The infrared spectrograph (irs) on the spitzer space telescope

TLDR: The Infrared Spectrograph (IRS) as discussed by the authors is one of the three science instruments on the Spitzer Space Telescope and is optimized to take full advantage of the very low background in the space environment.

Abstract: The Infrared Spectrograph (IRS) is one of three science instruments on the Spitzer Space Telescope .T he IRS comprises four separate spectrograph modules covering the wavelength range from 5.3 to 38 � m with spectral resolutions, R ¼ k=� k � 90 and 600, and it was optimized to take full advantage of the very low background in the space environment. The IRS is performing at or better than the prelaunch predictions. An autonomous target acquisition capability enables the IRS to locate the mid-infrared centroid of a source, providing the information so that the spacecraft can accurately offset that centroid to a selected slit. This feature is particularly useful when taking spectra of sources with poorly known coordinates. An automated data-reduction pipeline has been developed at the Spitzer Science Center. Subject headingg infrared: general — instrumentation: spectrographs — space vehicles: instruments

Figures

TABLE 1 Properties of the IRS

Fig. 2.—SH spectrum of the Be star Cas. The lower panel shows a continuum-corrected spectrum with the identifications of the hydrogen recombination lines used to check the wavelength calibration of this module. The crosses mark the location of unusable wavelength elements.

Fig. 4.—Low-resolution spectrum of UGC 5101 (using both SL and LL), showing several strong bands from PAHs, dust, and ice along with atomic emission lines (redshifted for z ¼ 0:039). The integration time was 12 s in each SL subslit and 28 s in each LL subslit (total 80 s). Armus et al. (2004) discuss this spectrum more completely.

Fig. 3.—High-resolution spectrum of the starburst galaxy NGC 7714 (using both SH and LH) with the detected features marked (shifted for z ¼ 0:0093). This spectrum was obtained with 240 s of integration in SH and LH (each). Brandl et al. (2004) describe these observations in more detail.

Fig. 1.—Infrared Spectrograph on Spitzer. The four IRS modules, SH, SL (which includes the peak-up cameras), LH, and LL are marked. A schematic of the location of the spectrograph slits on the Spitzer focal plane is presented in Fig. 2 of Werner et al. (2004).

Frequently asked questions

Q1. What are the contributions mentioned in the paper "The infrared spectrograph (irs) on the spitzer space telescope" ?

The IRS this paper is one of the three science instruments on the Spitzer Space Telescope, and it was designed to take full advantage of the very low background in the space environment. 

Q2. What are the future works mentioned in the paper "The infrared spectrograph (irs) on the spitzer space telescope" ?

The IRS also allows mid-infrared spectroscopy of objects such as brown dwarfs, individual stars in neighboring galaxies, and a wide variety of other sources previously difficult or impossible to study spectroscopically in the midinfrared. This description of the IRS gives the potential observer a brief review of its design, its capabilities, and how to use it. 

Q3. What is the maximum flux density for a peak-up source?

The allowed ranges of flux densities for blue and red peak-up point sources are fblue ¼ 0:8 150 mJy and fred ¼ 1:4 340 mJy, respectively. 

Q4. What are the four categories of data that are supplied in FITS files to the observer?

The IRS array data supplied in FITS files to the observer are organized into four categories: Engineering Pipeline Data, Basic Calibrated Data (BCD), Browse-Quality Data (BQD), and Calibration Data. 

Q5. How many detector reads will be produced?

The Engineering Data pipeline will process the data, which will have the form of six data cubes (three integration cycles at each of the two nod positions alongthe slit), each 128 ; 128 pixels ; 16 detector reads in size. 

Q6. Why is the IRS more sensitive to damage than the other science instruments on board Spitzer?

The IRS is more sensitive to damage than the other science instruments on board Spitzer because it is operating at lower background conditions where even a small increase in dark current has a significant effect. 

Q7. How many mJy fluxes are allowed for the blue and red?

to avoid excessive integration times and a higher probability of failure, the authors recommend a flux of at least 2 mJy for the blue and 5 mJy for the red. 

Q8. What is the way to obtain midinfrared images?

an interim method called CHEAP (Cornell High-Efficiency Advanced Peak-up) has been used extensively to obtain midinfrared images. 

Q9. What is the critical step of the in-orbit checkout phase?

Mapping the relative positions of each field of view and the spacecraft’s Pointing Calibration Reference Sensor (PCRS) was the most critical step of the in-orbit checkout (IOC) phase. 

Q10. How did the overlaps help the internal cross-calibration of the IRS?

These overlaps were also used to search for leaks in the order-sorting filters by observing ‘‘cold’’ and ‘‘hot’’ sources in two overlapping orders. 

Q11. How can the IRS accurately offset to the selected slits?

As long as the coordinates of a target are accurate enough to place it on the peak-up imaging field and it is the brightest object in the field, the IRS will accurately offset to the selected slits. 

Q12. What is the way to capture data from the IRS?

When the IRS is operating, all four of its detector arrays are clocked simultaneously, but it is only possible to capture data from one array at a time. 

Q13. What is the way to peak up a source?

In the event that the science target cannot also serve as the peak-up target (e.g., if its flux is too low or too high), the ‘‘offset peak-up’’ mode gives the option of peaking-up using a nearby source. 

Q14. What are the additional BCD data files?

Additional BCD data files include uncertainty images that accompany each slope image and various intermediate images that do not have all of the pipeline processing corrections applied. 

Q15. Why was the design of the IRS driven by the objective of maximizing sensitivity?

The design of the IRS was driven by the objective of maximizing sensitivity given the 85 cm aperture of the Spitzer Space Telescope (Werner et al. 2004) and the then-available detectors.