J/AJ/142/183 HST photometry of globulars in M81 (NGC 3031) (Nantais+, 2011)
Hubble space telescope photometry of globular clusters in M81.
Nantais J.B., Huchra J.P., Zezas A., Gazeas K., Strader J.
<Astron. J., 142, 183 (2011)>
=2011AJ....142..183N 2011AJ....142..183N
ADC_Keywords: Photometry, HST ; Clusters, globular ; Galaxies, nearby ;
Cross identifications
Keywords: galaxies: individual (M81) - galaxies: spiral -
galaxies: star clusters: general - galaxies: stellar content
Abstract:
We perform aperture photometry and profile fitting on 419 globular
cluster (GC) candidates with mV≤23mag identified in Hubble Space
Telescope/Advanced Camera for Surveys (HST/ACS) BVI imaging, and
estimate the effective radii of the clusters. We identify 85
previously known spectroscopically confirmed clusters, and newly
identify 136 objects as good cluster candidates within the 3σ
color and size ranges defined by the spectroscopically confirmed
clusters, yielding a total of 221 probable GCs. The luminosity
function peak for the 221 probable GCs with estimated total
dereddening applied is V~(20.26±0.13)mag, corresponding to a
distance of ∼3.7±0.3Mpc. The blue and red GC candidates, and the
metal-rich and metal-poor spectroscopically confirmed clusters,
respectively, are similar in half-light radius. Red confirmed clusters
are about 6% larger in median half-light radius than blue confirmed
clusters, and red and blue good GC candidates are nearly identical in
half-light radius. The total population of confirmed and "good"
candidates shows an increase in half-light radius as a function of
galactocentric distance.
Description:
Our 419 M81 globular cluster candidates were observed with HST/ACS
Wide Field Camera in the F435W (B), F606W (V), and F814W (I)
passbands. The B and V imaging comes from HST program GO-10584 (PI:
Andreas Zezas; 2005 december to 2006 december). The I-band imaging
comes primarily from HST program GO-10250 (PI: John Huchra; 2005
september and 2006 september) with five additional images from
GO-10584.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table2.dat 57 419 Basic object information
table3.dat 57 419 Photometry of globular cluster (GC) candidates
table4.dat 44 419 Sizes and projected galactocentric distances of
globular cluster (GC) candidates
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See also:
B/hst : HST Archived Exposures Catalog (STScI, 2007)
VII/155 : Third Reference Cat. of Bright Galaxies (RC3) (de Vaucouleurs+ 1991)
J/AJ/109/1055 : Globulars of M81 (Perelmuter+ 1995)
J/AJ/122/1330 : HST BVI photometry of M81 star clusters (Chandar+, 2001)
J/MNRAS/405/1293 : Compact star clusters in M81 (Santiago-Cortes+, 2010)
J/AJ/139/2620 : Spectroscopy of M81 globular clusters (Nantais & Huchra, 2010)
J/AJ/139/1413 : M81 star cluster candidates (Nantais+, 2010)
Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
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1- 3 I3 --- ID [1/419] Object ID number
5 I1 h RAh [9] Hour of Right ascension (J2000)
7- 8 I2 min RAm [53/57] Minute of Right ascension (J2000)
10- 15 F6.3 s RAs Second of Right ascension (J2000)
17 A1 --- DE- [+] Sign of Declination (J2000)
18- 19 I2 deg DEd [68/69] Degree of Declination (J2000)
21- 22 I2 arcmin DEm Arcminute of Declination (J2000)
24- 29 F6.3 arcsec DEs Arcsecond of Declination (J2000)
31- 34 I4 --- [NHM2010] [20/2506]? I-band catalog ID number (1)
36- 40 I5 --- [PR95] [40193/60012]? Perelmuter & Racine catalog
ID number (2)
42- 44 I3 --- [CFT2001] [1/112]? Chandar, Ford, & Tsvetanov catalog
ID number (3)
46- 57 A12 --- Spec Spectroscopic confirmation (4)
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Note (1): Nantais et al. 2010, Cat. J/AJ/139/1413, I-band catalog ID number;
<[NHM2010] NNNN> in Simbad.
Note (2): Perelmuter & Racine 1995, Cat. J/AJ/109/1055, catalog ID number;
<[PR95] NNNNN> in Simbad.
Note (3): Chandar, Ford, & Tsvetanov 2001, Cat. J/AJ/122/1330, catalog ID
number; <[CFT2001] NNN> in Simbad.
Note (4): Reference as follows:
(a) = Perelmuter, Brodie, and Huchra (1995AJ....110..620P 1995AJ....110..620P);
(b) = Schroder et al. (2002AJ....123.2473S 2002AJ....123.2473S);
(c) = Nantais and Huchra (2010, J/AJ/139/2620);
(d) = Brodie and Huchra (1991ApJ...379..157B 1991ApJ...379..157B).
If not a globular cluster, object type is specified:
Gx = galaxy;
HII = HII region.
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Byte-by-byte Description of file: table3.dat
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Bytes Format Units Label Explanations
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1- 3 I3 --- ID [1/419] Object ID number
5- 9 F5.2 mag Vmag [16.92/23.5] The HST V band magnitude (F606W)
11- 14 F4.2 mag e_Vmag [0.02/0.09] The 1-σ error in Vmag
16- 19 F4.2 mag B-V [0.13/1.93] B-V color index (F435W-F606W)
21- 24 F4.2 mag e_B-V [0.03/0.41] The 1-σ error in B-V
26- 29 F4.2 mag V-I [0.38/1.96] V-I color index (F606W-F814W)
31- 34 F4.2 mag e_V-I [0.03/0.41] The 1-σ error in V-I
36- 39 F4.2 arcsec Apert [0.5/3] Aperture photometry radius (5)
41- 46 F6.3 pix FWHM.p [2.53/59.06] Full width at half maximum
measured w/RADPROF in IRAF
47 A1 --- --- [0]
49- 51 A3 --- Flag [bvi ] Image edge object flag (6)
53- 57 A5 --- Qph Quality of GC candidate from photometry (G1)
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Note (5): For integrated V magnitude. Based on where the radial profile of the
cluster light blended into the background.
Note (6): Indicates which bands (b=B, v=V, i=I) are affected by the
object being at the edge of a frame or between frames.
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Byte-by-byte Description of file: table4.dat
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Bytes Format Units Label Explanations
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1- 3 I3 --- ID [1/419] Object ID number
5- 9 A5 --- Qmod Quality of GC candidate from model parameters (G1)
11- 15 F5.2 mag Vmag [16.92/23.52] The HST V band magnitude
17- 21 F5.2 kpc pDist [0.34/11.76] Projected galactocentric distance
23- 27 F5.2 pix FWHM.m [0.43/24.65]? FWHM along major axis (7)
29- 32 F4.2 --- b/a [0.27/1]? Axis ratio; minor/major (7)
34- 38 F5.2 pc Rh [0.46/27.29]? Half-light radius (7)
40- 44 F5.2 pc e_Rh [0.38/12.46]? The 1-σ error in Rh (7)(8)
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Note (7): Parameters fit by ISHAPE King model (based on ISHAPE software; Larsen
1999, cat. J/A+AS/139/393).
Note (8): The uncertainty was estimated based on the average absolute values of
the upper and lower error bars in the major and minor axis FWHMs,
converted into parsecs, and added in quadrature to the standard
deviation of half-light radius values determined using linear
concentration parameters of 5, 15, 20, 30, 50, 75, and 100.
Uncertainties estimated in this way were typically around 40%, rather
high but probably reasonable given not knowing the concentration
parameter for each cluster. See section 5.4 for further explanations.
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Global note:
Note (G1): Quality code are:
conf = spectroscopically confirmed GC;
good = within 3-σ color and size ranges defined using
confirmed clusters;
fair = within 3-σ color ranges but not 3-σ size range;
poor = outside of 3-σ color ranges;
nongc = spectroscopically confirmed as a non-GC.
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History:
From electronic version of the journal
(End) Greg Schwarz [AAS], Sylvain Guehenneux [CDS] 19-Mar-2013