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Searching the missing young stellar population within the Galactic Center. H. Dong, Q. D. Wang, D. Calzetti (umass), A. Cotera (SETI), S. Stolovy, M. Muno, J. Mauerhan (Caltech/IPAC/JPL), C. Lang (U. of Iowa), M. Morris, B. Mills (UCLA), G. Schneider (U. Arizona) Oct 20 th , 2009

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searching the missing young stellar population within the galactic center

Searching the missing young stellar population within the Galactic Center

H. Dong, Q. D. Wang, D. Calzetti (umass), A. Cotera (SETI), S. Stolovy, M. Muno, J. Mauerhan (Caltech/IPAC/JPL), C. Lang (U. of Iowa), M. Morris, B. Mills (UCLA), G. Schneider (U. Arizona)

Oct 20th, 2009

2009 Galactic Center workshop, Shanghai

introduction

2MASS GC image

Introduction
  • GC,~8kpc, the best lab to study the interaction between SMBH and its environment
slide3

Molecular cloud

SMBH

Fuel

SMBH

Star

SMBH

Provide

the energy

introduction1

2MASS GC image

Introduction
  • GC,~8kpc, the best lab to study the interaction between SMBH and its environment
  • Star formation’s effect on the SMBH

Old

molecular

cloud mom

introduction2

2MASS GC image

Introduction
  • GC,~8kpc, the best lab to study the interaction between SMBH and its environment
  • Star formation’s effect on the SMBH
  • Big puzzle: The star formation mode

High T, strong magnetic field (several microgauss) and strong tidal forces!!!!!!!!!!!

Old

molecular

cloud mom

introduction3

Figer et al 1999

2MASS GC image

Introduction
  • GC,~8kpc, the best lab to study the interaction between SMBH and its environment
  • Star formation’s effect on the SMBH
  • Big puzzle: The star formation mode
  • Three clusters within GC, Arches, Quintuplet and Center

How do they form!!!!!!

the key questions
The Key Questions
  • How do the clusters form?
the key questions1
The Key Questions
  • How do the clusters form?
  • What are their properties?
    • Arches and Center show top-heavy IMF (Stolte et al. 2005, Paumard et al 2006)
the key questions2
The Key Questions
  • How do the clusters form?
  • What are their properties?
  • How do they shape the ISM within GC
the key questions3
The Key Questions
  • How do the clusters form?
  • What are their properties?
  • How do they shape the ISM within GC
  • The star formation history within GC

More young star clusters are needed !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

hst galactic center pa survey
HST Galactic Center Pa α Survey
  • Why Pa α ?
    • Trace the young stellar population directly, low stellar background
    • In the near-IR band
    • 3-4 times brighter than Brγ, even with the strong extinction
  • Why HST/NICMOS NIC3?
    • High Angular resolution, ~0.2”
    • Large Field View~1’ ×1’
    • Low instrument background
    • Without the affect from atmosphere
    • Stable PSF
slide12

HST Galactic Center Pa α Survey

  • HST/NIC3
  • F187N (on line) and F190N (off line)
  • MULTI-ACCUM exposures
  • 4-point half pixel dithering, large spatial shifts (6.09”) among dithering exposures
  • 192 s per each position and filter
slide13

Arches

Sgr A*

Quintuplet

144 orbits, ~416 arcmin^2, systematic around Sgr A*

~15’, 35 pc

Spitzer 8 micron dust only image (PAH), from Susan Stolovy

~39’, 90 pc

slide14

F187 Mosaic

F190 Mosaic

source detection
Source Detection
  • ‘Starfinder’, ~0.6 million point sources
  • 50% completeness limit varies from 80 uJy (17.5 mag) to 500 uJy (15.5 mag)
  • 85% star light in F190N have been resolved
result 1 which kind of sources we are looking on
Result 1: Which kind of sources we are looking on
  • Magnitude distribution
  • Defining foreground sources with F1.87/F1.90>1.07, i.e. H-K<1
  • The peak around 15.5 should not be due to the detection limit
  • What is the origin of this component?????
result 1 which kind of sources we are looking at
Result 1: Which kind of sources we are looking at
  • Padova Stellar track (Girardi et al. 2000)
  • ATLAS 9 atmosphere model (Castelli et al. 1997)
result 1 which kind of sources we are looking on2
Result 1: Which kind of sources we are looking on
  • The bright stellar peak around 15.5 magnitude represents AGB/RGB with 1-3 solar mass
  • They distribute in a disk-like structure
  • Sjouwerman et al 1999, OH/IR masers, median expansion velocities, a starburst activities > 1 Gyr ago
result 3 pa emitting sources the tracer of the missing star clusters
Result 3: Pa αemitting sources – the tracer of the missing star clusters
  • Massive stars in the transient phase, such as, O If, Luminous Variable Blue (LBV), Wolf-Rayet (WN and WC)
  • Selecting out Pa αemitting sources by considering the local extinction and photometric error
  • ~160 sources
  • We recover most of the spectroscopy identified massive stars within the three clusters (~65 sources)
  • Most of them are WN and OIf, then WC, and 3 WNE
slide24

Star formation doesn’t constrain on the three massive star

clusters!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

summary
Summary
  • We construct the first big mosaic of the Pa αemission within GC with high angular resolution~0.2”
  • We detect 0.6 million sources
  • We found the RGB/AGB in the nuclear disk
  • 160 Pa αsources have been detected, 50% are outside of the three well know star clusters
  • Many new extended emissions
future work
Future Work
  • Compared with the Padova stellar mode to understand the age and star formation history of the nuclear disk
  • Construct an extinction map
  • Reconstruct the stellar distribution model of the nuclear disk and nuclear bulge
  • Study the stellar properties of the new HII regions
  • The properties of the ISM in the ionization fronts
collaborators

Collaborators

Caltech

Susan Stolovy

Jon Mauerhan

Solange Ramirez

Michael Muno

Umass

Daniel Wang

Daniela Calzetti

SETI

Angela Cotera

Arizona

Glenn Schneider

UCLA

Mark Morris

Betsy Mills

Univ. of Iowa

Cornelia Lang

introduction4

2MASS GC image

Introduction
  • GC, the best place to study the interaction between SMBH and its environment

GC

M31

the key questions4

Cotera et al 1999

The Key Questions
  • How do the clusters form?
  • What are their properties?
  • How do they shape the ISM within GC
data analysis

Demonstration for one position, left: using our method, right: using the traditional ‘Pedsub’ method

Data Analysis
  • Basic pipeline
    • Overlap field, global solution to correct the relative background and astrometry among exposures, positions and orbits
data analysis1
Data Analysis
  • Basic pipeline
  • Source Detection
    • Creating the PSF from 42 brightest sources
    • ‘Starfinder’, ~0.6 Million point sources
    • 50% completeness limit varied from 80 uJy (17.5 mag) to 500 uJy (15.5 mag)
    • 85% star light in F190N have been resolved
data analysis2
Data Analysis
  • Basic pipeline
    • Overlap field, global solution to correct the relative background and astrometry among exposures, positions and orbits
slide36

Foreground molecular clouds

F187 Mosaic

F190 Mosaic

data analysis3
Data Analysis
  • Basic pipeline
    • Overlap field, global solution to correct the relative background and astrometry among exposures, positions and orbits
    • Absolute background, foreground molecular clouds
    • Absolute astrometry, 11 SiO Masers
data analysis4
Data Analysis
  • Basic pipeline
  • Source Detection
    • ‘Starfinder’, ~0.6 million point sources
    • 50% completeness limit varies from 80 uJy (17.5 mag) to 500 uJy (15.5 mag)
    • 85% star light in F190N have been resolved
data analysis5
Data Analysis
  • Basic pipeline
  • Source Detection
  • ‘Varial Scale method’ (Scoville et al 2003) to produce the Pa α image for each position
    • Creating a ratio map
result 1 which kind of sources we are looking on3
Result 1: Which kind of sources we are looking on
  • Magnitude distribution
  • Defining foreground sources with F1.87/F1.90>1.07, i.e. H-K<1
  • The peak around 15.5 should not due to the detection limit
  • What is the origin of this component?????
result 3 pa emitting sources the tracer of the missing star clusters1
Result 3: Pa αemitting sources – the tracer of the missing star clusters
  • 60% are within the well know three clusters, 40% are field
  • More sources in the left side
  • Most of these sources should not belong to the three massive star clusters
  • Dynamics information are needed for these sources