J/MNRAS/493/4463 Crystalline silicate absorption at 11.1µm (Do-Duy+, 2020)
Crystalline silicate absorption at 11.1µm: ubiquitous and abundant in
embedded YSOs and the interstellar medium.
Do-Duy T., Wright C.M., Fujiyoshi T., Glasse A., Siebenmorgen R., Smith R.,
Stecklum B., Sterzik M.
<Mon. Not. R. Astron. Soc., 493, 4463-4517 (2020)>
=2020MNRAS.493.4463D 2020MNRAS.493.4463D (SIMBAD/NED BibCode)
ADC_Keywords: YSOs ; Interstellar medium ; H II regions ; Spectra, infrared
Keywords: (stars:) circumstellar matter - stars: protostars -
(ISM:) dust, extinction - ISM: evolution
Abstract:
Utilizing several instruments on 4-8m telescopes, we have observed a
large sample of objects in the mid-infrared (8-13µm). These
comprise a few evolved stars, multiple envelopes of embedded young
stellar objects (YSOs) or compact H-II regions, and several sightlines
through the interstellar medium (ISM). The latter is where dust
resides - and is potentially modified - between its formation in
evolved stellar outflows and deposition in molecular clouds. In most
objects, we detect not only the well-known 9.7µm absorption feature
of amorphous silicates but also a second absorption band around
11.1µm whose carrier is attributed to crystalline forsterite. We
propose that crystalline silicates are essentially ubiquitous in the
ISM and earliest phases of star formation, and are evolutionary
precursors to T-Tauri and Herbig stars where such silicates have been
commonly found. Modelling shows that in most YSOs, H-II regions and
ISM cases, the forsterite mass fraction is between 1 and 2 per cent,
suggesting that the younger phases inherit their abundance from the
ISM. However, several sources show much stronger features (abundances
≥3 per cent). This suggests that significant processing, perhaps
crystallization by thermal annealing, occurs early on in star
formation. Most intriguing is the first detection of crystalline
silicate in the diffuse ISM. We propose that our observed abundance is
consistent with a mass fraction of crystalline silicates of 10-20 per
cent injected into the ISM, along with commonly accepted lifetimes
against their destruction, but only if cosmic ray-induced
amorphization is insignificant over a few Giga years.
Description:
The 8-13µm spectra presented here were obtained using several
different instruments principally between 2002 and 2007. These include
the mid-infrared (MIR) long-slit spectrometers T-ReCS at the
Gemini-South telescope (under programme GS-2006B-Q-81) and Michelle at
both the UKIRT and Gemini-North telescopes (under programme
GN-2005B-Q-83), TIMMI2 on the ESO 3.6m telescope, and COMICS on the
Subaru telescope. The TIMMI2 and Michelle-on-UKIRT data were collected
in the spectropolarimetric mode of those instruments, but only the
conventional spectrum (Stokes I) is presented here.
The spectral resolution was in the range of 100-200 for all
instruments, with slit widths of 0.7arcsec for T-ReCS, 0.4arcsec for
Michelle on Gemini, 0.64 or 1.28arcsec for Michelle on UKIRT, 3arcsec
for TIMMI2, and 0.33arcsec for COMICS. Standard chopping and nodding
were implemented. Technical parameters of all our observations are
listed in Table 1.
File Summary:
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FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
table1.dat 99 93 Observation log
table2.dat 149 28 Comparisons of optical depths at different
wavelengths
table3.dat 84 57 Asymmetric Gaussian fit parameters for the
11.1um feature and independent estimates of
τ9.7
table5.dat 77 53 Mass fraction (per cent) of each component over
the total mass of the silicate dust in the
spectral fits
table8.dat 84 13 Optically thin model - mass fraction (per cent)
and χ2 for each spectral fit
refs.dat 76 34 References for Table 2
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Byte-by-byte Description of file: table1.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 14 A14 --- Name Source name
16 A1 --- n_Name [*+] Note on Name (1)
18 A1 --- f_Name [EYS] Flag on Name (G1)
20- 30 A11 --- Date Date of observation
32- 43 A12 --- Inst Instrument used for the observation (2)
45- 49 F5.1 deg PAslit Slit position angle
51- 54 F4.1 arcsec Chop Chop throw
56- 60 F5.1 deg Nod Nod throw
62- 72 A11 --- StdStar Standard star
74- 77 F4.2 --- AirmassSrc Airmass of the source
79- 82 F4.2 --- AirmassStd Airmass of the standard star
84- 92 A9 --- ISOID ISO identifier
94- 99 A6 --- Type Type of the object (3)
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Note (1): Note as follows:
* = S140 IRS3 has been previously reported as an IR triple at the K band by
Preibisch et al. (2001A&A...378..539P 2001A&A...378..539P) but to our knowledge not
previously resolved in the mid-IR. The notation of Preibisch et al.
(2001A&A...378..539P 2001A&A...378..539P) is used here, where IRS3a and IRS3b are separated
by 0.63arcsec along a position angle of 85°. The Michelle
acquisition image shows them to be similarly bright. The slit was set
to a position angle of 74° to include IRS1 and IRS3 but some flux
from IRS3b is probably lost in the 0.4arcsec-wide slit.
+ = S255 NIRS1 and NIRS3 are components of an IR double separated by about
2.5arcsec along a position angle of 104°. We use the notation of
Tamura et al. (1991ApJ...378..611T 1991ApJ...378..611T), in which NIRS1 is the brightest
K-band source. NIRS3 is the brightest at L-, N-, and Q-band source
(Beichman, Becklin & Wynn-Williams 1979ApJ...232L..47B 1979ApJ...232L..47B; Itoh et al.
2001PASJ...53..495I 2001PASJ...53..495I; Longmore et al. 2006MNRAS.369.1196L 2006MNRAS.369.1196L; de Wit et al.
2009A&A...494..157D 2009A&A...494..157D), and the more deeply embedded (this work).
Note (2): For those targets observed with Michelle, the letter in brackets
refers to the telescope, G for Gemini and U for UKIRT. In some cases,
especially for the TIMMI2 observations, multiple independent spectra
of the same target were taken on the same night.
Note (3): Object type as follows:
OH/IR = OH/IR star
ES = Embedded YSO
ISM = Interstellar medium
DISM = Diffuse interstellar medium
HII = H-II region
MC = Molecular cloud
HE = Herbig Ae/Be star
FU = FU Orionis object
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Byte-by-byte Description of file: table2.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 14 A14 --- Name Source name
16 A1 --- f_Name [YI] Flag on Name (1)
18- 22 F5.3 --- tau11.1 ? Optical depth at 11.1um
24- 28 F5.3 --- e_tau11.1 ? Error on tau11.1
30- 33 F4.2 --- tau3.0 ? Optical depth at 3.0um
35- 38 F4.2 --- e_tau3.0 ? Error on tau3.0
40- 44 F5.3 --- tau3.25 ? Optical depth at 3.25um
46- 50 F5.3 --- e_tau3.25 ? Error on tau3.25
52- 56 F5.3 --- tau3.4 ? Optical depth at 3.4um
58- 62 F5.3 --- e_tau3.4 ? Error on tau3.4
64- 68 F5.3 --- tau3.47 ? Optical depth at 3.47um
70- 75 F6.4 --- e_tau3.47 ? Error on tau3.47
77- 80 F4.2 --- tau4.27 ? Optical depth at 4.27um
82- 85 F4.2 --- e_tau4.27 ? Error on tau4.27
87- 90 F4.2 --- tau6.0 ? Optical depth at 6.0um
92- 96 F5.3 --- e_tau6.0 ? Error on tau6.0
98 A1 --- l_tau6.2 Limit flag on tau6.2
100-104 F5.3 --- tau6.2 ? Optical depth at 6.2um
106-110 F5.3 --- e_tau6.2 ? Error on tau6.2
112-116 F5.3 --- tau6.85 ? Optical depth at 6.85um
118-122 F5.3 --- e_tau6.85 ? Error on tau6.85
124-127 F4.2 --- B_tau6.85 ? Upper bound on tau6.85
129-149 A21 --- Ref References
--------------------------------------------------------------------------------
Note (1): Flag as follows:
Y = Embedded young stellar objects and other youthful sources
I = ISM paths to the GC and Wolf-Rayet stars
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Byte-by-byte Description of file: table3.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 14 A14 --- Name Source name
16- 17 A2 --- Inst Intrument used (G2)
19 A1 --- f_Name [EYS] Flag on Name (G1)
21- 25 F5.3 --- tau11.1 ? Optical depth at 11.1um
27 A1 --- f_tau11.1 [e] Flag on tau11.1 (1)
29- 33 F5.3 --- e_tau11.1 ? Error on tau11.1
35- 39 F5.2 um lambdac ? Central wavelength of the 11.1um feature
41- 44 F4.2 um e_lambdac ? Error on lambdac
46- 49 F4.2 um FWHM ? FWHM of the 11.1um feature
51- 54 F4.2 um e_FWHM ? Error on FWHM
56- 59 F4.2 --- tau9.7ap ? Optical depth at 9.7um evaluated by
eyeball estimation
61- 64 F4.2 --- e_tau9.7ap ? Error on tau9.7ap
66- 69 F4.2 --- tau9.7bf ? Optical depth at 9.7um evaluated by the
best fit with optically thick model
71- 74 F4.2 --- e_tau9.7bf ? Error on tau9.7bf
76- 79 F4.2 --- tau9.7ot ? Optical depth at 9.7um evaluated by the
best fit with optically thin model
81- 84 F4.2 --- e_tau9.7ot ? Error on tau9.7ot
--------------------------------------------------------------------------------
Note (1): The 11.1um feature is in emission for R Mon
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Byte-by-byte Description of file: table5.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 14 A14 --- Name Source Name
16- 17 A2 --- Inst Intrument used (G2)
19 A1 --- f_Name [EYS] Flag on Name (G1)
21- 24 F4.1 % Olisg ? Mass fraction of small grain Olivine
(0.1um)
26- 28 F3.1 % e_Olisg ? Error on Olisg
30- 33 F4.1 % Olilg ? Mass fraction of large grain Olivine (2um)
35- 37 F3.1 % e_Olilg ? Error on Olilg
39- 42 F4.1 % Pyrsg ? Mass fraction of small grain Pyroxene
(0.1um)
44- 46 F3.1 % e_Pyrsg ? Error on Pyrsg
48- 51 F4.1 % Pyrlg ? Mass fraction of large grain Pyroxene (2um)
53- 56 F4.1 % e_Pyrlg ? Error on Pyrlg
58- 60 F3.1 % Fors Mass fraction of 0.1um-grain Forsterite
62- 64 F3.1 % e_Fors Error on Fors
66- 68 F3.1 % Enst ? Mass fraction of 0.1um-grain Enstatite
70- 72 F3.1 % e_Enst ? Error on Enst
74- 77 F4.2 % chi2 Reduced chi-squared of the spectral fit
--------------------------------------------------------------------------------
Byte-by-byte Description of file: table8.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 14 A14 --- Name Source name
16- 17 A2 --- Inst Intrument used (G2)
19 A1 --- f_Name [EYO] Flag on Name (1)
21- 24 F4.1 % Olisg Mass fraction of small grain Olivine (0.1um)
26- 29 F4.1 % e_Olisg Error on Olisg
31- 34 F4.1 % Olilg ? Mass fraction of large grain Olivine (2um)
36- 39 F4.1 % e_Olilg ? Error on Olilg
41- 44 F4.1 % Pyrsg Mass fraction of small grain Pyroxene (0.1um)
46- 49 F4.1 % e_Pyrsg Error on Pyrsg
51- 53 F3.1 % Pyrlg ? Mass fraction of large grain Pyroxene (2um)
55- 58 F4.1 % e_Pyrlg ? Error on Pyrlg
60- 62 F3.1 % Fors Mass fraction of 0.1um-grain Forsterite
64- 66 F3.1 % e_Fors Error on Fors
68- 70 F3.1 % Enst ? Mass fraction of 0.1um-grain Enstatite
72- 74 F3.1 % e_Enst ? Error on Enst
76- 79 F4.2 % chi2thin Reduced chi-squared of the optically thin
model spectral fit
81- 84 F4.2 % chi2thick ? Reduced chi-squared of the optically thick
model spectral fit (same as Table 5)
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Note (1): Flag as follows:
E = Evolved source (stellar outflow = dust factory)
Y = Young source (molecular cloud, circumstellar envelope or disc,
HII region = dust repository)
O = Young source that do not require crystalline silicate
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Byte-by-byte Description of file: refs.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 2 I2 --- Ref [1/34] Reference number
4- 22 A19 --- BibCode BibCode
24- 57 A34 --- Aut Author's name
59- 76 A18 --- Com Comments
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Global Notes:
Note (G1): Flag as follows:
E = Evolved source (stellar outflow = dust factory)
Y = Young source (molecular cloud, circumstellar envelope or disc = dust
repository)
S = Sightline through dense and/or diffuse ISM = (dust residence)
Note (G2): Instrument as follows:
MI = observed with Michelle
UK = observed with Michelle on UKIRT
TR = observed with T-ReCS
TI = observed with TIMMI2
CO = observed with COMICS
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History:
From electronic version of the journal
(End) Ana Fiallos [CDS] 02-May-2023