxies separately, and find that the differences in slope between barred and unbarred galaxies depend on galaxy luminosity. This is due to a different dependence of the abundance gradients (in dex kpc−1) on luminosity for the two types of galaxies: in the galaxy sample under consideration the gradients appear to be considerably shallower for strongly barred galaxies in the whole luminosity range, while profile slopes for unbarred galaxies become steeper with decreasing luminosity. Therefore, we only detect differences in slope for the lower luminosity (lower mass) galaxies (MB ≳ −19.5 or M* ≲ 1010.4 M⊙). We discuss the results in terms of the disc evolution and radial mixing induced by bars and spiral arms. Our results reconcile previous discrepant findings that were biased by the luminosity (mass) distribution of the sample galaxies and possibly by the abundance diagnostics employed.

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Evidence for dark matter on different scales from the KLUN galaxy sample

International Astronomical Union Colloquium ◽

10.1017/s0252921100055457 ◽

2000 ◽

Vol 174 ◽

pp. 457-461

Author(s):

M. O. Hanski ◽

P. Teerikorpi ◽

T. Ekholm ◽

G. Theureau ◽

Yu. Baryshev ◽

...

Keyword(s):

Dark Matter ◽

Spiral Galaxies ◽

Zero Point ◽

Morphological Type ◽

Selection Effects ◽

Local Universe ◽

Galaxy Distribution ◽

Galaxy Sample ◽

Fisher Relation ◽

Large Clusters

The KLUN (Kinematics of the Local UNiverse) sample of 6600 spiral galaxies is used in studying dark matter on different scales: •The Morphological Type dependence of the zero-point of the Tully-Fisher relation indicates mass to light ratio M/L ≈ 9 − 16 on galactic scales.•Preliminary results from a study of selection effects influencing double galaxies give a larger value M/L ≈ 30 − 50.•Study of the Perseus-Pisces supercluster, using Malmquist bias corrected TF distances and Tolman-Bondi solutions indicates M/L ≈ 200 − 600 for large clusters. Similar results were obtained in our previous work on Virgo galaxies.•Application of a modified version of Sandage-Tammann-Hardy test of the linearity of Hubble law inside the observed hierarchical (fractal) galaxy distribution up to 200 Mpc suggests that either Ω0 is very small (0.01) or the major part of the matter is uniformly distributed dark matter.

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The Rotation of Spiral Galaxies: Infall Model vs. Observations

Symposium - International Astronomical Union ◽

10.1017/s0074180900137118 ◽

1988 ◽

Vol 130 ◽

pp. 584-584

Author(s):

Ricardo A. Flores

Keyword(s):

Dark Matter ◽

Relative Abundance ◽

Spiral Galaxies ◽

Velocity Profiles ◽

Intermediate Region ◽

Independent Variables ◽

Circular Velocity ◽

Two Independent Variables ◽

Adiabatic Contraction

The infall model of the rotation of spiral galaxies predicts that the morphology of their velocity profiles and the relative abundance of dark matter (DM) in the intermediate region between, roughly, 3 and 5 scale lengths of their exponential disks is the result of the adiabatic contraction of the cores of their DM halos due to the dissipative infall of the gas destined to form the visible core of the galaxies. We compare the model with a few observations in a plane defined by two independent variables that can be calculated for the model and the observations. The model predicts substantially more DM interior to the optical radii of the galaxies than is allowed by the “maximum disk” hypothesis (i.e. the inner circular velocity is almost entirely due to the disk matter. However, a different version of the “maximum disk” idea might agree with the model: see the discussion by E. Athanassoula in these Proceedings). An analysis of the observations that is independent of this hypothesis indicates DM in abundance that agrees with the model. The data sample, unfortunately, is too small to draw yet any definitive conclusion on the validity of the model

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How Socially Relevant Visual Characteristics of Avatars Influence Impression Formation

Journal of Media Psychology Theories Methods and Applications ◽

10.1027/1864-1105/a000005 ◽

2010 ◽

Vol 22 (1) ◽

pp. 37-43 ◽

Cited By ~ 13

Author(s):

David Weibel ◽

Daniel Stricker ◽

Bartholomäus Wissmath ◽

Fred W. Mast

Keyword(s):

Impression Formation ◽

Pupil Size ◽

Conscious Perception ◽

Viewing Angle ◽

Frontal View ◽

Computer Mediated ◽

First Impression ◽

Visual Characteristics ◽

Socially Relevant ◽

Blink Frequency

Like in the real world, the first impression a person leaves in a computer-mediated environment depends on his or her online appearance. The present study manipulates an avatar’s pupil size, eyeblink frequency, and the viewing angle to investigate whether nonverbal visual characteristics are responsible for the impression made. We assessed how participants (N = 56) evaluate these avatars in terms of different attributes. The findings show that avatars with large pupils and slow eye blink frequency are perceived as more sociable and more attractive. Compared to avatars seen in full frontal view or from above, avatars seen from below were rated as most sociable, self-confident, and attractive. Moreover, avatars’ pupil size and eyeblink frequency escape the viewer’s conscious perception but still influence how people evaluate them. The findings have wide-ranging applied implications for avatar design.

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