J/MNRAS/416/2437 Quantified H I morphology of WHISP sample (Holwerda+, 2011)
Quantified H I morphology. IV. The merger fraction and rate in WHISP.
Holwerda B.W., Pirzkal N., de Blok W.J.G., Bouchard A., Blyth S.-L.,
Van Der Heyden K.J.
<Mon. Not. R. Astron. Soc., 416, 2437-2446 (2011)>
=2011MNRAS.416.2437H 2011MNRAS.416.2437H
ADC_Keywords: Galaxies, nearby ; H I data ; Morphology
Keywords: galaxies: fundamental parameters - galaxies: interactions -
galaxies: kinematics and dynamics - galaxies: spiral -
galaxies: structure
Abstract:
The morphology of the atomic hydrogen (HI) disc of a spiral galaxy is
the first component to be disturbed by a gravitational interaction
such as a merger between two galaxies. We use a simple parametrization
of the morphology of HI column density maps of the Westerbork
observations of neutral Hydrogen in Irregular and SPiral galaxies
(WHISP) project to select those galaxies that are likely undergoing a
significant interaction. Merging galaxies occupy a particular part of
parameter space defined by Asymmetry (A), the relative contribution of
the 20 per cent brightest pixels to the second-order moment of the
column density map (M20) and the distribution of the second-order
moment over all the pixels (GM).
Based on their HI morphology, we find that 13 per cent of the WHISP
galaxies are in an interaction (Concentration-M20) and only 7 per
cent are based on close companions in the data cube. This apparent
discrepancy can be attributed to the difference in visibility
time-scales: mergers are identifiable as close pairs for 0.5 Gyr but
are identifiable for ∼1Gyr by their disturbed HI morphology. Expressed
as volume merger rates, the two estimates agree very well: 7 and
6.8x10-3mergers/Gyr/Mpc3 for paired and morphologically disturbed
HI discs, respectively.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
tablea1.dat 103 339 Morphological parameters for the complete
WHISP sample
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See also:
J/AJ/136/2563 : HI Nearby Galaxy Survey, THINGS (Walter+, 2008)
J/MNRAS/416/2401 : Quantified H I morphology. I (Holwerda+, 2011)
J/MNRAS/416/2415 : Quantified H I morphology. II (Holwerda+, 2011)
J/MNRAS/427/3159 : Quantified H I morphology. VI (Holwerda+, 2012)
Byte-by-byte Description of file: tablea1.dat
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Bytes Format Units Label Explanations
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1- 5 I05 --- UGC UGC number
7- 11 F5.3 --- Gini ? Gini parameter (1)
13- 17 F5.3 --- e_Gini ? rms uncertainty on Gini
19- 24 F6.3 --- M20 ? Moment of light parameter
26- 30 F5.3 --- e_M20 ? rms uncertainty on M20
32- 37 F6.3 --- C ? Concentration parameter, C=5log(r80/r20)
39- 43 F5.3 --- e_C ? rms uncertainty on C
45- 49 F5.3 --- A ? Asymetry parameter
51- 55 F5.3 --- e_A ? rms uncertainty on A
57- 61 F5.3 --- S ? Smoothness parameter
63- 67 F5.3 --- e_S ? rms uncertainty on S
69- 73 F5.3 --- Ell ? Ellipticity
75- 79 F5.3 --- e_Ell ? rms uncertainty on Ell
81- 85 F5.3 --- GM ? Gini of the second-order moment parameter
87- 91 F5.3 --- e_GM ? rms uncertainty on GM
93- 97 F5.3 --- Axy ? Index of x and y axis symmetry
99-103 F5.3 --- e_Axy ? rms uncertainty on Axy
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Note (1): Gini parameter quantifies the distribution of flux over the
pixels in an image. The Gini parameter is an indication of equality
in a distribution, with G=0 the perfect equality (all pixels have the
same intensity) and G=1 perfect inequality (all the intensity is in a
single pixel).
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History:
From electronic version of the journal
References:
Holwerda et al., Paper I 2011MNRAS.416.2401H 2011MNRAS.416.2401H, Cat. J/MNRAS/416/2401
Holwerda et al., Paper II 2011MNRAS.416.2415H 2011MNRAS.416.2415H, Cat. J/MNRAS/416/2415
Holwerda et al., Paper III 2011MNRAS.416.2426H 2011MNRAS.416.2426H
Holwerda et al., Paper V 2011MNRAS.416.2447H 2011MNRAS.416.2447H
Holwerda et al., Paper VI 2012MNRAS.427.3159H 2012MNRAS.427.3159H, Cat. J/MNRAS/427/3159
(End) Patricia Vannier [CDS] 13-Apr-2012