Young Stellar Populations in the Ultraviolet Claus Leitherer (STScI)
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8/18/2010 Claus Leitherer: Young Stellar Populations 1 Young Stellar Populations in the Ultraviolet Claus Leitherer (STScI)
description
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
Transcript of Young Stellar Populations in the Ultraviolet Claus Leitherer (STScI)
8/18/2010Claus Leitherer:
Young Stellar Populations 1
Young Stellar Populations in the Ultraviolet
Claus Leitherer (STScI)
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o M83: Chandar et al. (2010)
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Topics
o New UV Models for Young Populations
o Probing the nearby and distant galaxies with UV Lines
o Open Issues
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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)
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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
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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
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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
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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
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o Fit to FOS+GHRS template: standard Kroupa/Salpeter IMF
Nuclear Star Clusters in M83 (Wofford et al. 2010)
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OPTICAL HST/WFC3
FUV HST/STIS
M83: Ages from UV Spectra
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M83: Ages from Photometry
o Chandar et al. (2010) & the WFC3 SOC
o Age-reddening degeneracy
o Breaking the degeneracy with H
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M83: Results
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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)
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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
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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
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o Erb et al. (2010)
o restframe UV spectrum of BX418
o Young, metal-poor galaxy at z = 2.3
o He II 1640!
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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
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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
