J/A+A/581/A47 Lines and continuum sky emission in the NIR (Oliva+, 2015)
Lines and continuum sky emission in the near infrared: observational constraints
from deep high spectral resolution spectra with GIANO-TNG.
Oliva E., Origlia L., Scuderi S., Benatti S., Carleo I., Lapenna E.,
Mucciarelli A., Baffa C., Biliotti V., Carbonaro L., Falcini G., Giani E.,
Iuzzolino M., Massi F., Sanna N., Sozzi M., Tozzi A., Ghedina A.,
Ghinassi F., Lodi M., Harutyunyan A., Pedani M.
<Astron. Astrophys. 581, A47 (2015)>
=2015A&A...581A..47O 2015A&A...581A..47O
ADC_Keywords: Spectra, infrared ; Spectroscopy
Keywords: line: identification - instrumentation: spectrograph -
infrared: general - techniques: spectroscopic
Abstract:
Determining the intensity of lines and continuum airglow emission in
the H-band is important for the design of faint-object infrared
spectrographs. Existing spectra at low/medium resolution cannot
disentangle the true sky-continuum from instrumental effects (e.g.
diffuse light in the wings of strong lines).
We aim to obtain, for the first time, a high resolution infrared
spectrum deep enough to set significant constraints on the continuum
emission between the lines in the H-band.
During the second commissioning run of the GIANO high-resolution
spectrograph at the La Palma Observatory, we pointed the instrument
directly to the sky and obtained a deep spectrum that extends from
0.97 to 2.4 micron and includes the whole H-band. The spectrum shows
about 1500 emission lines, a factor of two more than in previous
works. Of these, 80% are identified as OH transitions; half of these
are from highly excited molecules (hot-OH component).
The other lines are attributable to O2 or unidentified. Several of
the faint lines are in spectral regions that were previously believed
to be free of lines emission. The continuum in the H-band is
marginally detected at a level of about 300photons/m2/s/arcsec2/um.
The observed spectrum and the list of observed sky-lines are published
in electronic format. Our measurements indicate that the sky continuum
in the H-band could be even darker than previously believed. However,
the myriad of airglow emission lines severely limits the spectral
ranges where very low background can be effectively achieved with
low/medium resolution spectrographs.
We identify a few spectral bands that could still remain quite dark at
the resolving power foreseen for VLT-MOONS (R∼6,600).
Description:
Tables 1 and 2 list the wavelengths and relative photon fluxes of the
OH airglow lines (Table 1) and the wavelengths and relative photon
fluxes of other airglow lines (Table 2), measured in the Near-Infrared
with the echelle spectrometer GIANO at the Telescopio Nazionale
Galileo. The intensities of the lines (flux) are expressed in units of
photons/m2/s, normalised to the intensity of the brightest line (in
Table1), which is set to 104. The wavelengths are in vacuum and
expressed in Angstrom. The Wavelengths in Table 1 are computed from
the most complete and accurate OH molecular parameters available in
the literature (Bernath & Colin, 2009, J. Mol. Spec., 257, 20). Table
4 contains the observed spectrum in the Y,J and H photometric bands.
The wavelengths are in vaccuum and in Angstrom. The spectral flux is
expressed in units of photons/m2/s/Angstrom, please note that the
flux calibration is uncertain (see the paper for details).
File Summary:
--------------------------------------------------------------------------------
FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
table1.dat 55 603 OH airglow line wavelengths and relative fluxes
table2.dat 30 293 *Non-OH line wavelengths and relative fluxes
table4.dat 18 49864 Airglow spectrum covering the Y, J, H-bands
--------------------------------------------------------------------------------
Note on table2.dat: Identification based on the HITRAN database.
--------------------------------------------------------------------------------
Byte-by-byte Description of file: table1.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 9 F9.3 0.1nm lambda1 [9792/22984] Vacuum wavelength of the first
line of the doublet (Å)
11- 24 A14 --- Iden1 Line identification (1)
26- 34 F9.3 0.1nm lambda2 [9791/22988] Vacuum wavelength of the second
line of the doublet (Å)
36- 49 A14 --- Iden2 Line identification (1)
51- 55 I5 --- Flux [3/10000] Relative line photon flux of doublet
--------------------------------------------------------------------------------
Note (1): Lines are grouped in pairs, one for each lambda-doublet.
--------------------------------------------------------------------------------
Byte-by-byte Description of file: table2.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 8 F8.2 0.1nm lambda [10489/21794] Vacuum wavelength (Å)
11- 22 A12 --- Iden Line identification
26- 28 I3 --- Flux [4/820] Relative line photon flux
30 A1 --- Flag [a-l] Notes to individual lines (1)
--------------------------------------------------------------------------------
Note (1): Notes as follows:
a = broad
b = scales like O2 lines
c = blend with OH [7-4]P1(7.5)
d = blend
e = blend with OH [8-5]R1(3.5)
f = blend with [8-5]R1(2.5)
g = blend with [8-5]R1(1.5)
h = possible doublet
i = broad, asymmetric
j = blend with OH [4,2]P2(9.5)
k = blend with OH [4-2]Q1f(3.5)
l = blend with OH [6,4]R1(16.5))
--------------------------------------------------------------------------------
Byte-by-byte Description of file: table4.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 9 F9.3 0.1nm lambda [9790/18022] Vacuum wavelength (Å)
11- 18 F8.4 10/m2/s/nm Flux [-1/421] Spectral flux (photons/m2/s/Å)
--------------------------------------------------------------------------------
Acknowledgements:
Ernesto Oliva, oliva(at)arcetri.astro.it,
Fabrizio Massi, fmassi(at)arcetri.astro.it
(End) Ernesto Oliva [INAF - Arcetri], Patricia Vannier [CDS] 09-Jul-2015