J/A+A/666/L12 Stacked Gaia-RVS spectra broad DIB around 864.8nm (Zhao+, 2022)
Solid confirmation of the broad DIB around 864.8 nm using stacked
Gaia-RVS spectra.
Zhao H., Schultheis M., Zwitter T., Bailer-Jones C.A.L., Panuzzo P.,
Sartoretti P., Seabroke G.M., Recio-Blanco A., de Laverny P.,
Kordopatis G., Creevey O.L., Dharmawardena T.E., Fremat Y.,
Sordo R., Drimmel R., Marshall D.J., Palicio P.A., Contursi G.,
Alvarez M.A., Baker S., Benson K., Dolding C., Huckle H.E.,
Smith M., Marchal O., Ordenovic C., Pailler F., Slezak I.
<Astron. Astrophys. 666, L12 (2022)>
=2022A&A...666L..12Z 2022A&A...666L..12Z (SIMBAD/NED BibCode)
ADC_Keywords: Interstellar medium ; Spectra, optical ; Equivalent widths
Keywords: ISM: lines and bands
Abstract:
Studies of the correlation between different diffuse interstellar
bands (DIBs) are important for exploring their origins. However, the
Gaia-RVS spectral window between 846 and 870nm contains few DIBs,
the strong DIB at 862nm being the only convincingly confirmed one.
Here we attempt to confirm the existence of a broad DIB around 864.8nm
and estimate its characteristics using the stacked Gaia-RVS spectra of
a large number of stars. We study the correlations between the two
DIBs at 862nm (λ862) and 864.8nm (λ864.8), as well as
the interstellar extinction.
We obtained spectra of the interstellar medium (ISM) absorption by
subtracting the stellar components using templates constructed from
real spectra at high Galactic latitudes with low extinctions. We then
stacked the ISM spectra in Galactic coordinates (l, b) - pixelized by
the HEALPix scheme - to measure the DIBs. The stacked spectrum is
modeled by the profiles of the two DIBs, Gaussian for λ862 and
Lorentzian for λ864.8, and a linear continuum. We report the
fitted central depth (CD), central wavelength, equivalent width (EW),
and their uncertainties for the two DIBs.
We obtain 8458 stacked spectra in total, of which 1103 (13%) have
reliable fitting results after applying numerous conservative filters.
This work is the first of its kind to fit and measure λ862 and
λ864.8 simultaneously in cool-star spectra. Based on these
measurements, we find that the EWs and CDs of λ862 and
λ864.8 are well correlated with each other, with Pearson
coefficients (rp) of 0.78 and 0.87, respectively. The full width at
half maximum (FWHM) of λ864.8 is estimated as 1.62±0.33nm
which compares to 0.55±0.06nm for λ862. We also measure
the vacuum rest-frame wavelength of λ864.8 to be
λ0=864.53±0.14nm, smaller than previous estimates.
We find solid confirmation of the existence of the DIB around 864.8nm
based on an exploration of its correlation with λ862 and
estimation of its FWHM. The DIB λ864.8 is very broad and
shallow. That at λ862 correlates better with E(BP-RP)
than λ864.8. The profiles of the two DIBs could strongly
overlap with each other, which contributes to the skew of the
λ862 profile.
Description:
Based on the measurements in 1103 stacked Gaia-RVS spectra, we make a
solid confirmation of the DIB around 864.8nm by its good intensity
correlation with the DIB at 862nm and its clear and broad profile in
the ISM spectra. DIB864.8 is a very broad and shallow DIB. Its profile
is better modeled by a Lorentzian function than Gaussian. The profiles
of the two DIBs could be strongly overlapped with each other, which
contributes to the skew of the DIB862 profile.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table.dat 93 1103 Fit results and measurements of the two DIBs
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See also:
I/355 : Gaia DR3 Part 1. Main source (Gaia Collaboration, 2022)
Byte-by-byte Description of file: table.dat
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Bytes Format Units Label Explanations
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1- 5 I5 --- Npixel HEALPix pixel
7- 9 I3 --- Ntar Target number
11- 16 F6.1 --- S/N S/N of stacked spectra
18- 23 F6.4 --- CD1 Central depth of DIB862
25- 31 F7.2 0.1nm Cwave1 Central wavelength of DIB862
33- 36 F4.2 0.1nm FWHM1 FWHM of DIB862
38- 43 F6.4 --- CD2 Central depth of DIB864.8
45- 51 F7.2 0.1nm Cwave2 Central wavelength of DIB864.8
53- 57 F5.2 0.1nm FWHM2 FWHM of DIB864.8
59- 63 F5.3 0.1nm EW1 Equivalent width of DIB862
65- 69 F5.3 0.1nm e_EW1 EW error of DIB862
71- 75 F5.3 0.1nm EW2 Equivalent width of DIB864.8
77- 81 F5.3 0.1nm e_EW2 EW error of DIB864.8
83- 87 F5.3 mag E(BP-RP) Color excess
89- 93 F5.3 mag e_E(BP-RP) Color excess uncertainty
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Acknowledgements:
He Zhao, he.zhao(at)oca.eu
(End) Patricia Vannier [CDS] 03-Oct-2022