J/A+A/586/A102 UCDs in the halo of NGC1399 (Voggel+, 2016)
Globular cluster clustering and tidal features around ultra-compact dwarf
galaxies in the halo of NGC 1399.
Voggel K., Hilker M., Richtler T.
<Astron. Astrophys., 586, A102-102 (2016)>
=2016A&A...586A.102V 2016A&A...586A.102V (SIMBAD/NED BibCode)
ADC_Keywords: Galaxies, nearby ; Associations, stellar ; Clusters, globular
Keywords: galaxies: clusters: individual: NGC 1399 - galaxies: dwarf -
galaxies: fundamental parameters - galaxies: nuclei -
galaxies: star clusters: general
Abstract:
We present a novel approach to constrain the formation channels of
ultra-compact dwarf galaxies (UCDs). They most probably are an
inhomogeneous class of objects, composed of remnants of tidally
stripped dwarf elliptical galaxies and star clusters that occupy the
high mass end of the globular cluster luminosity function. We use
three methods to unravel their nature: 1) we analyzed their surface
brightness profiles; 2) we carried out a direct search for tidal
features around UCDs; and 3) we compared the spatial distribution of
GCs and UCDs in the halo of their host galaxy. Based on FORS2
observations under excellent seeing conditions, we studied the
detailed structural composition of a large sample of 97 UCDs in the
halo of NGC1399, the central galaxy of the Fornax cluster, by
analyzing their surface brightness profiles. We found that 13 of the
UCDs were resolved above the resolution limit of 23pc and we derived
their structural parameters fitting a single Sersic function. When
decomposing their profiles into composite King and Sersic profiles, we
find evidence for faint stellar envelopes at µ≃26mag/arcsec2,
surrounding the UCDs up to an extension of 90pc in radius. We also
show new evidence for faint asymmetric structures and tidal tail-like
features surrounding several of these UCDs, a possible tracer of their
origin and assembly history within their host galaxy halos. In
particular, we present evidence for the first discovery of a
significant tidal tail with an extension of ∼350pc around UCD-FORS2.
Finally, we studied the local overdensities in the spatial
distribution of globular clusters within the halo of NGC1399 out to
110kpc to see if they are related to the positions of the UCDs. We
found a local overabundance of globular clusters on a scale of ≤1kpc
around UCDs, when we compared it to the distribution of globulars from
the host galaxy. This effect is strongest for the metal-poor blue GCs.
We discuss how likely it is that these clustered globulars were
originally associated with the UCD, either as globular cluster systems
of a nucleated dwarf galaxy that was stripped down to its nucleus, or
as a surviving member of a merged super star cluster complex.
Description:
To study UCDs within the Fornax cluster, we used data from ESO program
076.B-0520 (PI:Richtler). The imaging data were taken in the nights
October 9th and 10th, 2005, with the high-resolution collimator mode
of FORS2, which is mounted on UT1 of the Very Large Telescope (VLT).
Three separate fields were observed in the R-band. Fields 1 and 2 with
3x800s exposure time each and field 3 with 5x800s.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 96 13 Results from the Sersic fits for those 13 UCDs
that have half-light radii larger than the
resolution limit of 23 pc
tablea1.dat 89 21 UCD and companion properties of all 19 objects
for which a faint point source was found
within r<300pc (see Fig. 9)
tablea2.dat 63 71 UCDs from the original sample of 97 in the FORS
fields, which are not yet listed in Table 1 or
as a companion hosting UCD in Table A.1
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See also:
J/A+A/383/823 : Radial velocities of UCOs in Fornax (Mieske+, 2002)
J/AJ/127/2114 : Globular clusters around NGC 1399 (Dirsch+, 2004)
J/A+A/418/445 : FCOS Ultra Compact Dwarf galaxies radial vel. (Mieske+ 2004)
J/A+A/513/A52 : Velocities of NGC 1399 globular clusters (Schuberth+, 2010)
J/MNRAS/382/1342 : Compact stellar systems around NGC 1399 (Firth+, 2007)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 8 A8 --- --- [UCD-FORS -]
10- 11 I2 --- UCD-FORS UCD-FORS number
13- 18 A6 --- AName Alternative name (G1)
20 A1 --- n_AName [abc] Note on AName (1)
23 I1 h RAh Right ascension (J2000)
25- 26 I2 min RAm Right ascension (J2000)
28- 32 F5.2 s RAs Right ascension (J2000)
34 A1 --- DE- Declination sign (J2000)
35- 36 I2 deg DEd Declination (J2000)
38- 39 I2 arcmin DEm Declination (J2000)
41- 44 F4.1 arcsec DEs Declination (J2000)
46- 50 F5.2 mag Vmag UCD V magnitude
52- 56 F5.3 mag e_Vmag rms uncertainty on Vmag
58- 62 F5.2 pc Reff Effective temperature
64- 67 F4.2 pc e_Reff rms uncertainty on Reff (2)
69- 72 F4.2 --- n Sersic index
74- 77 F4.2 --- e_n rms uncertainty on n (2)
79- 82 F4.2 mag V-I UCD V-I colour index (3)
84- 87 F4.2 mag e_V-I rms uncertainty on V-I
89- 92 I4 km/s RV Radial velocity (3)
94- 96 I3 km/s e_RV rms uncertainty on RV
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Note (1): Some of these objects were also presented in Richtler et al.
(2008A&A...478L..23R 2008A&A...478L..23R) with the following names:
a = 78:12, [DRG2004] 78:12 in Simbad
b = 91:93, [DRG2004] 91:93 in Simbad
c = 90:12, [DRG2004] 90:12 in Simbad
Note (2): The provided errors on Reff and n are those given by GALFIT, which
should be taken with caution because close to the resolution limit these
errors might be underestimated.
Note (3): The (V-I) colors and radial velocities are taken from the respective
original samples.
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Byte-by-byte Description of file: tablea1.dat
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Bytes Format Units Label Explanations
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1 A1 --- Ref Reference used in Fig. 9
3- 10 A8 --- --- [UCD-FORS -]
12- 13 I2 --- UCD-FORS UCD-FORS number
15- 20 A6 --- AName Alternative name
23 I1 h RAh Right ascension (J2000)
25- 26 I2 min RAm Right ascension (J2000)
28- 32 F5.2 s RAs Right ascension (J2000)
34 A1 --- DE- Declination sign (J2000)
35- 36 I2 deg DEd Declination (J2000)
38- 39 I2 arcmin DEm Declination (J2000)
41- 44 F4.1 arcsec DEs Declination (J2000)
46- 50 F5.2 mag Vmag UCD V magnitude
52- 55 F4.2 mag V-I UCD V-I colour index
57- 61 F5.2 mag Vcomp V magnitude of the possible companion
63- 65 I3 pc Distc Distance of the companion to the UCD
67- 71 F5.2 kpc DisttN Distance of the UCD to the center of NCG 1399
73- 75 I3 pc r Tidal radius (1)
77- 80 F4.2 --- Distc/r Fraction between Distc/r (2)
82- 85 I4 km/s RV Radial Velocity
87- 89 I3 km/s e_RV rms uncertainty on RV
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Note (1): estimate of the tidal radius of this UCD for it's specific position
using the formula given in 8.
Note (2): If this fraction is smaller than 1.0 the companion lies within the
tidal radius of the UCD host object, which is the case for 16 of our 19 UCDs.
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Byte-by-byte Description of file: tablea2.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 8 A8 --- --- [UCD-FORS -]
10- 11 I2 --- UCD-FORS UCD-FORS number
13- 18 A6 --- AName Alternative name (G1)
21 I1 h RAh Right ascension (J2000)
23- 24 I2 min RAm Right ascension (J2000)
26- 30 F5.2 s RAs Right ascension (J2000)
32 A1 --- DE- Declination sign (J2000)
33- 34 I2 deg DEd Declination (J2000)
36- 37 I2 arcmin DEm Declination (J2000)
39- 42 F4.1 arcsec DEs Declination (J2000)
44- 48 F5.2 mag Vmag UCD V magnitude
50- 53 F4.2 mag e_Vmag rms uncertainty on Vmag
55- 58 F4.2 mag V-I UCD V-I colour index
60- 63 F4.2 mag e_V-I rms uncertainty on V-I
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Global notes:
Note (G1): The alternative object names from the literature are from the
following sources:
UCDx = Firth et al. (2007, Cat. J/MNRAS/382/1342) [DJG2000] UCO XX in Simbad
X_xxx = Mieske et al. (2002, Cat. J/A+A/383/823 & 2004, Cat. J/A+A/418/445
FCOS F-NNNN in Simbad
Yxxx = Richtler et al. (2008A&A...478L..23R 2008A&A...478L..23R), [MHB2008] Yxxx in Simbad
or from Schuberth et al. (2010, Cat. J/A+A/513/A52),
[SRH2010] NN NNN, [SRH2010] GS0N-M0N NNN in Simbad
NN.NNN = Dirsch et al. (2014, Cat. J/AJ/127/2114), [DRG2004] NN:NNN in Simbad
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History:
From electronic version of the journal
(End) Patricia Vannier [CDS] 22-Apr-2016