1 / 15

Photometric System

Photometric System. ASTR 3010 Lecture 14 Textbook Ch.10. History of Photometry. Ptolemy & Tycho : by eyes, ~0.5mag 19 th century: naked eyes, ~0.3mag late 19 th century: photometer, ~0.25mag early 20 th century: photograph, ~0.03mag 1940s: photomultiplier tube, ~0.005mag

millie
Télécharger la présentation

Photometric System

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Photometric System ASTR 3010 Lecture 14 Textbook Ch.10

  2. History of Photometry • Ptolemy & Tycho: by eyes, ~0.5mag • 19th century: naked eyes, ~0.3mag • late 19th century: photometer, ~0.25mag • early 20th century: photograph, ~0.03mag • 1940s: photomultiplier tube, ~0.005mag • late 20th century: CCD, ~0.01mag • present: Kepler, ~0.00001mag  transiting planets.

  3. Response Function • Bandpass: a range of wavelengths where an instrument is sensitive • single-band photometry: e.g., Kepler. Time series • broadband multi-color photometry: shape of the spectrum, ultra low resolution spectroscopy. “broad” = Δλ/λ > 10%. “Color”=color index, brightness and color. • narrow- & intermediate band photometry: to isolate a specific line, molecular band, etc., E.g., Balmer discontinuity, TiO band, Hα, etc.

  4. Features relevant to narrowband photometry

  5. Filters • determined by the combined spectral response of various sources (filter, detector, atmosphere, & telescope). E.g., Johnson-U • bandpass filter • high-pass filter • low-pass filter • neutral density filter

  6. Response Function • bandwidth (W0) • λpeak • λcen

  7. Effective Wavelength

  8. Color correction • Large survey with several passbands (e.g., all-sky survey) • Measurements with the same filter result in different λeff • Assume a certain source spectrum shape. color correction λ λcat

  9. Isophotal wavelength Bandpass measurement equivalent to a measurement of the monochromatic flux at a certain wavelength times the bandpass

  10. Color indices Difference b/w two magnitudes ≈ slope of spectra ≈ Blackbody temperature color index = m (shorter λ) - m (longer λ) • all indices should be zero for Vega  “Vega system” or “Vega magnitudes”

  11. Discontinuity, line strength, etc. Usually, two band magnitudes are sufficient to quantify these…

  12. Line index line index = mnarrow – mwide Good example = Hα young star survey

  13. Curvature index (X-C) > 0 for emission (X-C) < 0 for absorption

  14. Planet imaging filter • Spectral Differencing Imaging (SDI)

  15. In summary… Important Concepts Important Terms effective wavelength isophotal wavelength filter bandpass • Color correction • filter response function • Kind of • Chapter/sections covered in this lecture : 10.1-10.3

More Related