J/ApJ/735/75 HST observations of HII regions in M51 (Lee+, 2011)
H II region luminosity function of the interacting galaxy M51.
Lee J.H., Hwang N., Lee M.G.
<Astrophys. J., 735, 75 (2011)>
=2011ApJ...735...75L 2011ApJ...735...75L
ADC_Keywords: Galaxies, optical ; H II regions
Keywords: galaxies: individual (M51, NGC 5194, NGC 5195) - galaxies: ISM -
galaxies: spiral - H II regions
Abstract:
We present a study of HII regions in M51 using the Hubble Space
Telescope Advanced Camera for Surveys images taken as part of the
Hubble Heritage Program. We have cataloged about 19600 HII regions in
M51 with Hα luminosity in the range of L=1035.5-1039.0erg/s.
The Hα luminosity function of HII regions (HII LF) in M51 is
well represented by a double power law with its index
α=-2.25±0.02 for the bright part and α=-1.42±0.01 for
the faint part, separated at a break point L=1037.1erg/s. This break
was not found in previous studies of M51 HII regions. Comparison with
simulated HII LFs suggests that this break is caused by the transition
of HII region ionizing sources, from low-mass clusters (with
∼103M☉, including several OB stars) to more massive clusters
(including several tens of OB stars). The HII LFs with L<1037.1erg/s
are found to have different slopes for different parts in M51: the HII
LF for the interarm region is steeper than those for the arm and the
nuclear regions. This observed difference in HII LFs can be explained
by evolutionary effects: HII regions in the interarm region are
relatively older than those in the other parts of M51.
Description:
M51 was observed with the HST ACS in 2005 January through the Hubble
Heritage Program (Mutchler et al. 2005AAS...206.1307M 2005AAS...206.1307M). The data set
is composed of images in four filters F435W (B), F555W (V), F814W (I),
and F658N (Hα). The FWHM of a point source is about 0.1".
Throughout this study, we adopt a distance to M51 of 9.9Mpc.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 63 19598 *A catalog of M51 H II regions in the original
sample
table2.dat 59 7215 *A catalog of M51 H II regions in the group sample
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Note on table1.dat and table2.dat: In this study, we present two HII region
catalogs: for the original and group samples. The original sample
includes HII regions detected and provided from HIIPHOT, and the group
sample includes HII regions produced by combining smaller ones in
close proximity into one large one, using the friends-of-friends
algorithm (FOF; Davis et al. 1985ApJ...292..371D 1985ApJ...292..371D). See section 4 for
further explanations.
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See also:
B/hst : HST Archived Exposures Catalog (STScI, 2007)
J/AJ/141/113 : HII regions of M51 and NGC 4449 (Gutierrez+, 2011)
J/ApJS/178/1 : Distribution of HII regions in disk galaxies (Sanchez+, 2008)
J/MNRAS/361/1063 : Oxygen abundances of HII regions (Perez-Montero+, 2005)
J/A+A/397/473 : HST photometry of M51 cluster (Bik+, 2003)
J/A+AS/131/319 : HII regions catalogue (Petit+ 1998)
J/A+A/309/446 : HII Regions in M51 (Petit+, 1996)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 5 I5 --- Seq [1/19598] Index number
7- 17 F11.7 deg RAdeg Right Ascension in decimal degrees (J2000) (1)
19- 27 F9.6 deg DEdeg Declination in decimal degrees (J2000) (1)
29- 36 F8.3 10-19W/m2 FHa [0.43/1841] Hα flux (10-16erg/cm2/s)
38- 43 F6.3 [10-7W] logLHa Log of Hα luminosity [erg/s] (2)
45- 48 F4.2 arcsec ADia [0.18/2.84] Angular diameter (3)
50- 55 F6.2 pc PDia Physical diameter (3)
57 A1 --- Pos [ACIN] Position in the galaxy code (G1)
59- 63 I5 --- GID [10/19591]?=99999 Group sample identification
number
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Note (1): Measured in the F658N (Hα) image.
Note (2): Calculated using L=4πd2*F(Hα) for d=9.9Mpc.
Note (3): Calculated using D=2*(area/π)1/2 where the area is derived
from the number of pixels contained in an H II region.
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Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
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1- 5 I5 --- ID [1/19598] Index number ("GID" if more than one
HII region in table 1, else "Seq" of table 1)
7- 17 F11.7 deg RAdeg Right Ascension in decimal degrees (J2000) (1)
19- 27 F9.6 deg DEdeg Declination in decimal degrees (J2000) (1)
29- 37 F9.3 10-19W/m2 FHa [0.4/17412] Hα flux (10-16erg/cm2/s) (2)
39- 44 F6.3 [10-7W] logLHa Log of Hα luminosity [erg/s] (3)
46- 50 F5.2 arcsec ADia [0.18/12.01] Angular diameter (4)
52- 57 F6.2 pc PDia Physical diameter (4)
59 A1 --- Pos Position in the galaxy code (G1)
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Note (1): Measured in the F658N (Hα) image. Mean positions of all
individual H II regions in a group.
Note (2): Derived from summing the Hα fluxes of all individual
H II regions in a group.
Note (3): Calculated using L=4πd2*F(Hα) for d=9.9Mpc.
Note (4): Calculated using D=2*(area/π)1/2 where the area is derived
from summing the numbers of pixels contained in all individual H II
regions in a group.
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Global Notes:
Note (G1): Position code as follows:
A = Arm region;
I = Interarm region;
N = Nuclear region;
C = NGC 5195.
History:
From electronic version of the journal
(End) Greg Schwarz [AAS], Emmanuelle Perret [CDS] 30-Nov-2012