J/ApJ/866/139 Knots in the deep [FeII]+[SiI] image of the SNR Cas A (Koo+, 2018)
A deep near-infrared [FeII]+[SiI] emission line image of the supernova remnant
Cassiopeia A.
Koo B.-C., Kim H.-J., Lee Y.-H., Raymond J.C., Lee J.-J., Yoon S.-C.,
Moon D.-S.
<Astrophys. J., 866, 139 (2018)>
=2018ApJ...866..139K 2018ApJ...866..139K
ADC_Keywords: Interstellar medium; Supernova remnants; Proper motions;
Infrared sources; Cross identifications; Optical;
Radial velocities
Keywords: ISM: individual objects (Cassiopeia A) ; ISM: supernova remnants ;
supernovae: general
Abstract:
We present a long-exposure (∼10hr), narrowband image of the supernova
(SN) remnant Cassiopeia A (Cas A) centered at 1.644µm emission. The
passband contains [FeII] 1.644µm and [SiI] 1.645µm lines, and
our "deep [FeII]+[SiI] image" provides an unprecedented panoramic view
of Cas A, showing both shocked and unshocked SN ejecta, together with
shocked circumstellar medium at subarcsecond (∼0.7" or 0.012pc)
resolution. The diffuse emission from the unshocked SN ejecta has a
form of clumps, filaments, and arcs, and their spatial distribution
correlates well with that of the Spitzer [SiII] infrared emission,
suggesting that the emission is likely due to [SiI] not [FeII] as in
shocked material. The structure of the optically invisible western
area of Cas A is clearly seen for the first time. The area is filled
with many quasi-stationary flocculi (QSFs) and fragments of the
disrupted ejecta shell. We identified 309 knots in the deep
[FeII]+[SiI] image and classified them into QSFs and fast-moving knots
(FMKs). The comparison with previous optical plates indicates that the
lifetime of most QSFs is ≳60yr. The total H+He mass of QSFs is
∼0.23M☉, implying that the mass fraction of dense clumps in the
progenitor's mass ejection immediately prior to the SN explosion is
about 4%-6%. FMKs in the deep [FeII]+[SiI] image mostly correspond to
S-rich ejecta knots in optical studies, while those outside the
southeastern disrupted ejecta shell appear Fe-rich. The mass of the
[FeII] line emitting, shocked dense Fe ejecta is ∼3x10-5M☉.
Description:
The narrowband [FeII]+[SiI] filter images and H-band images that we
present in this paper were taken with the Wide-Field Camera (WFCAM) on
the UKIRT 3.8m telescope in 2013 September.
Combining all the images obtained with the two arrays results in an
[FeII]+[SiI] image with an effective net exposure time of 10hr and an
H image with 0.8hr. This "deep [FeII]+[SiI] image" has a pixel size of
0.2", and its median PSF is 0.7".
The 1σ uncertainty in astrometry is 0.104" (or 0.52pix).
Objects:
-------------------------------------------------------
RA (ICRS) DE Designation(s)
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23 23 24.00 +58 48 54.0 Cassiopeia A = NAME Cas A
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 89 309 Catalog of knots in the deep [FeII]+[SiI] image
table2.dat 65 42 *Quasi-stationary flocculi (QSFs) with optical
counterparts
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Note on table2.dat: If several optical QSFs are matched with an [FeII] knot,
we use their mean proper motion and velocity.
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See also:
J/ApJ/456/234 : Cas A radio knots spectral indices (Anderson+ 1996)
J/A+A/368/267 : Spatially resolved spectroscopy of Cas A (Maccarone+, 2001)
J/ApJ/613/343 : Cas A knot and filament proper motions (Delaney+, 2004)
J/A+A/475/765 : Fine structure forbidden lines in FeII (Ramsbottom+, 2007)
J/ApJS/179/195 : A catalog of outer ejecta knots in Cas A (Hammell+, 2008)
J/A+A/536/A74 : FeII forbidden lines radiative transition rates (Deb+, 2011)
J/A+A/548/A79 : INTEGRAL-OMC optically var. sources (Alfonso-Garzon+, 2012)
J/ApJ/837/118 : NIR knots in the Cas A supernova remnant (Lee+, 2017)
J/A+A/612/A110 : Cas A LOFAR and VLA images (Arias+, 2018)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 3 I3 --- Seq [1/309] Running sequence number
5 A1 --- f_Seq [a-es] Flag on Seq (1)
7- 8 I2 h RAh [23] Hour of Right Ascension (J2000) (2)
10- 11 I2 min RAm [22/23] Minute of Right Ascension (J2000)
13- 18 F6.3 s RAs Second of Right Ascension (J2000)
20 A1 --- DE- [+] Sign of Declination (J2000) (2)
21- 22 I2 deg DEd [58] Degree of Declination (J2000) (2)
24- 25 I2 arcmin DEm [45/51] Arcminute of Declination (J2000)
27- 31 F5.2 arcsec DEs Arcsecond of Declination (J2000)
33- 37 F5.2 arcsec amaj [0.6/24] Major axis from ellipse fitting
(Dmax)
39- 42 F4.2 arcsec bmin [0.3/6.5] Minor axis from ellipse fitting
(Dmin)
44- 46 I3 deg PA [0/177] Position angle of major axis
(ψellipse) (3)
48- 52 F5.2 arcsec2 Area [0.2/60.5] Area measured from contours
54- 61 A8 mW/m2 Fobs Observed flux; erg/s/cm2
63- 70 A8 mW/m2 Fcor Extinction corrected flux; erg/s/cm2
72- 75 F4.2 arcsec/yr pm [0/0.8]? Proper motion (µ)
77- 82 F6.1 deg theta [-179/180]? Position angle of
proper motion (θµ) (3)
84- 87 A4 --- Class Knot classification (4)
89 A1 --- f_Class [o] Flag on Class (5)
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Note (1): Flag as follows:
a = (Knots 16, 17, 20): No counterpart in 2008, but by comparing with
van den Bergh & Kamper (1983ApJ...268..129V 1983ApJ...268..129V and 1985ApJ...293..537V 1985ApJ...293..537V)
and Alarie+ (2014MNRAS.441.2996A 2014MNRAS.441.2996A), they are classified as QSF
candidates.
b = (Knot 18): No counterpart in 2008 but there is a counterpart
without a positional shift in the HST F098M; this can be a
newly-appearing QSF.
c = (Knots 55, 64, 65, 66): Near the bright QSFs in the
western, disrupted ejecta shell, but classified as FMK candidates
because they are well aligned with the SW jet direction from the
explosion center. The HST F098M image shows no emission features
probably because of large extinction.
d = (Knots 91, 93, 96, 227, 228): The HST F098M image shows emission
features but without a positional shift between the HST and our deep
[FeII]+[SiI] image; thus they are classified as QSF candidates.
e = (Knots 287, 298, 299, 300): Outside of the HST F098M image but the
counterparts with proper motions are confirmed in the HST 2004 image,
so they are classified as FMKs.
s = Knots (QSFs) superposed on the main ejecta shell (see Section 4.3).
Note (2): Central coordinate from ellipse fitting.
Note (3): Measured from north to east.
Note (4): Class as follows:
FMK = "fast-moving knots" (167 occurrences);
QSF = "quasi-stationary flocculi" (94 occurrences);
cFMK = "fast-moving knots" candidates (12 occurrences);
cQSF = "quasi-stationary flocculi" candidates (36 occurrences).
Note (5):
o = QSFs with optical counterparts from Alarie+ (2014MNRAS.441.2996A 2014MNRAS.441.2996A) and
van den Bergh & Kamper (1985ApJ...293..537V 1985ApJ...293..537V).
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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- 3 I3 --- Seq [1/306] Knot identifier
5 A1 --- f_Seq [ac] Flag on Seq (1)
7- 8 I2 h RAh Hour of right ascension (J2000) (2)
10- 11 I2 min RAm Minute of right ascension (J2000)
13- 18 F6.3 s RAs Second of right ascension (J2000)
20 A1 --- DE- Sign of declination (J2000) (2)
21- 22 I2 deg DEd Degree of declination (J2000) (2)
24- 25 I2 arcmin DEm Arcminute of declination (J2000)
27- 31 F5.2 arcsec DEs Arcsecond of declination (J2000)
33- 35 A3 --- A14 Optical identifier
from Alarie+ 2014MNRAS.441.2996A 2014MNRAS.441.2996A (3)
37- 40 I4 km/s RVA14 [-448/107]? Radial velocity from A14
42 A1 --- f_RVA14 [b] Flag on RVA14
44- 45 I2 km/s e_RVA14 [2/58]? RVA14 uncertainty
47- 55 A9 --- V85 Optical identifier
from van den Bergh+ 1985ApJ...293..537V 1985ApJ...293..537V (4)
57- 60 F4.2 arcsec/yr pmV85 [0/0.2]? Proper motion µ from V85
62- 65 I4 km/s RVV85 [-340/432]? Radial velocity from V85
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Note (1): Flag as follows:
a = Knots (QSFs) superposed on the main ejecta shell (see Section 4.3).
b = For QSFs with subknot structures in Alarie+ (2014MNRAS.441.2996A 2014MNRAS.441.2996A),
we use the mean velocity of the subknots.
c = Knot 112: van den Bergh & Kamper (1985ApJ...293..537V 1985ApJ...293..537V) obtained a
large proper motion and put parentheses on the ID, i.e., "(R14)", to
indicate a need for confirmation. But the large proper motion is likely
due to confusion with another fragment in the area. The proper motion
we estimate by comparing with the 2008 image is 0.02"/yr.
Note (2): Central coordinate from ellipse fitting.
Note (3): <[ABD2014] QSF NNa> for Simbad.
Note (4): for Simbad.
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History:
From electronic version of the journal
(End) Prepared by [AAS], Emmanuelle Perret [CDS] 09-Oct-2019