The SAFARI imaging spectrometer for the SPICA space observatory

Roelfsema, Peter; Giard, M.; Najarro, F.; Wafelbakker, Kees; Jellema, Willem; Jackson, B. D.; Swinyard, Bruce; Audard, M.; Doi, Yasuo; Griffin, Matthew Joseph; Helmich, Frank; Kerschbaum, F.; Meyer, Michael; Naylor, David; Nielsen, H. Schnedler; Olofsson, G.; Poglitsch, A.; Spinoglio, L.; Vandenbussche, B.; Isaak, K. G.; Goicoechea, J. R.

doi:10.1117/12.927010

Cited by 34 publications

(21 citation statements)

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“…It will be possible to measure pure H 2 rotational lines at high redshifts of z≈6-7, almost reaching the reionization era of the universe, with the SPace Infrared telescope for Cosmology and Astrophysics (SPICA) and the Cryogenic Aperture Large Infrared Submillimeter Telescope Observatory (CALISTO), planned for the 2020 decade (Roelfsema et al 2012;Bradford et al 2015).…”

Section: Future Prospectsmentioning

confidence: 99%

LIGHTING THE DARK MOLECULAR GAS: H₂ AS A DIRECT TRACER

Togi

Smith

2016

ApJ

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Robust knowledge of molecular gas mass is critical for understanding star formation in galaxies. The H 2 molecule does not emit efficiently in the cold interstellar medium, hence the molecular gas content of galaxies is typically inferred using indirect tracers. At low metallicity and in other extreme environments, these tracers can be subject to substantial biases. We present a new method of estimating total molecular gas mass in galaxies directly from pure mid-infrared rotational H 2 emission. By assuming a power-law distribution of H 2 rotational temperatures, we can accurately model H 2 excitation and reliably obtain warm (T100 K) H 2 gas masses by varying only the power law's slope. With sensitivities typical of Spitzer/IRS, we are able to directly probe the H 2 content via rotational emission down to ∼80 K, accounting for ∼15% of the total molecular gas mass in a galaxy. By extrapolating the fitted power-law temperature distributions to a calibrated single lower cutoff temperature, the model also recovers the total molecular content within a factor of ∼2.2 in a diverse sample of galaxies, and a subset of broken powerlaw models performs similarly well. In ULIRGs, the fraction of warm H 2 gas rises with dust temperature, with some dependency on α CO . In a sample of five low-metallicity galaxies ranging down to [ ] + = 12 log O H 7.8, the model yields molecular masses up to ∼100×larger than implied by CO, in good agreement with other methods based on dust mass and star formation depletion timescale. This technique offers real promise for assessing molecular content in the early universe where CO and dust-based methods may fail.

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Section: Future Prospectsmentioning

confidence: 99%

LIGHTING THE DARK MOLECULAR GAS: H₂ AS A DIRECT TRACER

Togi

Smith

2016

ApJ

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“…To exploit the sensitivity of state-of-the-art detectors on these missions stray light must be controlled using feedhorn coupled detectors. The SAFARI instrument (Roelfsema et al 2012) under development for the SPICA mission is an imaging FTS employing feedhorns and will encounter a similar frequency dependent beam profile and require a similar analysis for semi-extended sources as that described in this paper.…”

Section: Resultsmentioning

confidence: 99%

Observing extended sources with theHerschelSPIRE Fourier Transform Spectrometer

Polehampton

Etxaluze

et al. 2013

A&A

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The Spectral and Photometric Imaging Receiver (SPIRE) on the European Space Agency's Herschel Space Observatory utilizes a pioneering design for its imaging spectrometer in the form of a Fourier Transform Spectrometer (FTS). The standard FTS data reduction and calibration schemes are aimed at objects with either a spatial extent that is much larger than the beam size or a source that can be approximated as a point source within the beam. However, when sources are of intermediate spatial extent, neither of these calibrations schemes is appropriate and both the spatial response of the instrument and the source's light profile must be taken into account and the coupling between them explicitly derived. To that end, we derive the necessary corrections using an observed spectrum of a fully extended source with the beam profile and considering the source's light profile. We apply the derived correction to several observations of planets and compare the corrected spectra with their spectral models to study the beam coupling efficiency of the instrument in the case of partially extended sources. We find that we can apply these correction factors for sources with angular sizes up to θ D ∼ 17 . We demonstrate how the angular size of an extended source can be estimated using the difference between the subspectra observed at the overlap bandwidth of the two frequency channels in the spectrometer, at 959 < ν < 989 GHz. Using this technique on an observation of Saturn, we estimate a size of 17.2 , which is 3% larger than its true size on the day of observation. Finally, we show the results of the correction applied on observations of a nearby galaxy, M82, and the compact core of a Galactic molecular cloud, Sgr B2.

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“…The combination of very sensitive large-format filled TES arrays fully sampling a large instantaneous FoV and its high spectral resolving power, makes Safari an extremely powerful unbiased spectroscopic imaging instrument characterizing for example the spatial and spectral energy distribution of very faint point sources just above the natural background. An overview of the key scientific themes to be addressed by Safari and the instrument design is given in [2][3].…”

Section: Introductionmentioning

confidence: 99%

The optical design concept of SPICA-SAFARI

Jellema

Kruizinga²,

Visser³

et al. 2012

Space Telescopes and Instrumentation 2012: Optical, Infrared, and Millimeter Wave

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The Safari instrument on the Japanese SPICA mission is a zodiacal background limited imaging spectrometer offering a photometric imaging (R ≈ 2), and a low (R = 100) and medium spectral resolution (R = 2000 at 100 μm) spectroscopy mode in three photometric bands covering the 34-210 μm wavelength range. The instrument utilizes Nyquist sampled filled arrays of very sensitive TES detectors providing a 2'x2' instantaneous field of view. The all-reflective optical system of Safari is highly modular and consists of an input optics module containing the entrance shutter, a calibration source and a pair of filter wheels, followed by an interferometer and finally the camera bay optics accommodating the focal-plane arrays. The optical design is largely driven and constrained by volume inviting for a compact threedimensional arrangement of the interferometer and camera bay optics without compromising the optical performance requirements associated with a diffraction-and background-limited spectroscopic imaging instrument. Central to the optics we present a flexible and compact non-polarizing Mach-Zehnder interferometer layout, with dual input and output ports, employing a novel FTS scan mechanism based on magnetic bearings and a linear motor. In this paper we discuss the conceptual design of the focal-plane optics and describe how we implement the optical instrument functions, define the photometric bands, deal with straylight control, diffraction and thermal emission in the long-wavelength limit and interface to the large-format FPA arrays at one end and the SPICA telescope assembly at the other end.

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The SAFARI imaging spectrometer for the SPICA space observatory

Cited by 34 publications

References 0 publications

LIGHTING THE DARK MOLECULAR GAS: H₂ AS A DIRECT TRACER

LIGHTING THE DARK MOLECULAR GAS: H₂ AS A DIRECT TRACER

Observing extended sources with theHerschelSPIRE Fourier Transform Spectrometer

The optical design concept of SPICA-SAFARI

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The SAFARI imaging spectrometer for the SPICA space observatory

Cited by 34 publications

References 0 publications

LIGHTING THE DARK MOLECULAR GAS: H2 AS A DIRECT TRACER

LIGHTING THE DARK MOLECULAR GAS: H2 AS A DIRECT TRACER

Observing extended sources with theHerschelSPIRE Fourier Transform Spectrometer

The optical design concept of SPICA-SAFARI

Contact Info

Product

Resources

About

LIGHTING THE DARK MOLECULAR GAS: H₂ AS A DIRECT TRACER

LIGHTING THE DARK MOLECULAR GAS: H₂ AS A DIRECT TRACER