Massive Star Clusters in Non-Interacting Galaxies Dynamical Mass Estimates and the (I)MF Søren S. Larsen ESO / ST-ECF, Garching Tom Richtler, Concepcion Jean P. Brodie, UCO / Lick Deidre A. Hunter, Lowell See also: Larsen & Richtler, A&A, in press (astro-ph/0407610) Larsen, Brodie & Hunter, AJ, in press (astro-ph/0407373)
11
Embed
Massive Star Clusters in Non-Interacting Galaxies Dynamical Mass Estimates and the (I)MF
Massive Star Clusters in Non-Interacting Galaxies Dynamical Mass Estimates and the (I)MF. Søren S. Larsen ESO / ST-ECF, Garching. Tom Richtler, Concepcion Jean P. Brodie, UCO / Lick Deidre A. Hunter, Lowell. See also: Larsen & Richtler, A&A, in press ( astro-ph/0407610 ) - PowerPoint PPT Presentation
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
Massive Star Clusters in Non-Interacting Galaxies
Dynamical Mass Estimates and the (I)MF
Søren S. LarsenESO / ST-ECF, Garching
Tom Richtler, Concepcion Jean P. Brodie, UCO / Lick Deidre A. Hunter, Lowell
See also:Larsen & Richtler, A&A, in press (astro-ph/0407610)
Larsen, Brodie & Hunter, AJ, in press (astro-ph/0407373)
Motivation• “Massive” (104-106 M) young star clusters have been
found in several nearby galaxies• Appear similar to old globular clusters in terms of
sizes and masses, but will they really evolve into bona-fide old (~1 Hubble time) GCs?
• One key question is the (I)MF shape - if deficient in low-mass stars, clusters might disrupt prematurely
• Is IMF universal, or are there variations? Direct observations of low-mass stars generally unfeasible beyond Local Group => dynamical M/L ratios of YMCs represent one way to constrain IMF
M/L ratios and IMFs for YMCs
Mengel et al. 2002, A&A 383, 137SSP models from Leitherer et al. 1999 (Starburst99; 0.1 - 100 M)
M/L ratios from high-dispersion spectroscopy and HST imaging
• HST imaging: cluster profiles well resolved (1 WFPC2 pixel ~ 1.5 pc at 3 Mpc)
• VLT/UVES and Keck/HIRES/NIRSPEC echelle spectroscopy => velocity dispersions through cross-correlation analysis (Tonry & Davis 1979)
Target galaxiesNGC 6946
NGC 5236
NGC 4449
NGC 4214
Cluster sizes: EFF Model Fits
Sizes determined with baolab/ishape software (Larsen 1999).Convolves TinyTim PSF with Elson, Fall & Freeman (EFF) models of the form P(r) ~ [1-(r/rc)2]-
F555W
Residuals
Velocity dispersions
Keck/HIRES spectra
Velocity dispersion: vx2 = TC 2 - TT
2
where TC and TT are the dispersions of the cluster-template and template-template CCFs (Tonry & Davis 1979)
Notes: 1) No individual strong lines are required for this technique to work. 2) Intrinsic broadening of lines (macroturbulence etc.) “cancels out”.