Integral Field Spectroscopy

1. Universidad de Almeria Viernes de Ciencia 14 January 2011 Integral Field Spectroscopy S.F.Sánchez (CAHA)

2. IFS or 3D Spectroscopy • Is the spectroscopic technique that samples a quasi-continous area in the sky (FOV). • The FOV is sampled by small aperture elements named spaxels, which correspond to pixels of an image. • Light coming through each spaxel is transported to the entrance of an spectrograph. • The image/plane and focal/plane are completely decoupled: Lot of software is required to reconstruct the orginal spatial shape at each wavelength.

3. Different kind of spaxels. • Is the spectroscopic technique that samples a quasi-continous area in the sky (FOV). • The FOV is sampled by small aperture elements named spaxels, which correspond to pixels of an image. • Light coming through each spaxel is transported to the entrance of an spectrograph. • The image/plane and focal/plane are completely decoupled: Lot of software is required to reconstruct the orginal spatial shape at each wavelength.

4. How to send the light to the Spectrograph? • Image Slicers: Light is “sliced” in small continous pseudo-slits: SINFONI, MUSE... • Lensarrays: Continous lensarray is focused in separated apertures: SAURON, TIGER... • Fiber-Bundles (+lensarrays): Lights is conducted by fibers: PMAS/PPAK, VIMOS, GMOS...

5. Fiber Feed IFS technique

6. The Raw data of FF IFUs

7. The Raw data of FF IFUs

8. FF IFU: Data Reduction (I) • Continuum exposure used to find and trace the location of the spectra in the CCD. • The FWHM of the spectra projected in the cross-dispersion axis determined. • Gaussian extraction performed. • Comparison Arc used to determine the distorsion correction and wavelength solution, latter applied to the data.

9. FF IFU: Data Reduction (II) • Sky-frames taken during the twilight used to correct for the differentical transmission fiber to fiber (wavelength dependent). • Spectrophotometric calibration standard star exposure used to determine the flux calibration, applied to the science frames. • Science (331), Sky (36) and calibration spectra (15) are separated in different frames, once reduced. • Sky spectrum is derived for each frae (median+3sigma clipping of the 36 sky-spectra) and the subtracted to the data.

10. FF IFU: Data Reduction (III) • Re-arrange the dithered pointings in a single row-stacked spectra frame, plus the complementary Position Table. • Mask the spectral pixel strongly affected by the vignetting. • Interpolate the final Mosaic into a common grid datacube of 1”/pixel. • When available, perform a flux recalibration based on broad-band photometry.

11. The Raw data of FF IFUs

12. Tracing process (I)

13. Tracing process (II)

14. Extraction: How to Add flux?

15. Extraction: cross-talk?

16. Extraction: The final product

17. Distorsions: Shifting lines.

18. Dispersion:Which line are you?

19. Fiber-to-Fiber transmission

20. Sky subtraction... If possible.

21. Where my spectra comes from?.

22. PMAS/PPAK: Dithering. • 3 position dither pattern per pointing. • Complete spatial covering of the FOV. • Increase of the spatial resolution. • Fully implemented in R3D.

23. WF-IFS Mosaics Experiment

24. Matching the pointings. • The pointings overlap, in at least 11 spectra. • The change in transparency is critical • Accuracy of the telescope offsets is also critical.

25. Results: Orion (Sánchez et al. 2006)

26. Results: M74 (Sánchez et al. 2010)

27. CALIFA: Introduction • Survey of ~600 Galaxies in the Local Universe, using Integral Field Spectroscopy, with PPAK mounted at the 3.5m Telescope. • Proposed by 53 researchers from 8 countries: • PI:S.F.Sánchez. • Board: R. Kennicutt (Chair), A. Gil de Paz (co-PI), J.M. Vilchez, L. Wisotzki, G. Van den Ven. • 210 dark nights allocated in next 3 years. • Started on July 1st 2010.

28. CALIFA: Science Goals • Model the resolved stellar population in galaxies of any kind and trace the star formation history. • Determine the nature of the ionized gas and its chemical abundance gradients. • Determine the 2D kinematic structure of galaxies in the local Universe.

29. Results (I): Mother Sample • Characterization of the Sample: • How are the galaxies we are going to observe? Morphology, Spectral Type, Nuclear or Starformation activity… • Do we have any possible Bias and how we can control/correct them?

30. Results (II): Reduced Data • Pilot Studies: 43 objects observed in 2009: • A) V300 (R~450); 1.5h Int.; • 3700-7100 A. • B) V600 (R~950); 1.5h Int.; • 3800-6700 A. • CALIFA First Runs (June-July 2009): 21 objects: • A) V500 (R~890); 45m int: • 3700-7100 A. • B) V1200 (R~1850); 1.5h int: • 3500-4100A. • R at 5000 A

31. Results (III): Science • Diversity of the observed galaxies: Different colors, magnitudes, morphologies, gas content… a photograph of the Local Universe! • Resolved properties of the stellar populations. • Stellar Kinematics. • Properties of the Ionized gas. • All included in the First Article (in prep.)

32. 3D Spectroscopy Summary • IFS is a common user technique (40% of the observations done with the 3.5m at CAHA, 80% of one of the UT/VLT). • Many of proposed or new generations instruments are IFUs (MUSE, MEGARA). • JWST will include an IFU. • There is science that can only be done with IFUs. • Any future astronomer should be prepared to use it.