J/ApJS/179/195 A catalog of outer ejecta knots in Cas A (Hammell+, 2008)
A catalog of outer ejecta knots in the Cassiopeia A supernova remnant.
Hammell M.C., Fesen R.A.
<Astrophys. J. Suppl. Ser., 179, 195-208 (2008)>
=2008ApJS..179..195H 2008ApJS..179..195H
ADC_Keywords: Interstellar medium ; Supernova remnants ; Photometry, HST
Keywords: ISM: individual (Cassiopeia A) - ISM: kinematics and dynamics
supernova remnants
Abstract:
Hubble Space Telescope images of the core-collapse supernova remnant
Cassiopeia A are used to identify high-velocity knots of ejecta
located outside the remnant's main emission shell of expanding debris.
These ejecta fragments are found near or ahead of the remnant's
forward shock front and mostly lie from 120" to 300" in radial
distance from the remnant's center of expansion. Filter flux ratios
when correlated with published spectra show that these knots can be
divided into three emission classes: (1) knots dominated by [NII]
λ6548,λ6583 emissions, (2) knots dominated by [OII]
λ7319, λ7330 emissions, and (3) knots displaying filter
flux ratios suggestive of [SII], [OII], and [ArIII] λ7135
emission line strengths similar to the "fast-moving knots" (FMKs)
found in the remnant's bright main shell. Of 1825 knots identified,
444 are strong [NII] emission knots, 192 are strong [OII] emission
knots, and 1189 are FMK-like knots. In terms of location around the
remnant, 972, 207, and 646 knots are found in the remnant's northeast
jet, southwest jet, and non-jet regions, respectively. Assuming a
distance of 3.4kpc, derived knot transverse velocities based on proper
motion measurements spanning a 9 month interval indicate maximum
transverse expansion velocities for these three knot classes of 14500,
13500, and 11500km/s, respectively. We present a catalog of these
outlying ejecta clumps comprising finding charts, epoch 2004.2 knot
positions, proper motions, photometric filter fluxes, and estimated
knot emission type, along with cross-references to previous knot
identifications and data. This compilation represents a nearly tenfold
increase in the number of outlying, high-velocity ejecta knots
identified around the Cassiopeia A remnant.
Description:
High-resolution, multiband images of the Cas A remnant were obtained
on 2004 March 4-6 and December 4-5 using the Wide Field Channel (WFC)
of the Advanced Camera for Surveys (ACS) on board the Hubble Space
Telescope (HST).
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table2.dat 80 1825 Catalog of outlying ejecta knots in Cas A
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See also:
B/hst : HST Archived Exposures Catalog (STScI, 2007)
J/ApJ/456/234 : Cas A radio knots spectral indices (Anderson+ 1996)
J/ApJ/613/343 : Cas A knot and filament proper motions (Delaney+, 2004)
J/A+A/484/755 : Oxygen recombination lines from Cas A knots (Docenko+, 2008)
J/ApJS/174/379 : Optical imaging and spectra of 3C 58 (Fesen+, 2008)
Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
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1- 4 I4 --- [HF2008] Knot identification number
6- 7 I2 h RAh Hour of Right Ascension (J2000) (1)
9- 10 I2 min RAm Minute of Right Ascension (J2000) (1)
12- 16 F5.2 s RAs Second of Right Ascension (J2000) (1)
18 A1 --- DE- Sign of the Declination (J2000) (1)
19- 20 I2 deg DEd Degree of Declination (J2000) (1)
22- 23 I2 arcmin DEm Arcminute of Declination (J2000) (1)
25- 28 F4.1 arcsec DEs Arcsecond of Declination (J2000) (1)
30- 35 F6.2 deg PA Position angle of knot (2)
37- 41 F5.1 arcsec R Radial distance from center (2)
43- 45 I3 mas/yr pm Proper motion (3)
47- 49 A3 --- Type Knot type (4)
51- 56 F6.2 10-20W/m2 F625W ? HST F625W band flux
58- 62 F5.2 10-20W/m2 F775W ? HST F775W band flux
64- 69 F6.2 10-20W/m2 F850LP ? HST F860LP band flux
71- 80 A10 --- C-ID Cross-knot identification or association
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Note (1): Knot positions were measured from ACS/WFC 2004.2 images.
Note (2): PA and R measured with respect to the nominal center of expansion
(Thorstensen, Fesen, & van den Bergh, 2001AJ....122..297T 2001AJ....122..297T) using the
ACS/WFC 2004.2 images. The table is ordered according to PA.
Note (3): Estimated from ACS/WFC 2004.18 and 2004.93 images.
Note (4): Type as follows:
OK = Oxygen Knot;
NK = Nitrogen Knot;
FMK = Fast-Moving Knots.
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History:
From electronic version of the journal
(End) Greg Schwarz [AAS], Emmanuelle Perret [CDS] 18-Sep-2009