1 / 5

PI: Suzanna Randall Total Time: 300 hours

Estimating the Ages of Nearby Elliptical Galaxies from the Spectroscopic Analysis of Hot Evolved Stars in M 32. PI: Suzanna Randall Total Time: 300 hours

kieu
Download Presentation

PI: Suzanna Randall Total Time: 300 hours

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Estimating the Ages of Nearby Elliptical Galaxies from the Spectroscopic Analysis of Hot Evolved Stars in M 32 PI:Suzanna Randall Total Time: 300 hours CoI’s: of order 10 stellar population synthesis people, experts in the spectroscopy of crowded fields and atmospheric modelling, stellar evolution theorists

  2. Scientific Rationale • Abrupt rise rise in the UV continuum emission of elliptical galaxies between 1200 and 2000 Å discovered in 1969 • Puzzling for a long time, the excess UV flux is now thought to originate principally from hot evolved (horizontal branch and post-horizontal branch) stars • However, the relative flux contribution from different types of hot evolved stars is debatable, and has a critical impact on the age, metallicity and evolutionary history of the galaxy UV upturn O’Connell, 1999

  3. Scientific Rationale Two main hypotheses: 1) Metal-poor:UV-upturn due to a very old metal-poor population - requires uncomfortably large age (up to 20 Gyrs) Z=0.06, 10 Gyrs Z=0.01, ~18 Gyrs 2) Metal-rich:results from an old metal-rich population - requires a number of assumptions, including an age ~ 10 Gyrs => If we know the characteristics and relative flux contribution of the stars making up the UV excess, we can constrain the age of the galaxy

  4. Immediate Objective • We propose to obtain UBV photometry for the 25’x25’ field observed in the UV by STIS/HST in M32 (Brown et al. 2000), and use this to construct a colour-magnitude diagram down to V~29 • From the photometry we will select of order 1000 hot evolved stars and obtain low-resolution spectroscopy • We will model the individual spectra with appropriate model atmospheres, and determine their evolutionary status (EHB, post AGB, post-early AGB, AGB Manqué) and atmospheric parameters • The measured relative abundance of different types of star will be an invaluable input for evolutionary models, finally solve the UV-upturn debate that has been raging for four decades, and ultimately lead to a robust age estimate for nearby elliptical galaxies

  5. Justification • The vast majority of the UV-bright sources detected in M32 are fainter than 26th magnitude and we expect extreme horizontal branch stars to be as faint as V~29 (Mv~4.5) in this galaxy, requiring an ELT-class telescope even for low S/N (~5) low-resolution (R~500) spectroscopy • We require a large field-of-view (~25’x25’) multi-object spectrograph (~1000 slits) with a high efficiency in the blue part of the optical spectrum, and AO to get a spatial resolution of ~1” (!) • This will be the first time that evolved hot stars have been spectroscopically classified in an external galaxy, making the data invaluable from a galaxy morphology, evolution and dynamics point of view

More Related