Ay 21 Slides - Jan 14ccs/Ay21/Ay21_2020jan14_slides.pdf · Kennicutt 1992, ApJS 79, 255 Ca H,K+...
Transcript of Ay 21 Slides - Jan 14ccs/Ay21/Ay21_2020jan14_slides.pdf · Kennicutt 1992, ApJS 79, 255 Ca H,K+...
Ay 21 Slides - Jan 14
http://star-www.st-and.ac.uk/~spd3/Teaching/AS3011/AS3011_5.pdf
http://star-www.st-and.ac.uk/~spd3/Teaching/AS3011/AS3011_5.pdf
Problems With Traditional Galaxy Classification Appearance of galaxies is strongly dependent on whichwavelength the observations are made in.
X-ray UV Visible Near-IR Far-IRNote: large change in appearance between the UV and the near infrared images.
e.g., the nearby galaxy M81:
Galaxies look “clumpier” in the UV, and increasingly smoothas we go to the visible and longer wavelengths.
4
GalaxyLuminosityFunctionBingelli,Sandage,andTammann1988ARAA2650
Credit: NASA/STScI- Hubble Ultra-Deep Field
http://www.bo.astro.it/~eps/templates/ff06.jpg
GalaxySpectralEnergyDistributionsvs.HubbleType
Light from young stars
Kennicutt1992,ApJS79,255
CaH,K+“4000Abreak”
CH~4300A
MgI+molec.~5170A
NaI
Early-Type (E) Galaxies: integrated stellar light
ProminentNebularEmissionLines(rest-frameoptical)
[OII]3727,3729Ratiosensitivetoelectrondensity,strongathighmetallicity
[OIII]4959,5007Ratiofixed(1:3)but[OIII]/Hβsensitivetoionizingsource;strongestlineforZ<0.6Z◉
Hα/Hβ(6564/4861)Firstcountsionizingphotons,ratioshouldbe~2.9intheabsenceofreddening/extinction
[NII](6549,6585)Ratiooftwolinesfixed(1:3)but[NII]/Hαsensitivetometallicity
[SII](6717,6731)Ratiosensitivetoelectrondensity
Kennicutt1992,ApJS79,255
Hα+[NII](6564,6585)
[SII](6718,6732)
Balmerseriesabs
[OII]3727
Typical Spiral Galaxies (MW-like)
[SII]6717,6731
[OII]3727
Hβ,[OIII]4959,5007
Hα+[NII]
Irregular Galaxies- Strongly Star-Forming