Revision of Galaxy SEDs with New Stellar Models

Transcription

1 Revision of Galaxy SEDs with New Stellar Models Claus Leitherer (STScI) 11/18/08 Claus Leitherer: Revision of Galaxy SEDs 1

2 Use galaxy SED for the determination of stellar content, i.e., SFR(t) or M Analysis of galactic M/L Variables: IMF, dust, chemistry, stellar SED, stellar M/L Use stellar structure and evolution models to relate stellar L and M 11/18/08 Claus Leitherer: Revision of Galaxy SEDs 2

3 New Rotating Evolution Models Star-forming galaxies massive stars Previously: stellar evolution completely determined by chemical composition, stellar mass, mass-loss rate Now: stellar rotation becomes fundamental ingredient (Maeder & Meynet 2000) Why? Evidence from surface abundance anomalies, lifetimes of evol. phases, stellar number ratios 11/18/08 Claus Leitherer: Revision of Galaxy SEDs 3

4 Effects of rotation: modifies hydrostatic structure induces mixing affects mass loss Consequences: larger convective core higher luminosity lower surface opacity higher effective temperature How does this affect the theoretical M/L of a population? Implementation of new evolution models into Starburst99 (Vázquez et al. 2007) 11/18/08 Claus Leitherer: Revision of Galaxy SEDs 4

5 60 M! star with Z = 10-5 Z! ; v rot = 0 (left) and 300 km s -1 (right) Ekström et al. (2009) 11/18/08 Claus Leitherer: Revision of Galaxy SEDs 5

6 Vázquez et al. (2007) Evolution of a 60 M! star Red/solid: prior 1992/94 tracks Blue/dotted: new models with rotation 11/18/08 Claus Leitherer: Revision of Galaxy SEDs 6

7 Implementation into Starburst99 Attach model atmospheres and/or empirical stellar libraries UCL models for O and WR stars Fold in an IMF (Salpeter from 1 to 100 M! ) Calculate SED Combine with photoionization models for emission-line spectrum (Kewley, Levesque; in progress) 11/18/08 Claus Leitherer: Revision of Galaxy SEDs 7

8 Ionizing luminosities vs. age Singular burst, solar composition, 10 6 M! 912, 504, and 228 continua Red/full: prior Blue/dotted: new 11/18/08 Claus Leitherer: Revision of Galaxy SEDs 8

9 Panchromatic luminosities vs. age Same parameters as before New models favor the RSG phase 11/18/08 Claus Leitherer: Revision of Galaxy SEDs 9

10 L Bol /M, L V /M, and L K /M vs. age Same parameters as before 11/18/08 Claus Leitherer: Revision of Galaxy SEDs 10

11 Main trends in single stellar populations: Higher luminosities at all wavelengths Effect stronger at shorter wavelengths (factor of 3 in the H ionizing continuum!) Near-IR stronger due to increase of RSGs Influence of rotation increases with decreasing metallicity (higher rotation velocity) 11/18/08 Claus Leitherer: Revision of Galaxy SEDs 11

12 Implications for SF Indicators Impact of new evolution models on steady-state populations Determine relations between panchromatic luminosities and SFR Salpeter IMF from 1 to 100 M! 11/18/08 Claus Leitherer: Revision of Galaxy SEDs 12

13 SFR [M! yr 1 ] = N LyC [s 1 ] SFR [M! yr 1 ] = L 1500 [erg s 1 Å 1 ] SFR [M! yr 1 ] = L V [erg s 1 Å 1 ] SFR [M! yr 1 ] = L FIR [erg s 1 ] SFR [M! yr 1 ] = 50 ν core-collapse [yr 1 ] 11/18/08 Claus Leitherer: Revision of Galaxy SEDs 13

14 SFR [M! yr 1 ] = N LyC [s 1 ] SFR [M! yr 1 ] = N LyC [s 1 ] SFR [M! yr 1 ] = L 1500 [erg s 1 Å 1 ] SFR [M! yr 1 ] = L 1500 [erg s 1 Å 1 ] SFR [M! yr 1 ] = L V [erg s 1 Å 1 ] SFR [M! yr 1 ] = L V [erg s 1 Å 1 ] SFR [M! yr 1 ] = L FIR [erg s 1 ] SFR [M! yr 1 ] = L FIR [erg s 1 ] SFR [M! yr 1 ] = 50 ν core-collapse [yr 1 ] SFR [M! yr 1 ] = 52 ν core-collapse [yr 1 ] Z = Z! 11/18/08 Claus Leitherer: Revision of Galaxy SEDs 14

15 SFR [M! yr 1 ] = N LyC [s 1 ] SFR [M! yr 1 ] = N LyC [s 1 ] SFR [M! yr 1 ] = L 1500 [erg s 1 Å 1 ] SFR [M! yr 1 ] = L 1500 [erg s 1 Å 1 ] SFR [M! yr 1 ] = L V [erg s 1 Å 1 ] SFR [M! yr 1 ] = L V [erg s 1 Å 1 ] SFR [M! yr 1 ] = L FIR [erg s 1 ] SFR [M! yr 1 ] = L FIR [erg s 1 ] SFR [M! yr 1 ] = 50 ν core-collapse [yr 1 ] SFR [M! yr 1 ] = 49 ν core-collapse [yr 1 ] Z = 0.2 Z! 11/18/08 Claus Leitherer: Revision of Galaxy SEDs 15

16 Main Points Rotation increases the luminosity and effective temperature of massive stars. The rotation velocity increases with decreasing metallicity. Applied to synthetic population SEDs, L/M becomes larger. The effect is strongest at the shortest wavelengths and lowest metallicity. The Lyman continuum output may increase by up to a factor of 3 and the spectrum hardens. 11/18/08 Claus Leitherer: Revision of Galaxy SEDs 16

17 Rotation essentially introduces a free parameter and makes synthesis modeling less deterministic 11/18/08 Claus Leitherer: Revision of Galaxy SEDs 17