scholarly journals The Herschel SPIRE Fourier Transform Spectrometer Spectral Feature Finder – III. Line identification and off-axis spectra

2020 ◽  
Vol 496 (4) ◽  
pp. 4906-4922 ◽  
Author(s):  
Chris S Benson ◽  
N Hładczuk ◽  
L D Spencer ◽  
A Robb ◽  
J Scott ◽  
...  
Keyword(s):  
Fourier Transform ◽  
Signal To Noise Ratio ◽  
European Space Agency ◽  
Spectral Feature ◽  
Spectral Lines ◽  
Spectral Features ◽  
Fourier Transform Spectrometer ◽  
Line Identification ◽  
Space Agency ◽  
Feature Fitting

ABSTRACT The European Space Agency Herschel Spectral and Photometric Imaging Receiver (SPIRE) Fourier Transform Spectrometer (FTS) Spectral Feature Finder (FF) project is an automated spectral feature fitting routine developed within the SPIRE instrument team to extract all prominent spectral features from all publicly available SPIRE FTS observations. We present the extension of the FF to include the off-axis detectors of the FTS in sparsely sampled single-pointing observations, the results of which have been ingested into the catalogue. We also present the results from an automated routine for identifications of the atomic/molecular transitions that correspond to the spectral features extracted by the FF. We use a template of 307 atomic fine structure and molecular lines that are commonly found in SPIRE FTS spectra for the cross-match. The routine makes use of information provided by the line identification to search for low signal-to-noise ratio features that have been excluded or missed by the iterative FF. In total, the atomic/molecular transitions of 178 942 lines are identified (corresponding to 83 per cent of the entire FF catalogue), and an additional 33 840 spectral lines associated with missing features from SPIRE FTS observations are added to the FF catalogue.

scholarly journals The Herschel SPIRE Fourier Transform Spectrometer Spectral Feature Finder – V. Rotational measurements of NGC 891

2020 ◽  
Vol 500 (3) ◽  
pp. 3711-3718
Author(s):  
Chris S Benson ◽  
L D Spencer ◽  
I Valtchanov ◽  
J Scott ◽  
N Hładczuk
Keyword(s):  
Fourier Transform ◽  
Spectral Feature ◽  
Far Infrared ◽  
Optical Measurements ◽  
Spectral Features ◽  
Fourier Transform Spectrometer ◽  
Imaging Receiver ◽  
Feature Fitting ◽  
Photometric Imaging ◽  
Infrared Frequencies

ABSTRACT The ESA Herschel Spectral and Photometric Imaging Receiver (SPIRE) Fourier Transform Spectrometer (FTS) Spectral Feature Finder (FF) project is an automated spectral feature fitting routine developed within the SPIRE instrument team to extract all prominent spectral features from all publicly available SPIRE FTS observations. In this work, we demonstrate the use of the FF information extracted from three observations of the edge-on spiral galaxy NGC 891 to measure the rotation of N ii and C i gas at far-infrared frequencies in complement to radio observations of the [H i] 21-cm line and the CO(1-0) transition as well as optical measurements of Hα. We find that measurements of both N ii and C i gas follow a similar velocity profile to that of H i and Hα showing a correlation between neutral and ionized regions of the interstellar medium in the disc of NGC 891.

scholarly journals The Herschel SPIRE Fourier Transform Spectrometer Spectral Feature Finder I. The Spectral Feature Finder and Catalogue

2020 ◽  
Vol 496 (4) ◽  
pp. 4874-4893 ◽  
Author(s):  
R Hopwood ◽  
I Valtchanov ◽  
L D Spencer ◽  
J Scott ◽  
C Benson ◽  
...  
Keyword(s):  
Fourier Transform ◽  
Signal To Noise Ratio ◽  
Spectral Feature ◽  
Fourier Transform Spectrometer ◽  
Line Flux ◽  
Residual Spectrum ◽  
Source Type ◽  
Complex Process ◽  
Wide Range ◽  
Significant Line

ABSTRACT We provide a detailed description of the Herschel/SPIRE Fourier Transform Spectrometer (FTS) Spectral Feature Finder (FF). The FF is an automated process designed to extract significant spectral features from SPIRE FTS data products. Optimizing the number of features found in SPIRE-FTS spectra is challenging. The wide SPIRE-FTS frequency range (447–1568 GHz) leads to many molecular species and atomic fine structure lines falling within the observed bands. As the best spectral resolution of the SPIRE-FTS is ∼1.2 GHz, there can be significant line blending, depending on the source type. In order to find, both efficiently and reliably, features in spectra associated with a wide range of sources, the FF iteratively searches for peaks over a number of signal-to-noise ratio (SNR) thresholds. For each threshold, newly identified features are rigorously checked before being added to the fitting model. At the end of each iteration, the FF simultaneously fits the continuum and features found, with the resulting residual spectrum used in the next iteration. The final FF products report the frequency of the features found and the associated SNRs. Line flux determination is not included as part of the FF products, as extracting reliable line flux from SPIRE-FTS data is a complex process that requires careful evaluation and analysis of the spectra on a case-by-case basis. The FF results are 100 per cent complete for features with SNR greater than 10 and 50–70 per cent complete at SNR of 5. The FF code and all FF products are publicly available via the Herschel Science Archive.

scholarly journals The Herschel SPIRE Fourier Transform Spectrometer Spectral Feature Finder − II. Estimating radial velocity of SPIRE spectral observation sources

2020 ◽  
Vol 496 (4) ◽  
pp. 4894-4905 ◽  
Author(s):  
Jeremy P Scott ◽  
Natalia Hładczuk ◽  
Locke D Spencer ◽  
Ivan Valtchanov ◽  
Chris Benson ◽  
...  
Keyword(s):  
Fourier Transform ◽  
Radial Velocity ◽  
Spectral Feature ◽  
Far Infrared ◽  
Spectral Observation ◽  
Spectral Features ◽  
Fourier Transform Spectrometer ◽  
Infrared Observations ◽  
Characteristic Lines

ABSTRACT The Herschel SPIRE FTS Spectral Feature Finder (FF) detects significant spectral features within SPIRE spectra and employs two routines, and external references, to estimate source radial velocity. The first routine is based on the identification of rotational 12CO emission, the second cross-correlates detected features with a line template containing most of the characteristic lines in typical far infrared observations. In this paper, we outline and validate these routines, summarize the results as they pertain to the FF, and comment on how external references were incorporated.

scholarly journals The Herschel SPIRE Fourier Transform Spectrometer Spectral Feature Finder – IV. Neutral carbon detection in the SPIRE FTS spectra

2020 ◽  
Vol 496 (4) ◽  
pp. 4923-4930 ◽  
Author(s):  
Jeremy P Scott ◽  
Locke D Spencer ◽  
Rosalind Hopwood ◽  
Ivan Valtchanov ◽  
David A Naylor
Keyword(s):  
Fourier Transform ◽  
Feature Detection ◽  
Spectral Feature ◽  
Far Infrared ◽  
Fourier Transform Spectrometer ◽  
Carbon Detection ◽  
Imaging Receiver ◽  
Feature Fitting ◽  
Low Amplitude ◽  
Fine Structure Lines

ABSTRACT The SPIRE Fourier Transform Spectrometer (FTS) Spectral Feature Finder (FF), developed within the Herschel Spectral and Photometric Imaging Receiver (SPIRE) FTS instrument team, is an automated spectral feature fitting routine that attempts to find significant features in SPIRE FTS spectra. The 3P1–3P0 and 3P2–3P1 neutral carbon fine structure lines are common features in carbon-rich far-infrared astrophysical sources. These features can be difficult to detect using an automated feature detection routine due to their typically low amplitude and line blending. In this paper, we describe and validate the FF subroutine designed to detect the neutral carbon emission observed in SPIRE spectral data.

scholarly journals A New Multichannel Fourier Transform Spectrometer

1999 ◽  
Vol 170 ◽  
pp. 36-40
Author(s):  
Tyler E. Nordgren ◽  
Arsen R. Hajian
Keyword(s):  
Fourier Transform ◽  
Extrasolar Planets ◽  
Signal To Noise Ratio ◽  
Fourier Transform Spectrometer ◽  
Test Bed ◽  
Signal To Noise ◽  
Stellar Spectra ◽  
Band Emission ◽  
Noise Ratio ◽  
Ratio Scales

AbstractStellar spectra have been obtained using a multichannel Fourier Transform Spectrometer (FTS) which incorporates components of the Navy Prototype Optical Interferometer. It is well known that a FTS can provide superior wavelength stability as compared to traditional spectrometers. Unfortunately the FTS traditionally suffers from exceptionally poor sensitivity, which until now has limited its uses to sources with high fluxes and/or those with narrow band emission (e.g. the Sun, nebulae, and laboratory samples). We present stellar observations using a new FTS design which overcomes this sensitivity limitation by using a conventional multichannel spectrometer in conjunction with the FTS system. The signal-to-noise ratio of spectra from our test-bed observations are consistent with the theoretical prediction and show that for N channels the sensitivity scales like N, while the signal-to-noise ratio scales like . With this type of an instrument on a 3-m telescope and 9 000 channels we expect to be able to detect and measure such exciting astrophysical phenomenon as gravitational redshifts from single, main sequence stars and extrasolar planets of terrestrial mass.

scholarly journals Analysis of Signal to Noise Ratio in Coronagraph Observations of Coronal Mass Ejections

2020 ◽  
Author(s):  
Johannes Hinrichs ◽  
Jackie A. Davies ◽  
Matthew J. West ◽  
Volker Bothmer ◽  
Bram Bourgoignie ◽  
...  
Keyword(s):  
Coronal Mass Ejections ◽  
Signal To Noise Ratio ◽  
European Space Agency ◽  
Leading Edge ◽  
Outer Edge ◽  
Field Of View ◽  
Signal To Noise ◽  
Space Agency ◽  
Noise Ratio ◽  
Improved Performance

<p>Aims. We analyse the Signal-to-Noise Ratio (SNR) requirements of the European Space Agency (ESA)-funded Solar Coronagraph for OPErations (SCOPE) instrument with respect to the manual and automatic detection of Coronal Mass Ejections (CMEs) in its field of view of 2.5 to 30 solar radii.<br />Methods. For our analysis, SNR values are estimated from observations made by the C3 coronagraph on the Solar and Heliospheric Observatory (SOHO) spacecraft for a number of di erent CMEs. Additionally, we generate a series of artificial coronagraph images, each consisting of a modelled coronal background and a CME, the latter simulated using the Graduated Cylindrical Shell (GCS) model together with the SCRaytrace code available in the Interactive Data Language (IDL) SolarSoft library. Images are created with CME SNR levels between 0.5 and 10 at the outer<br />field of view (FOV) edge, generated by adding Poisson noise, and velocities between 700 km s-1 and 2800 kms-1. The images are analysed for the detectability of the CME above the noise with the automatic CME detection tool CACTus.<br />Results. We find in the analysed C3 images that CMEs near the outer edge of the field of view are typically 2%of the total brightness and have an SNR between 1 and 4 at their leading edge. The automated detection of CMEs in our simulated images by CACTus succeeded well down to SNR = 1 and for CME velocities up to 1400 kms-1. At lower SNR and higher velocity of 2100 kms-1 the detection started to break down. For SCOPE, the results from the two approaches confirm that the initial design goal of SNR = 4 would, if achieved, deliver improved performance over established data used in operations today.</p>

The high-resolution infrared spectrum of BrCl

1994 ◽  
Vol 72 (11-12) ◽  
pp. 1145-1154 ◽  
Author(s):  
Hiromichi Uehara ◽  
Toichi Konno ◽  
Yasushi Ozaki ◽  
Koui Horiai ◽  
Kuniaki Nakagawa ◽  
...  
Keyword(s):  
Fourier Transform ◽  
Standard Deviation ◽  
High Resolution ◽  
Infrared Spectrum ◽  
Potential Function ◽  
Internuclear Distance ◽  
Spectral Lines ◽  
Fourier Transform Spectrometer ◽  
Isotopic Species ◽  
Correction Terms

The high-resolution infrared spectrum of BrCl has been observed with a Fourier transform spectrometer. About 850 spectral lines for the Δν = 1 sequences of the four isotopic species, 79Br35Cl, 81Br35Cl, 79Br37Cl, and 81Br37Cl have been measured between 417 and 461 cm−1. They have been fitted with a standard deviation of 0.000 146 cm−1 to a Dunham potential function using eight coefficients that included two Watson-type Δ correction terms. Dunham Yij coefficients have been derived for each of the four isotopic species. The equilibrium internuclear distance re of BrCl is 2.136 053 28 (67) Å.

The Lyman Far Ultraviolet Spectroscopic Mission (Invited Paper)

1987 ◽  
Vol 7 (2) ◽  
pp. 173-184 ◽  
Author(s):  
Ian R. Tuohy ◽  
Michael A. Dopita
Keyword(s):  
Molecular Hydrogen ◽  
Extreme Ultraviolet ◽  
European Space Agency ◽  
Light Element ◽  
Grazing Incidence ◽  
Spectral Lines ◽  
Important Species ◽  
Element Abundances ◽  
Space Agency ◽  
Far Ultraviolet

AbstractThe Lyman mission will undertake the first sensitive high resolution spectroscopic observations in the largely unexplored 912-1216Å region. This astrophysically critical wavelength interval is exceedingly rich in diagnostic spectral lines such as the Lyman series of atomic hydrogen and deuterium, the Lyman and Werner bands of molecular hydrogen and deuterium, and the resonance lines of numerous important species including CIII, NI-III and OVI. Lyman will have a major impact in all areas of modern astrophysics, with the most fundamental contribution being the determination of light element abundances in the local interstellar medium and in the intergalactic medium at low redshift. The mapping of hot gas (T ∼ 3 × 105K) and molecular hydrogen and HD in the disk and halo of our galaxy represent additional major objectives for which Lyman is uniquely qualified.The Lyman payload will comprise a grazing incidence telescope and three spectroscopic instruments: the prime spectrograph operating between 912-1250Å with a resolution of λ/ Δλ ∼ 30,000, a far ultraviolet spectrograph (1200-2000Å;λ/ Δλ ∼ 10,000), and an extreme ultraviolet spectrograph (100-900Å; λ /Δλ ∼ 300). Observations will be conducted from a highly efficient 48 hour elliptical orbit which will allow long un-interrupted exposures and real time operations. It is anticipated that Lyman will be launched by Ariane in 1996, and will have an operational lifetime of at least 5 years. Data reception and spacecraft control will be undertaken from ground stations in Spain and in Australia.Lyman is currently being studied at Phase-A level by Australia in close coordination with the European Space Agency. The scientific involvement is the responsibility of the Lyman Science Working Group, composed of members representing the various astronomical institutions in Australia. Funding to support the technical and scientific aspects of the mission is provided via the Australian Space Board and the Department of Industry, Technology and Commerce in recognition of the major opportunity that Lyman presents to the Australian aerospace industry.

scholarly journals High-Resolution 3 μm Spectroscopy of Extreme Carbon Stars

1987 ◽  
Vol 120 ◽  
pp. 387-390
Author(s):  
J.-P. Maillard ◽  
S.C. Foster ◽  
T. Amano ◽  
P.A. Feldman
Keyword(s):  
Fourier Transform ◽  
Silicon Nitride ◽  
High Resolution ◽  
Signal To Noise Ratio ◽  
High Signal ◽  
Fourier Transform Spectrometer ◽  
Carbon Stars ◽  
Signal To Noise ◽  
Fundamental Band ◽  
Upper Limits

We have used the Cassegrain-focus Fourier Transform Spectrometer of the Canada-France-Hawaii Telescope to record high-resolution (0.03 cm−1), high signal-to-noise ratio spectra of the extreme carbon stars IRC+10°216 and CIT6 in the 2850–3100 cm−1 region. Upper limits were obtained for the column densities of silicon nitride (2-0 band of the A-X system), ethylene (ν11 fundamental band at ν0 = 2988.7 cm−1), and ethane (ν7 fundamental band at ν0 = 2985.4 cm−1).

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