J/MNRAS/469/4933 Extended red emission in IC59 and IC63 (Lai+, 2017)
Extended red emission in IC59 and IC63.
Lai T.S.-Y., Witt A.N., Crawford K.
<Mon. Not. R. Astron. Soc., 469, 4933-4948 (2017)>
=2017MNRAS.469.4933L 2017MNRAS.469.4933L (SIMBAD/NED BibCode)
ADC_Keywords: Nebulae ; Photometry
Keywords: radiation mechanisms: non-thermal - dust, extinction -
ISM: individual objects: IC59, IC63 - ISM: lines and bands -
photodissociation region (PDR)
Abstract:
We analysed new wide-field, wide- and narrow-band optical images of
IC 59 and IC 63, two nebulae that are externally illuminated by the
early B-star γ Cas, with the objective of mapping the extended
red emission (ERE), a dust-related photoluminescence process that is
still poorly understood, in these two clouds. The spatial distribution
of the ERE relative to the direction of the incident radiation and
relative to other emission processes, whose carriers and excitation
requirements are known, provides important constraints on the
excitation of the ERE. In both nebulae, we find the ERE intensity to
peak spatially well before the more extended distribution of
mid-infrared emission in the unidentified infrared bands, supporting
earlier findings that point towards far-ultraviolet
(11<Ephoton<13.6eV) photons as the source of ERE excitation. The
band-integrated absolute intensities of the ERE in IC 59 and IC 63
measured relative to the number density of photons available for ERE
excitation are lower by about two orders of magnitude compared to ERE
intensities observed in the high-latitude diffuse interstellar medium.
This suggests that the lifetime of the ERE carriers is significantly
reduced in the more intense radiation field prevailing in IC 59 and IC
63, pointing towards potential carriers that are only marginally
stable against photoprocessing under interstellar conditions. A model
involving isolated molecules or molecular ions, capable of inverse
internal conversion and recurrent fluorescence, appears to provide the
most likely explanation for our observational results.
Description:
We used the 20-inch RC Optical Systems reflector of the Rancho Del Sol
Observatory in Camino, CA, to obtain new, deep images of IC 59 and
IC 63. The images were taken during the time period 2011-8-23 to
2011-9-3. The KAF 16803 CCD (4096x4096-pixels) yielded partially
overlapping square (29.3x29.3arcmin2) images, which fully contained
the two nebulae and adjacent dark sky but excluded the bright
illuminating star γ Cas.
Three Astrodon Generation 2 E-Series filters with nearly square
transmission profiles defined our B, G and R pass bands, with
effective central wavelengths at around 440, 525 and 655nm.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
tablea1.dat 53 88 Regions with measured surface brightness-to-flux
ratio in IC59
tablea2.dat 53 29 Regions with measured-surface-brightness-to-flux
ratio in IC63
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Byte-by-byte Description of file: tablea1.dat tablea2.dat
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Bytes Format Units Label Explanations
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1 I1 h RAh Right ascension (J2000)
3- 4 I2 min RAm Right ascension (J2000)
6- 10 F5.2 s RAs Right ascension (J2000)
12 A1 --- DE- Declination sign (J2000)
13- 14 I2 deg DEd Declination (J2000)
16- 17 I2 arcmin DEm Declination (J2000)
19- 23 F5.2 arcsec DEs Declination (J2000)
25- 28 F4.2 [sr-1] log(S(B)/F*(B)) Measured surface brightness-to-flux
ratio in blue band
30- 33 F4.2 [sr-1] e_log(S(B)/F*(B)) rms uncertainty on log(S(B)/F*(B))
35- 38 F4.2 [sr-1] log(S(G)/F*(G)) Measured surface brightness-to-flux
ratio in green band
40- 43 F4.2 [sr-1] e_log(S(G)/F*(G)) rms uncertainty on log(S(G)/F*(G))
45- 48 F4.2 [sr-1] log(S(R-)/F*(R-)) Measured surface brightness-to-flux
ratio in reddest band
50- 53 F4.2 [sr-1] e_log(S(R-)/F*(R-)) rms uncertainty on log(S(R-)/F*(R-))
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History:
From electronic version of the journal
(End) Patricia Vannier [CDS] 19-Apr-2020