Star Formation and Starburst Galaxies in the Infrared

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Star Formation and Starburst Galaxies in the
Infrared

• Daniela Calzetti (STScI)

199th AAS Meeting, Washington DC, January 9th 2002
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The Unanswered Questions in Star Formation

• What are the regulating mechanisms of SF? What
  determines the intensity, duration (duty cycle)
  and spatial evolution (self-triggering?) of a SF
  event? What is the feedback of SF onto the host
  galaxy?
• How are these mechanisms tied to the global
  properties of the host galaxies?
• How many modes of SF there are?

The answers will also provide recipes for galaxy
evolution models
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Answering requires the study of the age
distributions and SF history of the young stellar
populations in galaxies How to approach the
problem for unresolved pops? N.B. dust-age
degeneracy!
Nuclear region of M83 (D4 Mpc)
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The Impact of Dust Obscuration

• Dust removes 20 -50 of stellar light in
  Local Galaxies
• Regions of star formation are the most
  heavily obscured.

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The Advantage of Multi-l Data
Long baseline discriminates a dusty stellar
population from an ageing one (e.g., U-B as age
indicator)
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Determining Ages and SFHs
Stellar Clusters Diffuse
Population
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What SNAP Can Do

• Multi-l capability discriminates age/dust,
  derives ages
• Spatial resolution HST WFPC2 in the optical and
  HST NICMOS/NIC2 in the IR, plus photometric
  stability resolves individual stellar components
  (e.g., clusters)
• AB29 mag with S/N5 in 10,000 secs detects a
  104 Mo, 10 Myr old cluster at 12.5 Mpc and a 100
  Myr old cluster at 5 Mpc
• Degree (arcmin in IR) FOV Local Galaxies (beyond
  the Local Group) have sizes that range between a
  few arcmin and 30-40 arcmin

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Age Maps
Mapping the SFH of local galaxies will unveil
the nature of the star formation mechanisms as
a function of galactic parameters.
Nuclear region of M83 (Harris et al.
2001)
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Conclusions

• Regulating mechanisms of SF and their dependence
  on global galactic parameters are virtually
  unknown
• Age distributions and SF histories of young
  stellar populations in nearby galaxies will
  provide clues on those mechanisms
• Effective age determinations, for both resolved
  and unresolved populations, require homogeneous
  sets of multi-wavelength data, as those SNAP can
  provide