J/A+A/620/A52 DIB properties in lines of sight to M17 (Ramirez-Tannus+, 2018)
Diffuse interstellar bands in the HII region M17:
Insights into their relation with the total-to-selective visual extinction RV.
Ramirez-Tannus M.C., Cox N.L.J., Kaper L., de Koter A.
<Astron. Astrophys. 620, A52 (2018)>
=2018A&A...620A..52R 2018A&A...620A..52R (SIMBAD/NED BibCode)
ADC_Keywords: Star Forming Region ; Stars, pre-main sequence ; YSOs ;
Stars, OB ; Interstellar medium
Keywords: dust: extinction - HII regions - ISM: lines and bands
Abstract:
Diffuse interstellar bands (DIBs) are broad absorption features
measured in sightlines probing the diffuse interstellar medium.
Although large carbon-bearing molecules have been proposed as the
carriers producing DIBs, their identity remains unknown. DIBs make an
important contribution to the extinction curve; the sightline. to the
young massive star-forming region M17 shows anomalous extinction in
the sense that the total-to-selective extinction parameter (RV)
differs significantly from the average Galactic value and may reach
values RV>4. Anomalous DIBs have been reported in the sightline
towards Herschel 36 (RV=5.5), in the massive star-forming
region M8. Higher values of RV have been associated with a
relatively higher fraction of large dust grains in the line of sight.
Given the high RV values, we investigate whether the DIBs in
sightlines towards young OB stars in M17 show a peculiar behaviour.
We measure the properties of the most prominent DIBs in M17 and study
these as a function of E(B-V) and RV. We also analyse the
gaseous and dust components contributing to the interstellar
extinction.
The DIB strengths in M17 concur with the observed relations between
DIB equivalent width and reddening E(B-V) in Galactic sightlines. For
several DIBs we discover a linear relation between the normalised DIB
strength EW/AV and RV-1. These trends suggest two groups of
DIBs: (i) a group of ten moderately strong DIBs that show a
sensitivity to changes in RV that is modest and proportional to DIB
strength, and (ii) a group of four very strong DIBs that react
sensitively and to a similar degree to changes in RV, but in a way
that does not appear to depend on DIB strength.
DIB behaviour as a function of reddening is not peculiar in sightlines
to M17. Also, we do not detect anomalous DIB profiles like those seen
in Herschel 36. DIBs are stronger, per unit visual extinction, in
sightlines characterised by a lower value of RV, i.e. those
sightlines that contain a relatively large fraction of small dust
particles. New relations between extinction normalised DIB strengths,
EW/AV, and RV support the idea that DIB carriers and interstellar
dust are intimately connected. Furthermore, given the distinct
behaviour of two groups of DIBs, different types of carriers do not
necessarily relate to the dust grains in a similar way.
Description:
Table 3. DIB properties in the lines of sight to M17. Column 1 shows
the rest wavelength of the DIBs. Columns 3 to 5 show the FWHM (nm)
and EW (mÅ) measured for the sightlines towards the objects in M17.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 90 11 Extinction properties measured in the sight
lines towards M17
table3.dat 24 154 DIB EW and FWHM towards M17 sightlines
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See also:
J/A+A/604/A78 : M17 massive pms stars X-shooter spectra (Ramirez-Tannus+, 2017)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 4 A4 --- Id Identifier, BNNN (Cl* NGC 6618 B NNN in Simbad)
6- 14 A9 --- SpType Spectral type from Paper I
16- 20 F5.2 mag Bmag ?=- B magnitude
21 A1 --- r_Bmag [bcd] Reference for B mag (1)
23- 27 F5.2 mag Vmag ?=- V magnitude
28 A1 --- r_Vmag [bcd] Reference for Vmag (1)
30- 35 F6.3 mag Kmag 2MASS (Cat. II/246) K magnitude
37- 39 F3.1 mag RvSED Total-to-selective visual extinction RV
derived by fitting the spectral energy
distribution to Kurucz models
41- 43 F3.1 mag E_RvSED ? Error on RvSED (upper value)
45- 47 F3.1 mag e_RvSED Error on RvSED (lower value)
49- 52 F4.2 mag RVFitzp ? Total-to-selective visual extinction RV
derived using Eq (1) (see Sect. 3)
54- 57 F4.1 mag AVSED V-band colour excess AV derived by fitting
the spectral energy distribution to
Kurucz models
59- 61 F3.1 mag E_AVSED ? Error on AVSED (upper value)
63- 65 F3.1 mag e_AVSED Error on AVSED (lower value)
67- 70 F4.2 mag AV ? V-band colour excess AV (2)
72- 75 F4.2 mag E(B-V)SED Extinction parameter E(B-V)=AV/Rv derived by
fitting the spectral energy distribution to
Kurucz models
77- 80 F4.2 mag e_E(B-V)SED rms uncertainty on E(B-V)SED
82- 85 F4.2 mag E(B-V) ? Colour excess (B-V)-(B-V)0 (2)
87- 90 F4.2 mag AK ? Extinction parameter AK derived using
Eq (1) (see Sect. 3)
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Note (1): Reference as follows:
b = AAVSO Photometric all sky survey (APASS) catalog:
https://www.aavso.org/apass
c = Chini et al. (1980A&A....91..186C 1980A&A....91..186C)
d = Hoffmeister et al. (2008ApJ...686..310H 2008ApJ...686..310H)
Note (2): where the intrinsic colour (B-V)0 is taken from
Pecaut & Mamajek (2013, Cat. J/ApJS/208/9) and
Wegner (2000MNRAS.319..771W 2000MNRAS.319..771W, 2014AcA....64..261W 2014AcA....64..261W).
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Byte-by-byte Description of file: table3.dat
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Bytes Format Units Label Explanations
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1- 4 A4 --- Id Identifier, BNNN
6- 10 I5 0.1nm lambda Central wavelength of DIB
12- 15 F4.2 nm FWHM ?=- Full width at half maximum
17- 20 I4 0.1pm EW ?=- Equivalent width
22- 24 I3 0.1pm e_EW ?=- Error on the measurement of EW
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Acknowledgements:
Maria Claudia Ramirez-Tannus, m.c.ramireztannus(at)uva.nl
References:
Ramirez-Tannus et al., Paper I 2017A&A...604A..78R 2017A&A...604A..78R, Cat. J/A+A/604/A78
(End) Patricia Vannier [CDS] 03-Oct-2018