J/A+A/657/A41 Stellar halo of NGC 5128 (Centaurus A) (Rejkuba+, 2022)
The outermost stellar halo of NGC 5128 (Centaurus A): Radial structure.
Rejkuba M., Harris W.E., Greggio L., Crnojevic D., Harris G.L.H.
<Astron. Astrophys. 657, A41 (2022)>
=2022A&A...657A..41R 2022A&A...657A..41R (SIMBAD/NED BibCode)
ADC_Keywords: Galaxies, nearby ; Galaxies, photometry ; Photometry, CCD ;
Optical ; Stars, halo
Keywords: galaxies: elliptical and lenticular, cD -
galaxies: individual: NGC 5128 - galaxies: stellar content
Abstract:
The extended stellar halos of galaxies contain important clues for
investigating their assembly history and evolution.
We investigate the resolved stellar content and the extended halo of
NGC 5128 as a function of galactocentric distance, and trace the halo
outward to its currently detectable limits.
We used Hubble Space Telescope images obtained with the WFPC2, ACS,
and WFC3 cameras equipped with F606W and F814W filters to resolve
individual red giant branch (RGB) stars in 28 independent pointings
across the halo of NGC 5128. The stellar halo analysis for 14 of these
pointings is presented here for the first time. Star counts from deep
VI color-magnitude diagrams reaching at least 1.5mag below the tip of
the RGB are used to derive the surface density distribution of the
halo. The contamination by Milky Way stars is assessed with a new
control field, with models, and by combining optical and near-IR
photometry.
We present a new calibration of the WFC3 F606W + F814W photometry
to the ground-based VI photometric system. The photometry shows that
the stellar halo of NGC 5128 is dominated by old RGB stars that are
present in all fields. The V-band surface brightness of fields changes
from 23 to 32mag/arcsec2 between the innermost field only 8.3kpc
from the galaxy center to our outermost halo fields, which are located
140 kpc away from the center along the major axis and 92 kpc along the
minor axis. Within the inner ∼30kpc, we also find evidence for a
2-3Gyr old population traced by asymptotic giant branch stars that are
brighter than the tip of the RGB. This population contributes only up
to 10% in total stellar mass if it is 2Gyr old, but a larger fraction
of 30-40% is required if its age is 3Gyr. The stellar surface density
profile is well fit by a classic r1/4 curve or a simple power-law
form ∼r-3.1 over the full radial range, with no obvious break in the
slope, but with large field-to-field scatter. The ellipticity measured
from integrated-light photometry in the inner parts, e=(b/a)=0.77,
flattens to e=0.54±0.02 beyond 30kpc. Considering the flattening of
the outer halo, the projection of the elliptical isophote on the
semimajor axis for our most distant field reaches nearly 30 effective
radii.
Description:
Photometric catalog of 237,602 stellar-like objects detected in 30
fields located within the extended stellar halo of NGC 5128, including
a control field F10A.
Observations were carried out with the Hubble Space Telescope using
different camera. The file fields.dat lists for each pointing the RA
and DEC coordinates of the field center along with the foreground
reddening value E(B-V) at that location and the HST camera used to
take data.
The PSF fitting photometry has been performed retaining only
stellar-like objects and magnitudes are calibrated to the ground-based
VI Johnson-Cousins VEGAMAG photometric system. For each field, after
the field identifier the total calibrated magnitudes in V and I-band
and the photometric measurement errors are given for all detected
stellar sources. Catalog magnitudes do not include correction for
interstellar extinction.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
fields.dat 54 30 Field IDs, coordinates, E(B-V) and instrument
catalog.dat 46 237602 Photometry for stellar sources in 30 fields
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See also:
J/A+A/369/812 : NGC 5128 globular clusters UVKs photometry (Rejkuba, 2001)
J/A+A/406/75 : JHKs magnitudes of variables in NGC 5128 (Rejkuba+, 2003)
J/A+A/447/71 : CHANDRA X-ray point sources in Cen A (NGC 5128) (Voss+, 2006)
J/A+A/574/A109 : Spectroscopy of Planetary Nebulae in NGC 5128 (Walsh+, 2015)
J/ApJ/600/716 : NGC 5128 Chandra X-ray point sources (Minniti+, 2004)
J/AJ/134/494 : NGC 5128 globular clusters UBVRICMT1 phot. + RV
(Woodley+, 2007)
J/ApJ/805/65 : NGC 5128 globular clusters FLAMES observations (Taylor+, 2017)
Byte-by-byte Description of file: fields.dat
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Bytes Format Units Label Explanations
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1- 4 A4 --- FieldID Field pointing identifier (FNNA or WNN)
12- 13 I2 h RAh Right ascension (J2000.0)
15- 16 I2 min RAm Right ascension (J2000.0)
18- 19 I2 s RAs Right ascension (J2000.0)
22 A1 --- DE- Declination sign (J2000.0)
23- 24 I2 deg DEd Declination (J2000.0)
26- 27 I2 arcmin DEm Declination (J2000.0)
29- 30 I2 arcsec DEs Declination (J2000.0)
34- 38 F5.3 mag E(B-V) Galactic reddening (1)
40- 54 A15 --- Inst Instrument
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Note (1): Foreground reddening value toward the field center according to
Schlegel et al. (1998ApJ...500..525S 1998ApJ...500..525S).
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Byte-by-byte Description of file: catalog.dat
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Bytes Format Units Label Explanations
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1- 4 A4 --- FieldID Field pointing identifier (FNNA or WNN)
15- 20 F6.3 mag Vmag V-band magnitude without correction
for galactic extinction
24- 28 F5.3 mag e_Vmag V-band magnitude measurement error
33- 38 F6.3 mag Imag I-band magnitude without correction
for galactic extinction
42- 46 F5.3 mag e_Imag I-band magnitude measurement error
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Acknowledgements:
Marina Rejkuba, mrejkuba(at)eso.org
(End) Marina Rejkuba [ESO, Germany], Patricia Vannier [CDS] 08-Nov-2021