8/18/2010 Claus Leitherer: Young Stellar Populations 1 Young Stellar Populations in the Ultraviolet Claus Leitherer (STScI)
Young Stellar Populations in the Ultraviolet Claus Leitherer (STScI)
Feb 24, 2016
Young Stellar Populations in the Ultraviolet Claus Leitherer (STScI). M83: Chandar et al. (2010). Topics. New UV Models for Young Populations Probing the nearby and distant galaxies with UV Lines Open Issues. New UV Models for Young Populations. - PowerPoint PPT Presentation
Welcome message from author
This document is posted to help you gain knowledge. Please leave a comment to let me know what you think about it! Share it to your friends and learn new things together.
Transcript
8/18/2010Claus Leitherer:
Young Stellar Populations 1
Young Stellar Populations in the Ultraviolet
Claus Leitherer (STScI)
8/18/2010Claus Leitherer:
Young Stellar Populations 2
o M83: Chandar et al. (2010)
8/18/2010Claus Leitherer:
Young Stellar Populations 3
Topics
o New UV Models for Young Populations
o Probing the nearby and distant galaxies with UV Lines
o Open Issues
8/18/2010Claus Leitherer:
Young Stellar Populations 4
New UV Models for Young Populations
o Goal: model UV spectra of nearby and distant young populations
o Stellar initial mass function (IMF) and SF historyo Stellar evolution models (conversion of mass into
luminosity and introduction of the time-scale)o Spectral libraries (empirical and theoretical)o 2nd order parameters (reddening, geometry)
8/18/2010Claus Leitherer:
Young Stellar Populations 5
Modeling wind and photospheric lines with WM-Basic:
Leitherer et al. (2010a)
o Non-LTE, spherically extended, blanketed radiation-hydrodynamics code for hot stars
o Pauldrach et al. (2001)o Accounts for wind instabilities
and resulting shocks for modeling the wind lines
o All Starburst99 UV spectra are now fully theoretical
o Allows models for any Z, /Fe, etc.
o Wind lines of NV 1240, SiIV 1400, CIV 1550 trace stars with M > 30 Msol IMF
8/18/2010Claus Leitherer:
Young Stellar Populations 6
Probing Galaxies with UV Lines
o Modeling the UV spectra of different classes of objects over a range of distances and spatial scales
o Distances: ~2 Mpc to z 3o Individual star clusters and galaxy diskso Sizes of ~1 pc to >kpco Super-solar to extreme sub-solar Z
8/18/2010Claus Leitherer:
Young Stellar Populations 7
o Shapley et al. (2003): composite of ~1000 LBGs
o Integrated over galaxy disk
o Z 0.4 Zsolo Stellar vs.
interstellar lines
o IMF very close to Kroupa/Salpeter
Modeling rest-frame UV spectra of Lyman-break galaxies
8/18/2010Claus Leitherer:
Young Stellar Populations 8
o Space-UV observations
o D = 2 – 50 Mpco ~ tens of pc coverageo A few…..many clusters
and SF regions in aperture
o Composite of all FOS+GHRS spectra in the HST archive (Leitherer et al. 2010b)
UV spectra of local galaxies observed with HUT/ FUSE/HST
8/18/2010Claus Leitherer:
Young Stellar Populations 9
o Fit to FOS+GHRS template: standard Kroupa/Salpeter IMF
Nuclear Star Clusters in M83 (Wofford et al. 2010)
8/18/2010Claus Leitherer:
Young Stellar Populations 10
1 2
14
45
6 789
12
1113
3
109 7
4
14
1
5
23
1012
6
11
13
8
1” : 20 pc
OPTICAL HST/WFC3
FUV HST/STIS
M83: Ages from UV Spectra
8/18/2010Claus Leitherer:
Young Stellar Populations 11
M83: Ages from Photometry
o Chandar et al. (2010) & the WFC3 SOC
o Age-reddening degeneracy
o Breaking the degeneracy with H
8/18/2010Claus Leitherer:
Young Stellar Populations 12
M83: Results
8/18/2010Claus Leitherer:
Young Stellar Populations 13
o ages – masses – reddening
o Spectroscopic and photometric ages agree within 20% if H is used
o Oldest clusters are the most massive (selection effect in spectroscopy)
o Few clusters with ages over ~100 Myr (photometry)
8/18/2010Claus Leitherer:
Young Stellar Populations 14
Outliers and Open Issues
o Wolf-Rayet stars (some – but not all – are the evolved end product of massive stars)
o Missing ingredients in stellar evolution
8/18/2010Claus Leitherer:
Young Stellar Populations 15
o NGC 3125-1: Wolf-Rayet cluster in a BCDo Strongest He II 1640 emission known in a local SF galaxyo IMF biased towards massive stars?o Overly strong He II 1640 also observed in LBGs
8/18/2010Claus Leitherer:
Young Stellar Populations 16
o Erb et al. (2010)
o restframe UV spectrum of BX418
o Young, metal-poor galaxy at z = 2.3
o He II 1640!
Claus Leitherer: Young Stellar Populations
178/18/2010
o Effects of Rotation: modifies hydrostatic structure induces mixing affects mass loss
o Consequences: larger convective core higher luminosity lower surface opacity higher effective temperature
o Affects the mass-luminosity relation of a population
o Related effect: mass transfer in Close Binaries
8/18/2010Claus Leitherer:
Young Stellar Populations 18
Take-Away Pointso Stellar UV lines offer the most direct probe of
massive stars in integrated galaxy spectrao Stellar atmosphere/wind models are
sufficiently mature to provide spectra for galaxies at low and high redshift
o On average, SF galaxies follow a Kroupa/Salpeter IMF
o Stellar evolution models are the weak link (rotation, binaries) and require significant future effort
Related Documents
