ay122a week1 - california institute of technologyay122a& • instructors:& –...
TRANSCRIPT
Ay122a
Week 1: Units, backgrounds, ground-‐based
observing considera:ons
Ay122a • Instructors:
– Dimitri Mawet (1?? Cahill, x1452, dmawet@astro) – Chuck Steidel (252 Cahill, x4168, ccs@astro) – no TA, so come and talk to us! – Class website: hOp://www.astro.caltech.edu/~dmawet/ay122 (will be up over the weekend)
• Class requirements: – Homeworks (3-‐4 problem sets) 40%
• Standard Caltech collabora:on policy: you may discuss the problems with your classmates but you must write your own solu:ons independently
– Paper+talk (due last week of classes) 30% • More details as soon as we bring up the web page (this weekend)
– Final exam (30%) • Take-‐home variety, during exam period in Dec.
SOFIA (2.7m telescope on board specially-‐equipped Boeing 747)
“Op:cal” (0.3-‐1 micron) Filters
Standard filters for use in calibra:ons rela:ve to Vega, but not really intui:ve for anything but stars at z=0
SDSS filter system: § “square” bandpasses § AB calibra:on
§ e.g., m(u’)-‐m(r’)=0 means constant flux density in fν units
hOp://www.astronomy.ohio-‐state.edu/~mar:ni/usefuldata.html
Standard stars: Landolt (1992) AJ,104,340 (op:cal) Persson et al 1998, AJ, 116,2475 (NIR)
Y J H K Ks
Ground-‐based Filters IR broad-‐band filters are designed to match the atmospheric windows
Spitzer/IRAC Filters
WISE Filters (all-‐sky survey)
Op$cal Sky Background Signal from the sky background is present in every pixel. Because each instrument generally has a different pixel scale, the sky brightness is usually tabulated for a site in units of mag/arcsecond2.
˝ (mag/ 2)
Lunar age
(days)U B V R I
0 22.0 22.7 21.8 20.9 19.93 21.5 22.4 21.7 20.8 19.97 19.9 21.6 21.4 20.6 19.710 18.5 20.7 20.7 20.3 19.514 17.0 19.5 20.0 19.9 19.2
NaD OH
Hg
OH can be resolved
Zodiacal light
atmosphere
IR Sky Backgrounds
Line intensi:es vary on :mescales of ~20-‐200s (as well as spa:ally)
Sky Background Variation Tests
17
(P200/Triplespec 220 x 600s exposures over 5 nights in April 2009
Wavelength
time
11 April 2011 MOSFIRE PSR v1.5
Sky Background Variation Tests
18
(P200/Triplespec 220 x 600s exposures over 5 nights in April 2009
H-band continuum spectral pixel vs. time (e-/sec) OH line pixel vs. time (e-/sec)
11 April 2011 MOSFIRE PSR v1.5
Infrared Sky and Thermal Background
Galac:c 100 micron “Cirrus” Emission (IRAS satellite, 1980s)
Ex:nc:on Curves