NGC 4330 Recap & LateStage Addi6ons to Paper Anne Abramson - - PowerPoint PPT Presentation

NGC 4330 Recap & Late‐Stage Addi6ons to Paper

Anne Abramson June 16, 2010

Paper Recap

• Morphological Features
• Derived Evolu6onary Timescales
• Stripping History

Morphological Tracers of RPS

• ISM trunca6on along major axis
• Extraplanar HI
• UV major axis asymmetry
• The Upturn
• The Tail
• Extraplanar UV Regions

Morphological Tracers of RPS

• ISM trunca6on along major axis

HI, dust ex6nc6on stripped to well within undisturbed old stellar disk (50 – 65% of R_25)

Morphological Tracers of RPS

• One‐sided extraplanar HI – 32% total

downwind, 10% in tail

Morphological Tracers of RPS

• UV major axis asymmetry

Recent SF highly truncated on leading side, less so on trailing side;

• ngoing SF symmetric about center

Indicates change in spa6al distribu6on of SF regions within last ~10 Myr

Morphological Tracers of RPS

• The Upturn – striking,

hitherto undocumented morphological feature indicates virtually all ISM removed from disk by ram pressure

Morphological Tracers

• f RPS
• The Tail – ISM removed from

disk has formed tail, ISM has been displaced downwind

• ver past 10 – 200 Myr

Morphological Tracers of RPS

• Extraplanar UV Regions – SF in stripped gas
• ver past ~350 Myr (most within past 100

Myr)

Derived Evolu6onary Timescales

• Leading

Edge: 200 – 400 Myr to strip from >8 – 5 kpc

• Trailing Side:

No age gradient

Derived Evolu6onary Timescales

• Tail Evolu6on: 10 –

300 Myr for ISM to move downwind from UV/Hα to current posi6on

Derived Evolu6onary Timescales

• Extraplanar UV regions – all formed <400 Myr

ago

Stripping History

• RP increased rapidly ~200 – 400 Myr ago
• Gas stripped from >8 – 5 kpc on leading side
• Disk stripped asymmetrically ‐ more deeply on

leading side than trailing side (traced by UV)

• Ader ~1 rota6onal period (400 Myr), gas now

more symmetric (traced by HI and Hα)

• Within past ~400 Myr, gas has led the trailing

side of the disk to form the base of the tail, tail has con6nued to move from disk

Late‐Stage Addi6ons

• Current form of SP models
• Thoughts on crea6on of thick disk

Late‐stage Addi6on ‐ Treatment of SP Models

Open boxes: parameter space made possible by nested doughnut correc7on Filled circles/boxes: measured values

Reminder: Nested Doughnut Correc6on

Late‐stage Addi6on ‐ Crea6on of Thick Disk

• In 4330 we observe recent SF that has
• ccurred outside the thin disk

In stripped extraplanar gas In tail – downwind of disk plane

Late‐stage Addi6on ‐ Crea6on of Thick Disk

• In 4330, recent SF has occurred outside the thin

disk

• Most stars close enough to the galaxy to remain

bound

• These will create new halo components – in some

cases, the dis6nc6on between the thick disk and halo will be arbitrary

• Thick disks made by mergers are older than their

embedded thin disks; thick disks made by RPS are younger than their thin disks & have narrow range of stellar ages

Predicted Thick Disk Proper6es

• Over a few dynamical 6mes, will spread out to disk of

thickness ~2 kpc, radius ~12 kpc, stellar age range few x 100 Myr

Major axis ~2 kpc ~12 kpc

Data vs. Models