J/A+A/683/A199 DIBs in Gaia DR3 RVS spectra (Zhao+, 2024)
Diffuse interstellar bands in Gaia DR3 RVS spectra.
New measurements based on machine learning.
Zhao H., Schultheis M., Qu C., Zwitter T.
<Astron. Astrophys. 683, A199 (2024)>
=2024A&A...683A.199Z 2024A&A...683A.199Z (SIMBAD/NED BibCode)
ADC_Keywords: Interstellar medium ; Equivalent widths
Keywords: ISM: lines and bands
Abstract:
Diffuse interstellar bands (DIBs) are weak and broad interstellar
absorption features in astronomical spectra that originate from
unknown molecules. To measure DIBs in spectra of late-type stars more
accurately and more efficiently, we developed a random forest model to
isolate the DIB features from the stellar components. We applied this
method to 780 thousand spectra collected by the Gaia Radial Velocity
Spectrometer (RVS) that were published in the third data release
(DR3). After subtracting the stellar components, we modeled the DIB at
8621Å (λ8621) with a Gaussian function and the DIB around
8648Å (λ8648) with a Lorentzian function. After quality
control, we selected 7619 reliable measurements for DIB λ8621.
The equivalent width (EW) of DIB λ8621 presented a moderate
linear correlation with dust reddening, which was consistent with our
previous measurements in Gaia DR3 and the newly focused product
release. The rest-frame wavelength of DIB λ8621 was updated as
λ0=8623.141±0.030Å in vacuum, corresponding to
8620.766Å in air, which was determined by 77 DIB measurements
toward the Galactic anticenter. The mean uncertainty of the fit
central wave-length of these 77 measurements is 0.256Å. With the
peak-finding method and a coarse analysis, DIB λ8621 was found
to correlate better with the neutral hydrogen than with the molecular
hydrogen (represented by 12CO J=(1-0) emission). We also obtained
179 reliable measurements of DIB λ8648 in the RVS spectra of
individual stars for the first time, further confirming this very
broad DIB feature. Its EW and central wavelength presented a linear
relation with those of DIB λ8621. A rough estimation of
λ0 for DIB λ8648 was 8646.31Å in vacuum,
corresponding to 8643.93Å in air, assuming that the carriers of
λ8621 and λ8648 are comoving. Finally, we confirmed the
impact of stellar residuals on the DIB measurements in Gaia DR3, which
led to a distortion of the DIB profile and a shift of the center
(≲0.5Å), but the EW was consistent with our new measurements. With
our measurements and analyses, we propose that the approach based on
machine learning can be widely applied to measure DIBs in numerous
spectra from spectroscopic surveys.
Description:
We developed a Random Forest model to isolate the DIB features from
the stellar components and applied this method to 780 thousand spectra
collected by the Gaia Radial Velocity Spectrometer (RVS) that were
published in the third data release (DR3). After subtracting the
stellar components, we modeled the DIB at 862.1nm with a Gaussian
function and the DIB around 864.8nm with a Lorentzian function. After
quality control, we selected 7619 reliable DIB measurements. Their
fitted DIB parameters, as well as the parameters related to the
background stars and spectra, are released in this file.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table.dat 284 7619 Fit results and measurements of the two DIBs
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See also:
I/361 : Gaia Focused Product Release (Gaia FPR) (Gaia Collaboration, 2023)
Byte-by-byte Description of file: table.dat
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Bytes Format Units Label Explanations
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1- 19 I19 --- GaiaDR3 Gaia DR3 source ID
21- 27 F7.3 deg GLON Galactic longitude (J2016)
29- 35 F7.3 deg GLAT Galactic latitude (J2016)
37- 41 F5.2 kpc rmedgeo Calibrated distance from Bailer-Jones et al.,
2021, Cat. I/352
43- 48 F6.2 --- ismsnr S/N of ISM spectra
50- 54 F5.3 --- chi2dof Chi-square over dof
56- 61 F6.4 --- CD8621 Central Depth (CD) of DIB8621
63- 68 F6.4 --- e_CD8621 Lower limit of CD8621
70- 75 F6.4 --- E_CD8621 Upper limit of CD8621
77- 83 F7.2 0.1nm CW8621 Central Wavelength (CW) of DIB8621
85- 91 F7.2 0.1nm e_CW8621 Lower limit of CW8621
93- 99 F7.2 0.1nm E_CW8621 Upper limit of CW8621
101-104 F4.2 0.1nm W8621 Gaussian width of DIB8621
106-109 F4.2 0.1nm e_W8621 Lower limit of w8621
111-114 F4.2 0.1nm E_W8621 Upper limit of w8621
116-121 F6.4 --- CD8648 Central Depth (CD) of DIB8621
123-128 F6.4 --- e_CD8648 Lower limit of CD8648
130-135 F6.4 --- E_CD8648 Upper limit of CD8648
137-143 F7.2 0.1nm CW8648 Central Wavelength (CW) of DIB8648
145-151 F7.2 0.1nm e_CW8648 Lower limit of CW8648
153-159 F7.2 0.1nm E_CW8648 Upper limit of CW8648
161-165 F5.2 0.1nm W8648 Lorentzian width of DIB8648
167-171 F5.2 0.1nm e_W8648 Lower limit of w8648
173-177 F5.2 0.1nm E_W8648 Upper limit of w8648
179-185 F7.4 --- a1 Continuum=a1*wave+a2
187-193 F7.4 --- e_a1 [] Lower limit of a1
195-201 F7.4 --- E_a1 [] Upper limit of a1
203-208 F6.2 --- a2 Continuum=a1*wave+a2
210-215 F6.2 --- e_a2 [] Lower limit of a2
217-222 F6.2 --- E_a2 [] Upper limit of a2
224-228 F5.3 0.1nm EW8621 Equivalent width of DIB8621
230-234 F5.3 0.1nm E_EW8621 Upper limit of EW8621
236-240 F5.3 0.1nm e_EW8621 Lower limit of EW8621
242-246 F5.3 0.1nm EW8648 Equivalent width of DIB8648
248-252 F5.3 0.1nm E_EW8648 Upper limit of EW8648
254-258 F5.3 0.1nm e_EW8648 Lower limit of EW8648
260-264 F5.3 0.1nm EW8621int Integrated EW8621
266-270 F5.3 0.1nm EW8648int Integrated EW8648
272-277 F6.4 --- Rc8621 Noise level near DIB8621
279-284 F6.4 --- Rc8648 Noise level near DIB8621
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Acknowledgements:
He Zhao, he.zhao(at)oca.eu
(End) Patricia Vannier [CDS] 18-Dec-2023