J/ApJ/899/14 Optical & FeII sources in Supernova remnant with HST (Long+, 2020)
The Supernova Remnant Population of NGC 6946 as Observed in [FeII] 1.644um with
HST.
Long K.S., Blair W.P., Winkler P.F., Lacey C.K.
<Astrophys. J., 899, 14 (2020)>
=2020ApJ...899...14L 2020ApJ...899...14L
ADC_Keywords: Supernova remnants; Interstellar medium; Photometry, HST; Optical;
Infrared
Keywords: Supernova remnants ; Interstellar medium
Abstract:
NGC6946 is a high-star-formation-rate, face-on, spiral galaxy that has
hosted 10 supernovae since 1917. Not surprisingly, a large number of
supernova remnants and candidates have been identified either as
optical nebulae with high [SII]:Hα line ratios (147) or as
compact non-thermal radio sources (35). However, there are only seven
overlaps between these two samples. Here, we apply [FeII] 1.644µm
emission as a new diagnostic to search for supernova remnants in an
attempt to resolve this discrepancy. [FeII] is expected to be
relatively strong in the radiative shocks of supernova remnants and
almost absent in HII regions. It is less susceptible to the effects of
absorption along the line of sight than the optical lines normally
used to identify remnants. Using data from the WFC3 camera on Hubble
Space Telescope (HST), we identify 132 [FeII] emission nebulae in
NGC6946 as likely supernova remnants. Of these, 54 align with
previously known optical supernova remnants. The remaining 78 objects
are new; of these 44 are visible in new HST imagery in Hα and
[SII]. This brings the total number of supernova remnant candidates
(from optical and/or IR data) in NGC6946 to 225. A total of 14
coincidences with radio supernova remnant candidates (out of 30 in our
search area) are found in this expanded list. The identification of so
many new remnant candidates validates the use of [FeII] imagery for
finding remnants, and suggests that previous remnant searches in other
galaxies may be far from complete.
Description:
The primary observations for this project (Program ID 14638, Long-PI)
took place on 2016 October 26-28 and were carried out with the IR
camera on Hubble Space Telescope (HST)'s Wild Field Camera 3 (WFC3).
The observations comprised a 3x3 mosaic of pointings, covering most of
the inner parts of the galaxy. Each field of the mosaic was imaged in
[FeII] with the F164N filter for 2400s and in an overlapping continuum
band with the F160W filter for 600s, both in a single orbit.
In order to carry out the project, we have also made use of
observations of NGC6946 (Program ID 15216, Blair-PI) made with the
UVIS camera on WFC3, using the F657N (Hα+[NII]), F673N ([SII])
and F547M continuum filters. Comprising seven overlapping fields, the
coverage for these data is shown in green in Figure1. The WFC3 UVIS
data were obtained on 2019 January 25-27. Each of the seven fields was
observed for 2826s in F657N, 3853s in F673N, and 1473s in F547M.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 93 132 [FeII] sources
table2.dat 74 147 Optical SNRs
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See also:
I/345 : Gaia DR2 (Gaia Collaboration, 2018)
J/ApJS/177/465 : X-ray variability in NGC 6946, NGC 4485/90 (Fridriksson+,2008)
J/ApJ/788/55 : HST/WFC3 SNR discoveries in M83 (NGC5236) (Blair+, 2014)
J/ApJ/855/140 : MMT spectra of SNRs and SNR candidates in M33 (Long+, 2018)
J/ApJ/875/85 : Optical search SNRs in NGC6946 with WIYN & GMOS (Long+, 2019)
J/ApJ/875/136 : BVRI, spectra & IR obs. of type II-P SN2017eaw (Van Dyk+,2019)
J/ApJ/881/54 : Masses of SNR progenitors in M83 (Williams+, 2019)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 7 A7 --- Name Identifier
9- 10 I2 h RAh [20] Hour of Right Ascension (J2000)
12- 13 I2 min RAm [34/35] Minute of Right Ascension (J2000)
15- 19 F5.2 s RAs Second of Right Ascension (J2000)
21 A1 --- DE- [+] Sign of declination (J2000)
22- 23 I2 deg DEd [60] Degree of Declination (J2000)
25- 26 I2 arcmin DEm [5/12] Arcminute of Declination (J2000)
28- 31 F4.1 arcsec DEs Arcsecond of Declination (J2000)
33- 34 I2 pc Dist [6/49] Distance
36- 38 F3.1 kpc R [0.1/8.2] Galactic distance
40- 44 F5.1 10-17mW/m2 FFe [3.1/415] [FeII] flux; 1e-17erg/s/cm2
46- 49 F4.1 10-17mW/m2 e_FFe [0.2/49] Uncertainty in FFe
51- 55 F5.1 10-17mW/m2 FPaB [-19/352]? PaΒ flux; 1e-17erg/s/cm2 (1)
57- 60 F4.1 10-17mW/m2 e_FPaB [0.2/32.7]? Uncertainty in FPaB
62 A1 --- Env Environment code (2)
64- 70 A7 --- Opt Optical detection identifier (3)
72- 78 A7 --- Rad Radio detection identifier (5)
80- 85 A6 --- Bru Bruursema+, 2014AJ....148...41B 2014AJ....148...41B survey
identifier <L19 => [LWB2019] NNN> (3)
87- 93 A7 --- X-ray X-ray detection identifier (4)
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Note (1): A negative flux implies that the average count rate in the source
region was less than that in the chosen background region.
Note (2): If labeled C, the [Fe II] sources is in a relatively complex
region with extended Hα and/or PaΒ See text.
Note (3): Labels as follows:
L19 = Long+, 2019, J/ApJ/875/85
L97 = Lacey & Duric, 2001ApJ...560..719L 2001ApJ...560..719L
F08 = Fridriksson+, 2008, J/ApJS/177/465
Note (4): A trailing colon indicates that while a radio or X-ray source was
within 2" of the [FeII] source. While close, the positional match
was not as precise as most of the rest of the sample source, the
positional match was not as close as most of the rest of the sample.
<[FHL2008] NGC 6946 NN>
Note (5): There are two catalog sources, L20-20 and L20-22 associated with
the radio source L97-26. <[LDG97] NNN>
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Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 7 A7 --- Name Identifier
9- 10 I2 h RAh [20] Hour of Right Ascension (J2000)
12- 13 I2 min RAm [34/35] Minute of Right Ascension (J2000)
15- 19 F5.2 s RAs Second of Right Ascension (J2000)
21 A1 --- DE- [+] Sign of declination (J2000)
22- 23 I2 deg DEd [60] Degree of Declination (J2000)
25- 26 I2 arcmin DEm [4/13] Arcminute of Declination (J2000)
28- 31 F4.1 arcsec DEs Arcsecond of Declination (J2000)
33- 35 I3 pc Dist [12/337] Distance
37- 40 F4.1 kpc R [0.2/13.3] Galactic distance
42- 44 A3 --- Conf Confirmed (1)
46- 52 A7 --- FeIIcat The [FeII] catalog (2)
54- 58 F5.1 10-17mW/m2 FFe [-5.3/415]? [FeII] flux; 1e-17erg/s/cm2
(3)
60- 63 F4.1 10-17mW/m2 e_FFe [0.4/49]? Uncertainty in FFe
65- 69 F5.1 10-17mW/m2 FPaB [-11.1/59.1]? Paβ flux;
1e-17erg/s/cm2 (3)
71- 74 F4.1 10-17mW/m2 e_FPaB [0.3/14.0]? Uncertainty in FPaB
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Note (1): Note as follows:
yes = spectroscopically confirmed to have [SII]:Hα>0.4
no = spectroscopic observation was made, but the ratio was lower than 0.4.
Note (2): If in the [FeII] catalog, the name of the object is given.
Entries labeled "no" indicate objects that are not in the [FeII]
catalog but that are in the region observed in [FeII].
Note (3): A negative flux implies that the average count rate in the source
region was less than that in the chosen background region. Values
for [FeII] catalog objects are the same as in Table 1.
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History:
From electronic version of the journal
(End) Prepared by [AAS], Coralie Fix [CDS], 12-Oct-2021