ASTR633 Astrophysical Techniques Course slides Chapter 5: - PowerPoint PPT Presentation

ASTR633 Astrophysical Techniques Course slides Chapter 5: Photometry (note: we’re not covering polarimetry — see book if you’re interested)

Spectral Energy Distributions and Spectra Andrews et al. 2012, ApJ

Aperture photometry https://astrobites.org/2016/04/15/astroimagej-a-simple-and-powerful-tool-for-astronomical-image-analysis-and-precise-photometry/

What is the “right” aperture size? King 1971, PASP

The need for PSF photometry https://www.eso.org/public/usa/images/eso9953a/

Photometric systems (optical) Figure 1 Schematic passbands of broad-band systems. Bessell 2005 Ann. Reviews

Photometric systems (infrared) Bessell 2005 Ann. Reviews

TABLE 2 Isophotal, Effective, Mean, and Pivot Wavelengths for the MKO-NIR Filters l iso l eff l eff � l 0 l pivot Filter ( m m) ( m m) ( m m) ( m m) ( m m) J ....... 1.250 1.241 1.243 1.248 1.247 H ....... 1.644 1.615 1.619 1.630 1.628 K � ...... 2.121 2.106 2.111 2.123 2.121 K s ...... 2.149 2.138 2.141 2.151 2.150 K ....... 2.198 2.186 2.190 2.202 2.200 L ....... 3.754 3.717 3.727 3.757 3.752 � M ...... 4.702 4.680 4.681 4.684 4.684 � Tokunaga & Vacca 2005 PASP

Converting between different systems The observed flux density (magnitude) will di ff er from one telescope/camera to another due to the system response and also on the color of the object Red object Blue object

Pan-STARRS Photometric System and SDSS, Johnson / Cousins (Vega), and 2MASS (Vega). Both 3.2. Stellar Color Transformations linear and quadratic versions are provided, with coefficients We used the synthetic magnitudes from the SEDs to fit for conversions between the Pan-STARRS1 photometric system y = A 0 + A 1 x + A 2 x 2 = B 0 + B 1 x. (6) Table 6 Pan-STARRS1 Bandpass Transformations x y A 0 A 1 A 2 ± B 0 B 1 ± ( g − r ) SDSS ( g P 1 − g SDSS ) − 0.011 − 0.125 − 0.015 0.006 − 0.012 − 0.139 0.007 ( g − r ) SDSS ( r P 1 − r SDSS ) 0.001 − 0.006 − 0.002 0.002 0.000 − 0.007 0.002 ( g − r ) SDSS ( i P 1 − i SDSS ) 0.004 − 0.014 0.001 0.003 0.004 − 0.014 0.003 ( g − r ) SDSS ( z P 1 − z SDSS ) − 0.013 0.040 − 0.001 0.009 − 0.013 0.039 0.009 ( g − r ) SDSS ( y P 1 − z SDSS ) 0.031 − 0.106 0.011 0.023 0.031 − 0.095 0.024 ( g − r ) SDSS ( w P 1 − r SDSS ) 0.018 0.118 − 0.091 0.012 0.012 0.039 0.025 ( B − V ) ( g P 1 − B ) − 0.108 − 0.485 − 0.032 0.011 − 0.104 − 0.523 0.013 ( B − V ) ( r P 1 − V ) 0.082 − 0.462 0.041 0.025 0.077 − 0.415 0.025 ( B − V ) ( r P 1 − R C ) 0.117 0.128 − 0.019 0.008 0.119 0.107 0.009 ( B − V ) ( i P 1 − I C ) 0.341 0.154 − 0.025 0.012 0.343 0.126 0.013 ( J 2MASS − H 2MASS ) ( z P 1 − J 2MASS ) 0.418 1.594 − 0.603 0.068 0.428 1.260 0.073 ( J 2MASS − H 2MASS ) ( y P 1 − J 2MASS ) 0.528 0.962 − 0.069 0.061 0.531 0.916 0.061 ( g − r ) P 1 ( g SDSS − g P 1 ) 0.013 0.145 0.019 0.008 0.014 0.162 0.009 ( g − r ) P 1 ( r SDSS − r P 1 ) − 0.001 0.004 0.007 0.004 − 0.001 0.011 0.004 ( g − r ) P 1 ( i SDSS − i P 1 ) − 0.005 0.011 0.010 0.004 − 0.004 0.020 0.005 ( g − r ) P 1 ( z SDSS − z P 1 ) 0.013 − 0.039 − 0.012 0.010 0.013 − 0.050 0.010 ( g − r ) P 1 ( z SDSS − y P 1 ) − 0.031 0.111 0.004 0.024 − 0.031 0.115 0.024 ( g − r ) P 1 ( r SDSS − w P 1 ) − 0.024 − 0.149 0.155 0.018 − 0.016 − 0.029 0.031 ( g − r ) P 1 ( B − g P 1 ) 0.212 0.556 0.034 0.032 0.213 0.587 0.034 ( g − r ) P 1 ( V − r P 1 ) 0.005 0.462 0.013 0.012 0.006 0.474 0.012 ( g − r ) P 1 ( R C − r P 1 ) − 0.137 − 0.108 − 0.029 0.015 − 0.138 − 0.131 0.015 ( g − r ) P 1 ( I C − i P 1 ) − 0.366 − 0.136 − 0.018 0.017 − 0.367 − 0.149 0.016 ( g − r ) P 1 ( V − w P 1 ) − 0.021 0.299 0.187 0.025 − 0.011 0.439 0.035 ( g − r ) P 1 ( V − g P 1 ) 0.005 − 0.536 0.011 0.012 0.006 − 0.525 0.012 Note. The table provides the coefficients for Equation (6). Tonry et al. 2012, ApJ

Atmospheric extinction C. Buton et al.: Mauna Kea atmospheric extinction properties Fig. 17. Mean SN  atmospheric extinction (solid line) and its physical components (dashed lines). For comparison we overplot the previous Mauna Kea extinction measures derived by Boulade (1987) (diamonds), Bèland et al. (1988) (triangles) and Krisciunas et al. (1987) (stars). Buton et al (2013, A&A, 549, A8)

CFHT Cloudcams http://www.cfht.hawaii.edu/en/gallery/cloudcams

http://www.cfht.hawaii.edu/Instruments/Elixir/skyprobe/tonight.html

Calibration practices • 10-20% accuracy: use standard values for extinction • ~1-5% accuracy: ‣ observe standard stars close in airmass and time to your science target ‣ observe standards close in color to your target ‣ note that if you have SDSS, PS1, or 2MASS standards in your images, you can calibrate directly from your science data without taking separate calibration images • <1% accuracy: measure a variety of di ff erent color standards at a variety of airmasses throughout the night. Very large overhead so needs to be science- driven.

Magnier et al. 2013, ApJ

Scatter of bright stars in uber-calibrated data (griz filters) g i r z (magnitudes) Magnier et al. 2013, ApJ

Aumann et al. 1984 Vega is not a blackbody… The first time I remember a newspaper article on a scientific discovery

Vega is not a blackbody…