studying nearby starbursts with hst
DESCRIPTION
Studying Nearby Starbursts with HST. Jason Harris (Steward Observatory) Daniela Calzetti, Jay Gallagher, Denise A. Smith, & Christopher Conselice. Extreme Starbursts :: Lijiang Aug 2005. Star Clusters. Interstellar Medium. Detailed look at the starburst phenomenon. - PowerPoint PPT PresentationTRANSCRIPT
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Studying Nearby Starbursts with HST
Jason Harris (Steward Observatory)
Daniela Calzetti, Jay Gallagher, Denise A. Smith, & Christopher Conselice
QuickTime™ and aDV/DVCPRO - NTSC decompressor
are needed to see this picture.
Extreme Starbursts :: Lijiang Aug 2005
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Nearby Starburst Galaxies
Extreme Starbursts :: Lijiang Aug 2005
• Age and Mass estimates• Star formation history; duration and duty cycle
• Role of interactions• Cluster IMF; specific frequency; dissolution
• Ionization and mechanical heating• Feedback and chemical enrichment• Outflows and infall
Star Clusters
Interstellar Medium
Detailed look at the starburst phenomenon
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Cluster Populations in Starburst Galaxies
Broad-band HST imaging of 3 nearby starbursts
(F300W, F547M, F814W)
Constrain age and mass of each cluster
M 83 NGC 3077 NGC 5253
Extreme Starbursts :: Lijiang Aug 2005
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What happens to a cluster as is ages?
Extreme Starbursts :: Lijiang Aug 2005
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What happens to a cluster as is ages?
Extreme Starbursts :: Lijiang Aug 2005
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What happens to a cluster as is ages?
The two-color diagram
Extreme Starbursts :: Lijiang Aug 2005
If cluster colors can be measured accurately,their ages can be determined
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The Challenge of Cluster Photometry
•Star/cluster classification requires exquisite angular resolution, even for nearby starbursts
•Starburst galaxies typically suffer heavy extinctionincomplete sampling
•Cluster populations are often highly crowdedmakes aperture photometry extremely difficult
•Cluster sizes are variablemakes profile-fitting photometry extremely difficult
•Galaxy backgrounds can be highly variablemakes any photometry more difficult
Extreme Starbursts :: Lijiang Aug 2005
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The Challenge of Cluster Photometry
Aperture Photometry vs. Profile-Fitting Photometry:a hybrid approach
Extreme Starbursts :: Lijiang Aug 2005
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Neighbor-cleaned Aperture Photometry
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Identify groups of non-crowding objects;remove all other objects for “clean” aperture photometry
Extreme Starbursts :: Lijiang Aug 2005
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Extreme Starbursts :: Lijiang Aug 2005
Extinction from Hα/Hβ
NGC 3077 NGC 5253
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Extreme Starbursts :: Lijiang Aug 2005
From Photometry to Mass and Age
Starburst99populationsynthesis models(Leitherer et al. 1999)
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Extreme Starbursts :: Lijiang Aug 2005
Cluster Mass & Age Distributions
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Interstellar Medium
NGC 3077 NGC 5253M 83
Narrow-band HST imaging:[OIII], Hα, [SII]
Extreme Starbursts :: Lijiang Aug 2005
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Hα Morphology
NGC 3077 NGC 5253M 83
Extreme Starbursts :: Lijiang Aug 2005
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log( [SII] / Hα )
Ionization Diagnostics
log( [SII] / Hα )
log(
[OIII]
/ H
β )
log( [SII] / Hα )
NGC 3077
NGC 4214
M 83
NGC 5253
Extreme Starbursts :: Lijiang Aug 2005
Photoionization models by Kewley et al. (2001)
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Mapping the “shock” ionization
Black pixels are “non-photoionization” regions
NGC 3077 NGC 5253M 83
Extreme Starbursts :: Lijiang Aug 2005
200 pc 430 pc 410 pc
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Results & Implications
• Non-photoionized (shocked?) Hα emission accounts for ~ 3%-4% of total emission, ~15%-25% by area.
• Starbursts in dwarfs deposit 70%-100% of mechanical energy in surrounding ISM (within 0.2-1 kpc); may result in
propagating star formation
• Amount of “shocked” gas in dwarfs implies SF duration >> 30 Myr (consistent with cluster/diffuse stellar
ages)
• The starburst in the giant spiral M 83 deposits ~35%-75% of its mechanical energy in the ISM. The shocks are localized
in ‘bubbles’ (no extended shells): confined starburstExtreme Starbursts :: Lijiang Aug 2005
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•Study star-formation processes in nearby starburst galaxies
•Broad-band imaging:
•clusters formed on timescale of few x 107 yr
•in NGC 5253, no clusters older than 20 Myr...efficient destruction?
•very few “Super” star clusters
•Narrow-band imaging:
•non-photoionization accounts for only a few percent of Hα luminosity
•most mechanical energy output from SNe deposited in ISM
•non-photoionized regions in M 83 imply confined starburst
Summary
Extreme Starbursts :: Lijiang Aug 2005