J/A+A/672/A181 Early-type stars DIB in optical and infrared (Smoker+, 2023)
A high-resolution study of near-IR diffuse interstellar bands, search for
small-scale structure, time variability, and stellar features.
Smoker J.V., Mueller A., Monreal Ibero A., Elyajouri M., Evans C.J.,
Najarro F., Farhang A., Cox N.L.J., Minniti J., Smith K.T., Pritchard J.,
Lallement R., Smette A., Boffin H.M.J., Cordiner M., Cami J.
<Astron. Astrophys. 672, A181 (2023)>
=2023A&A...672A.181S 2023A&A...672A.181S (SIMBAD/NED BibCode)
ADC_Keywords: Stars, early-type ; Stars, emission ; Abundances ; Infrared ;
Optical ; Interstellar medium
Keywords: ISM: clouds - ISM: lines and bands - ISM: molecules -
dust, extinction - stars: early type - stars: emission line, Be
Abstract:
The diffuse interstellar bands (DIBs) are a set of hundreds of
unidentified absorption features that appear almost ubiquitously
throughout the interstellar medium. Most DIBs appear at optical
wavelengths, but some are in the near-infrared.
We aim to characterise near-infrared DIBs at high spectral resolving
power towards multiple targets.
We observed 76 early-type stars at a resolving power of 50000
(velocity resolution ∼6km/s) and signal-to-noise ratios of several
hundreds using the CRyogenic high-resolution InfraRed Echelle
Spectrograph (CRIRES). These data allow us to investigate the DIBs
around 1318.1, 1527.4, 1561.1, 1565.1, 1567.0, 1574.4, and 1624.2nm.
We detected a total of six DIB features and 17 likely stellar features
through comparisons with a model spectrum computed with cmfgen.
Additionally, we measured equivalent widths of the DIBs at 1318.1 and
1527.4nm using observations with X-shooter towards ten very highly
reddened (3.2<E(B-V)<6.5) Cepheid variable stars and towards four
stars observed at low values of precipitable water vapour as well as
by using other archive data. Results: We measured correlations
(correlation coefficient r∼0.73-0.96, depending on the subsample used)
between DIB equivalent width and reddening for the DIBs at 1318.1,
1561.1, 1565.1, and 1567.0nm. Comparing the near-infrared DIBs with 50
of the strongest optical DIBs, we find correlations r≳0.8 between the
1318, 1527, 1561, 1565, and 1567nm and the optical DIBs 5705, 5780,
6203, 6283, and 6269Å. The 5797Å, DIB is less well correlated
with the near-infrared DIBs. The DIB at 9632.1Å, which is likely
C60+, is not well correlated with the 1318.1nm DIB. Partial
correlation coefficients using E(B-V) as the covariate were also
determined. For stars earlier than B2, the 1318.1nm DIB is affected by
an emission line on its blue wing that is likely stellar in nature,
although we cannot rule out an interstellar or circumstellar origin
for this line caused by, for example, a DIB in emission. The 1318.1nm
DIB also has an extended red wing. The line is reasonably well fitted
by two Gaussian components, although neither the component equivalent
width (EW) ratios nor the separation between components are obviously
correlated with such indicators as λλ5780/5797 and
reddening. The EW at 1318nm correlates with HI with EW(1318nm)/E(B-V)
decreasing with f(H2).
Five pairs of stars within one arcmin of each other show very similar
1318.1∼nm DIB profiles. Possible variation in the 1318.1nm feature is
seen between HD 145501 and HD 145502 (separated by 41-arcsec,
equivalent to 7200au) and HD 168607 and HD 168625 (separated by
67-arcsec, equivalent to 0.52pc on the plane of the sky). Seventeen
sightlines have repeat CRIRES observations separated by six to 14
months, and two sightlines have repeat X-shooter observations
separated by 9.9 years. No time variability was detected in the
1318.1nm DIB in the CRIRES data nor in the 5780.5, 5797.1, 1318.1, and
1527.4nm DIBs. Tentative time variation is observed in the C60+
DIBs at 9577 and 9632Å, towards HD 183143, although it is very
close to the noise level and requires confirmation.
The Near Infrared (NIR) DIBs observed occur more in more UV-irradiated
regions than the 5797Å, DIB allowing the study of heavily reddened
sightlines. Future searches for time variability in DIBs will require
either higher quality data, larger intervals between epochs, or both.
Description:
We present equivalent widths of a number of diffuse interstellar bands
in the optical and infrared. Correlation plots for values of Pearson
correlation coefficient exceeding 0.87 are presented in the paper.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
tablea1.dat 101 120 Stellar sample sorted alphabetically and split
into CRIRES and X-shooter subsections
tablee1.dat 414 85 Table of equivalent width measurements
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Byte-by-byte Description of file: tablea1.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 10 A10 --- Target Target name (1)
12- 15 A4 --- Inst Instrument (2)
17- 31 A15 --- SpType Spectral type from Simbad (3)
32- 38 A7 --- SpType2 Second spectral type from Simbad
40- 45 F6.2 deg GLON ?=- Galactic longitude from Simbad
47- 52 F6.2 deg GLAT ?=- Galactic latitude from Simbad
54- 58 F5.2 mag Bmag ?=- B magnitude from Simbad
60- 64 F5.2 mag Vmag ?=- V magnitude from Simbad
66- 70 F5.2 mag Hmag ?=- H magnitude from Simbad
72- 76 F5.2 mag B-V0F ?=- B-V colour index from
Fitzgerald (1970A&A.....4..234F 1970A&A.....4..234F) (4)
78- 82 F5.2 mag B-V0W ?=- B-V colour index from
Wegner (1994MNRAS.270..229W 1994MNRAS.270..229W) (4)
84- 88 F5.2 mag E(B-V) ?=- Reddening E(B-V) (5)
90- 91 I2 --- r_E(B-V) [1/11]? Reference for E(B-V) (6)
93 I1 --- Nobsa ?=- CRIRES number of observations in
central wavelength 1318.1 nm
95 I1 --- Nobsb ?=- CRIRES number of observations in
central wavelength 1527.9nm
97 I1 --- Nobsc ?=- CRIRES number of observations in
central wavelength 1568.8nm
99 I1 --- Nobsd ?=- CRIRES number of observations in
central wavelength 1574.4nm
101 I1 --- Nobse ?=- CRIRES number of observations in
central wavelength 1624.2nm
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Note (1): Targets are identified by HD number or alternative catalogue
designations for those not in the HD catalogue.
Cepheid names are from Minniti et al. (2020A&A...640A..92M 2020A&A...640A..92M), where B refers to
a Bulge Cepheid and D to a Disc Cepheid.
There are no SIMBAD data for 145501 B nor 160065 B that were detected
using CRIRES.
Note (2): Instruments as follows:
C = CRIRES (no adaptive optics)
CAO = CRIRES using adaptive optics
X = data from Minniti et al. (2020A&A...640A..92M 2020A&A...640A..92M)
XA = archival X-shooter data
XL = the X-shooter low water vapour sample.
All wavelengths were observed in a single setting for X-shooter.
Note (3): CC indicates a classical Cepheid and T2C a type 2 Cepheid; the
intrinsic colours of these stars vary over the pulsation period.
Note (4): Intrinsic (B-V)0 colours for the spectral type are taken from
Fitzgerald (1970A&A.....4..234F 1970A&A.....4..234F) and Wegner (1994MNRAS.270..229W 1994MNRAS.270..229W);
where the values differed, we took an average.
Note (5): Reddening E(B-V) was estimated by comparing the observed (B-V) colours
to the intrinsic colours, except for the entries taken from the literature
shown in n_E(B-V) and towards the Cepheids, as explained in the text.
Note (6): Reference for published reddening values taken from as follows:
1 = Sonnentrucker et al. (2018ApJS..237...40S 2018ApJS..237...40S)
2 = Weselak et al. (2014AcA....64..371W 2014AcA....64..371W)
3 = Crowther et al. (2006MNRAS.372.1407C 2006MNRAS.372.1407C)
4 = Zhekov et al. (2014MNRAS.445.1663Z 2014MNRAS.445.1663Z)
5 = Swihart et al. (2017AJ....153...16S 2017AJ....153...16S, Cat. J/AJ/153/16)
6 = Xiang et al. (2017ApJ...835..107X 2017ApJ...835..107X)
7 = Wegner (2003AN....324..219W 2003AN....324..219W, Cat. J/AN/324/219)
8 = Russeil et al. (2012A&A...538A.142R 2012A&A...538A.142R, Cat. J/A+A/538/A142)
9 = Maiz Apellaniz et al. (2015A&A...583A.132M 2015A&A...583A.132M)
10 = Fan et al. (2017ApJ...850..194F 2017ApJ...850..194F, Cat. J/ApJ/850/194)
11 = Chen et al. (2014A&A...565A.117C 2014A&A...565A.117C, Cat. J/A+A/565/A117)
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Byte-by-byte Description of file: tablee1.dat
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Bytes Format Units Label Explanations
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1- 6 I6 --- HD HD number
8- 11 F4.2 mag E(B-V) ? Reddening E(B-V)
13- 17 F5.2 [cm-2] logNH2 ? log10 of H2 column density
19- 23 F5.2 [cm-2] logNHI ? log10 of HI column density
25- 28 F4.2 --- fH2 ? Fractional H2/HI content
30- 34 F5.1 0.1nm EW-1318 Equivalent width of 1318nm DIB
36- 40 F5.1 0.1nm EW-1527 Equivalent width of 1527nm DIB
42- 46 F5.1 0.1nm EW-1561 Equivalent width of 1561nm DIB
48- 52 F5.1 0.1nm EW-1565 Equivalent width of 1565nm DIB
54- 58 F5.1 0.1nm EW-1567 Equivalent width of 1567nm DIB
60- 65 F6.2 0.1nm EW-NaI-3302p4 ? Equivalent width of NaI(3302Å)
67- 71 F5.2 0.1nm EW-NaI-3303p0 ? Equivalent width of NaI(3303Å)
73- 78 F6.2 0.1nm EW-TiII-3383p8 ? Equivalent width of TiII(3383Å)
80- 84 F5.2 0.1nm EW-FeI-3719p9 ? Equivalent width of FeI(3719Å)
86- 89 F4.2 0.1nm EW-FeI-3859p9 ? Equivalent width of FeI(3859Å)
91- 95 F5.2 0.1nm EW-CNI-3873p9 ? Equivalent width of CN(3873Å)
97-101 F5.2 0.1nm EW-CNI-3874p6 ? Equivalent width of CN(3874Å)
103-106 F4.2 0.1nm EW-CNI-3875p7 ? Equivalent width of CN(3875Å)
108-113 F6.2 0.1nm EW-CaII-3933p6 ? Equivalent width of CaII(3933Å)
115-119 F5.2 0.1nm EW-KI-4044p1 ? Equivalent width of KI(40444Å)
121-126 F6.2 0.1nm EW-C3-4051p6 ? Equivalent width of C3(4051Å)
128-132 F5.2 0.1nm EW-CaI-4226p7 ? Equivalent width of CaI(4226Å)
134-138 F5.2 0.1nm EW-CHp-4232p5 ? Equivalent width of CH+(4232Å)
140-144 F5.2 0.1nm EW-CH-4300p3 ? Equivalent width of CH(4300Å)
146-151 F6.2 0.1nm EW-DIB-4501p8 ? Equivalent width of 4501Å DIB
153-158 F6.2 0.1nm EW-DIB-4726p8 ? Equivalent width of 4726Å DIB
160-165 F6.2 0.1nm EW-DIB-4762p6 ? Equivalent width of 4762Å DIB
167-172 F6.2 0.1nm EW-DIB-4780p0 ? Equivalent width of 4780Å DIB
174-178 F5.2 0.1nm EW-DIB-4984p8 ? Equivalent width of 4984Å DIB
180-184 F5.2 0.1nm EW-DIB-4987p4 ? Equivalent width of 4987Å DIB
186-191 F6.2 0.1nm EW-DIB-5074p5 ? Equivalent width of 5074Å DIB
193-197 F5.2 0.1nm EW-DIB-5236p2 ? Equivalent width of 5236Å DIB
199-203 F5.2 0.1nm EW-DIB-5418p9 ? Equivalent width of 5418Å DIB
205-210 F6.2 0.1nm EW-DIB-5450p6 ? Equivalent width of 5450Å DIB
212-216 F5.2 0.1nm EW-DIB-5494p1 ? Equivalent width of 5494Å DIB
218-223 F6.2 0.1nm EW-DIB-5705p1 ? Equivalent width of 5705Å DIB
225-230 F6.2 0.1nm EW-DIB-5711p6 ? Equivalent width of 5711Å DIB
232-237 F6.2 0.1nm EW-5780 ? Equivalent width of 5780Å DIB
239-244 F6.2 0.1nm EW-5797 ? Equivalent width of 5797Å DIB
246-250 F5.2 0.1nm EW-DIB-5766p1 ? Equivalent width of 5766Å DIB
252-257 F6.2 0.1nm EW-DIB-5849p8 ? Equivalent width of 5449Å DIB
259-265 F7.2 0.1nm EW-NaI-5889p9 ? Equivalent width of NaI(5889Å)
267-272 F6.2 0.1nm EW-NaI-5895p9 ? Equivalent width of NaI(5895Å)
274-278 F5.2 0.1nm EW-DIB-6089p9 ? Equivalent width of 6089Å DIB
280-285 F6.2 0.1nm EW-DIB-6196p0 ? Equivalent width of 6196Å DIB
287-292 F6.2 0.1nm EW-DIB-6203p1 ? Equivalent width of 6203Å DIB
294-298 F5.2 0.1nm EW-DIB-6234p0 ? Equivalent width of 6234Å DIB
300-305 F6.2 0.1nm EW-DIB-6269p9 ? Equivalent width of 6269Å DIB
307-313 F7.2 0.1nm EW-DIB-6283p8 ? Equivalent width of 6283Å DIB
315-319 F5.2 0.1nm EW-DIB-6376p1 ? Equivalent width of 6376Å DIB
321-326 F6.2 0.1nm EW-DIB-6379p3 ? Equivalent width of 6379Å DIB
328-332 F5.2 0.1nm EW-DIB-6397p0 ? Equivalent width of 6397Å DIB
334-338 F5.2 0.1nm EW-DIB-6439p5 ? Equivalent width of 6439Å DIB
340-344 F5.2 0.1nm EW-DIB-6445p3 ? Equivalent width of 6445Å DIB
346-350 F5.2 0.1nm EW-DIB-6449p2 ? Equivalent width of 6449Å DIB
352-356 F5.2 0.1nm EW-DIB-6597p4 ? Equivalent width of 6597Å DIB
358-363 F6.2 0.1nm EW-DIB-6614p0 ? Equivalent width of 6614Å DIB
365-370 F6.2 0.1nm EW-DIB-6993p1 ? Equivalent width of 6993Å DIB
372-377 F6.2 0.1nm EW-DIB-7224p0 ? Equivalent width of 7224Å DIB
379-384 F6.2 0.1nm EW-DIB-7562p2 ? Equivalent width of 7562Å DIB
386-391 F6.2 0.1nm EW-KI-7698P9 ? Equivalent width of KI(7698Å)
393-396 F4.2 0.1nm EW-C2-8757p6 ? Equivalent width of C2(8757Å)
398-401 F4.2 0.1nm EW-C2-8761p2 ? Equivalent width of C2(8761Å)
403-407 F5.2 0.1nm EW-C2-8763p7 ? Equivalent width of C2(8753Å)
409-414 F6.2 0.1nm EW-9632 ? Equivalent width of 9362Å DIB
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Acknowledgements:
Jonathan Smoker, jsmoker(at)eso.org
History:
19-Apr-2023: on-line version
31-Aug-2023: table A1 added (from electronic version of the paper)
(End) Jonathan Smoker [ESO, Chile], Patricia Vannier [CDS] 26-Jan-2023