Week 1Overview of High EnergyAstrophysicsMake things as simple as possible, but no simpler - A. EinsteinKeep an open mind, but not so open that your brains fall out - My PhD advisor
Blackbody RadiaGon•Eγ=hν•Energy distribuGon independent of material(iron, aluminum, sodium, alloy…)•Peak in energy distribuGon related to Temp–νmax= 1011(T/K) Hz of energy distribuGon–λmaxT= 3x106nm*K•EmiSance ( =Power/area), grows rapidly withTemp–Power/area=σT4:Stefan-Boltzmann Law
There is a wide range offrequencies emiSed by BBThere are relaGvely morehigh frequencies emiSedthan lowSun T~6000K,νmax~green,but enGre spectrum lookswhite-yellow due to slightabsorpGon and scaSering ofblue-green light.
Light: The BroaderElectromagnetic Spectrum
balloonsSpace StaGon=350kmFermi, Hubble = 550kmIf all objects in sky emiSed likeblackbodies, as our sun and stars(approximately), thenPrior to looking, Radio, Millimeterwas seen as domain of coldobjects, likely uninteresGngThis could not be farther from thetruthAt radio frequencies below 10MHz, the ionosphere reﬂects radiowaves. This is why CB (Ham) cantalk to people all over the earth…
CR electrons emi`ngsynchrotron as they circle inB fieldsLMCQuasar3C273CrabRadio provides precise angular resoluGon so jet of 3C273 could be imaged, and source ofjet was much smaller than host galaxy. First evidence of massive black hole, 108M_sun
21 cm All-Sky: NeutralHydrogenTransiGon is highly forbidden, so once it happens, H takea long Gme to decay back to ground state (107yr!). Byuncertainty principle,ΔEΔt~h, the uncertainty of the lineis relaGvely narrow, and deviaGons from expectedenergy are likely due to Doppler shih.Tool to study interstellar gas structure: clouds, filaments, loopsTool to study velocity distribuGon of galaxies to distances far beyond edge of starlight
Redshih Z~10Hydrogen gas too cold to emitmuch 21 cm light, so look forabsorpGon of CMB light at thiswavelength by neutral HydrogenabsorpGon line disappears aherre-ionizaGon21 cm corresponds to 1.4 GHz andthen redshihed down to 140MHz.