Presentation is loading. Please wait.

Presentation is loading. Please wait.

New Atomic Data for Astrophysics by High Resolution Fourier Transform Spectrometry l Some technical developments and future challenges M. P. Ruffoni, J.

Similar presentations


Presentation on theme: "New Atomic Data for Astrophysics by High Resolution Fourier Transform Spectrometry l Some technical developments and future challenges M. P. Ruffoni, J."— Presentation transcript:

1 New Atomic Data for Astrophysics by High Resolution Fourier Transform Spectrometry l Some technical developments and future challenges M. P. Ruffoni, J. C. Pickering, A. P. Thorne, C. Holmes, R. Blackwell-Whitehead M. P. Ruffoni - 14th July 2011 - OSA FTS Conference, Toronto

2 1)Calibrating VUV FTS spectra from hollow cathode lamps (HCLs) Existing standards – Ar II lines from Learner & Thorne (1988). Improved standards – wavelengths from laser frequency combs. Example: High-precision wavelengths for -variation studies. 2)Challenges in measuring IR log(gf)s and branching fractions Such numbers are in high demand by astronomers. Intensity of all transitions from an upper level must be known. However, large gaps between lines hinder intensity calibration. Example: log(gf) values needed for the APOGEE project. Outline M. P. Ruffoni - 14th July 2011 - OSA FTS Conference, Toronto

3 Hollow-cathode Light Source (HCL) To vacuum pump High voltage ~600 V at 50-1000 mA Water cooled Ne and/or Ar gas at 1-3 mbar Glass AnodeCathodeAnode Designed and manufactured at Imperial College based on a similar lamp in use at Lund Observatory, Sweden. M. P. Ruffoni - 14th July 2011 - OSA FTS Conference, Toronto

4 Calibration Standards AuthorStudyingAccuracy Pickering et al. (2000) Cr II, Zn II, and Ni II 0.002cm -1 at 2000Å 0.004cm -1 at 1700Å Aldenius et al. (2006) Zn II 0.001 to 0.002cm -1 at 2500Å Ar II standard linesMg I and II standard lines Wavenumbers calibrated through a simple linear correction. Ar II standards recommended by Learner & Thorne (1988) are typically used. However Recommended lines are in the visible. Overlapping spectra needed to carry calibration to the UV and VUV. Gas line  can sometimes change with lamp running conditions. [a] Salumbides et al., MNRAS 373 pp. L41 (2006) [b] Batteiger et al., Phys Rev A 80 pp. 022503 (2009) [c] Hannemann et al., Phys Rev A 74 pp. 012505 (2006) M. P. Ruffoni - 14th July 2011 - OSA FTS Conference, Toronto

5 High-precision wavelengths for  -variation studies Astronomers searching for possible variations in the fine-structure constant need high-precision absorption line wavenumbers. Many studies have produced null results due to large experimental uncertainties. Newer analyses using many high-precision lab standards suggest a small reduction in  as a function of time. (M. T. Murphy, 2007) M. P. Ruffoni - 4th July 2011 – SPAT Seminar Series

6 New wavenumbers for two important Ti II lines Calibrated by Ar II Calibrated by Mg I, II Calibrated by Ar II Calibrated by Mg I, II Uncertainty in each  is a factor of 2 to 3 times smaller with the Mg I, II standards than with the Ar II standards. M. P. Ruffoni - 14th July 2011 - OSA FTS Conference, Toronto

7 Impact of these results Preliminary calculations on 4 QSOs QuasarRedshift (abs)  with Ti II (x10 -6 )  without Ti II (x10 -6 ) 1J115411+0634261.774-5.1 ± 7.6-6.4 ± 7.7 2J220852-1943591.920-1.5 ± 3.2-4.7 ± 3.2 3J133335+1649031.7768.4 ± 4.58.5 ± 4.5 4J053007-2503292.1406.2 ± 3.6 “In the 4 systems we used, Ti II was very weak. My guess is that we will see benefits in cases where many of the other species are so strong they saturate, but TiII remains optically thin. In those cases Ti II is very likely to be of even greater importance.” M. P. Ruffoni - 4th July 2011 – SPAT Seminar Series

8 Experimentally measured oscillator strengths: J. C. Pickering et al. Can J Phys 89 pp. 387 (2011) Astrophysical spectroscopy in the IR Spitzer Space Telescope Apache Point Observatory Many new IR observatories have appeared in the last decade, with more to follow. NASA’s Spitzer space telescope ESA’s upcoming GAIA mission CRIRES on the Very Large Telescope APOGEE spectrometer in the SDSS III project ScTiVCrMnFeCoNiCuZn –457–2651–4–1 M. P. Ruffoni - 4th July 2011 – SPAT Seminar Series APOGEE is part of the 3 rd Sloane Digital Sky Survey (www.sdss3.org) It will improve our knowledge of galactic evolution Dust obscures visible light. Use IR wavelengths Will measure chemical abundances of 10 5 stars Needs accurate transition probabilities / log(gf)s 2 micron sky survey (2MASS) ScTiVCrMnFeCoNiCuZn –457–2651–4–1 Theory suggests there are 13,000 strong Fe-group transitions between 1.0 and 5.0 mm wavelength (Kurucz, 1995).

9 FTS Branching Fraction Measurements Wavenumber / cm -1 S/N Ratio 6000 7000 8000 9000 10000 Wavenumber / cm -1 5000 15000 20000 25000 30000 No lines in overlap region. Intensity calibration cannot be carried through All lines seen in a single spectrum Most lines seen in 1 st spectrum 2 lines in different region1 line in different region S/N Ratio Ideally, all lines from an upper level are measured in one spectrum and intensity calibrated. More frequently, lines are spaced over 2 or more regions. Lines in overlap region(s) link intensity calibration. 42% 29% 26% 3% M. P. Ruffoni - 4th July 2011 – SPAT Seminar Series

10 H-Band lines for the APOGEE project Branches from two Fe I upper levels taken from Kurucz. Upper level: 7.0 s 6 D7/4f[6] Upper level: 6.0 s 6 D7/4f[5] Cannot use overlapping FTS spectra to span gap between IR and UV / Å log(gf)J lower Config lower J upper Config upper Br. Frac. 1616.50320.4676.0s ( 6 D) 4d e 7 G7.0s ( 6 D) 7/4f[6]0.914 1508.0223-0.9076.0s ( 6 D) 4d e 5 G7.0s ( 6 D) 7/4f[6]0.044 1467.9833-0.9656.0s ( 6 D) 4d e 7 F7.0s ( 6 D) 7/4f[6]0.041 / Å log(gf)J lower Config lower J upper Config upper Br. Frac. 1689.2364-0.4765.0s 6 D 4d e 7 G6.0s 6 D 7/4f[5]0.047 1617.9585-0.2696.0s 6 D 4d e 7 G6.0s 6 D 7/4f[5]0.083 1583.51670.2505.0s 6 D 4d e 7 F6.0s 6 D 7/4f[5]0.285 199.1298-1.2525.0 4 F 4s a 5 F6.0s 6 D 7/4f[5]0.568 M. P. Ruffoni - 14th July 2011 - OSA FTS Conference, Toronto

11 Closing Remarks Our thanks to: G. Nave et al. (NIST) for collaboration on IR measurements J. Lawler et al. (U. Wisconsin) for collaboration on lifetime measurements UK Science and Technology Facilities Council for funding this research For more information: Calibration standards: M. P. Ruffoni et al. ApJ 725 pp. 424 (2010) Oscillator strengths: J. C. Pickering et al. Can J Phys 89 pp. 387 (2011) Atomic spectroscopy at IC: M. P. Ruffoni et al. Proc. NASA LAW (2011) Website: www.sp.ph.ic.ac.uk/~jpickering/FTS E-mail:m.ruffoni@imperial.ac.uk M. P. Ruffoni - 14th July 2011 - OSA FTS Conference, Toronto


Download ppt "New Atomic Data for Astrophysics by High Resolution Fourier Transform Spectrometry l Some technical developments and future challenges M. P. Ruffoni, J."

Similar presentations


Ads by Google