Megan Johnson - Green Bank

Report
Mapping the HI Neighborhood
Around Starburst Dwarf Galaxies
Megan Johnson
NRAO, Green Bank
Tully-Fisher Workshop, April 2012
Outline
• Introduction
• NGC 1569
– Review of stellar and gas kinematics from
LITTLE THINGS
– GBT map
• NGC 4163/NGC 4214
• Future Work
• Summary
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Introduction
• Starburst = short-lived intense period of star
formation that is unsustainable over the Hubble
time due to the limited supply of gas within a
galaxy (McQuinn + 2010); generally,
interactions/mergers are triggers
• Dwarf Galaxy = low luminosity, low mass system,
contained in a dark matter halo; believed to be the
“Building Blocks” of larger galaxies
• Starburst Dwarf Galaxy = possibly a “Building
Block” in action? What is the role of
interactions/mergers between dwarf galaxies?
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Introduction
• Can HI environment around starburst
dwarf galaxies provide clues to their
interaction/merger history?
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NGC 1569 –
What is its
shape?
• Stellar and
Gas Kinematics
 Vmax/σz
A
B
• Member of IC 342 Galaxy Group
• D = 3.36 Mpc (Grocholski + 2008)
• MV = -17.57
• SFR = 0.24 M/yr
• HI mass = 2.5 x 108 M
• Stellar mass = 2.8 x 108 M
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Previous Work:
“HI Companion,”
“HI Bridge,” Stil &
Israel (1998) and
“NCM HI Cloud” –
Stil & Israel (2002)
- HV3
“Chimney” Hunter et al.
(1993); Mühle et
al. (2005);
Westmoquette et
al. (2008)
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Stellar Kinematics
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Position-Velocity Diagrams – Stars
and Gas
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Ionized Gas in NGC 1569
B
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A
9
Stellar Velocity Dispersions
<σz> = 21 ± 4 km/s
Constant
SSC B SSC A
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Bulk Motion Extraction
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Bulk Motion Extraction
Bulk VF
Strong
NCM
Vmax = 50 ± 10 km/s
Weak
NCM
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Strong
+ Weak
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Rotation Curve of NGC 1569
Vmax = 50 ± 10 km/s
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Baryonic TF Relation –
Trachternach+ 2009
Total Baryonic Mass
= 6.8 x 108 M
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★
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NGC 1569
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GBT Map around NGC 1569
NGC 1569
UGCA 92
Southern HI Extension
-113.17 km/s
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GBT Map around NGC 1569
NGC 1569
UGCA 92
MW Cloud
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Intergalactic Filaments
-110.76 km/s
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NGC 4163
• Member of Canes Venatici
Cloud
• D = 2.8 Mpc
• MV = -14.37
• SFR = 9.1 x 10-4 M/yr
• HI mass = 1.4 x 107 M
• Stellar mass = 2.7 x 107 M
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NGC 4163 – IWM Velocity Field
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NGC 4214
• D = 2.9 Mpc
• MV = -17.56
• SFR = 0.13 M/yr
• HI mass = 5.8 x 108 M
• Stellar mass = 4.8 x 108 M
• Member of Canes Venatici Cloud
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NGC 4214 – IWM Velocity Field
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Integrated HI GBT Map
UGCA 7605
RMS = 25 mK,
(at 1σ
in a 1 km/s
channel)
UGCA 7559
UGCA 7599
NGC 4214
NGC 4163
NGC 4244
NGC 4190
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What about field dwarfs?
• Are nearby dwarf irregular galaxies still
assembling?
• GBT proposal to map all LITTLE THINGS
dwarfs
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IC 1613 – Local Group Member
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DDO 165 – M81 Group Member
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DDO 46 – No Known Group
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Summary
• NGC 1569 is a thick disk
– Vmax/σz = 2.4 ± 0.7
– Stars and gas kinematically follow each other
– Extended HI emission to south and northeast of
NGC 1569 in VLA map stretching in the direction of
UGCA 92 and confirmed with GBT
• NGC 4163/4214
– “Unsettled” HI in VLA maps
– Possible extended emission detected in GBT map …
stay tuned …
• LITTLE THINGS - ??
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Ultra-dense HI Cloud (UDHIC)
Hα tail –
Velocity ~ -90
km/s (Tomita
et al. 1994)
Integrated HI Intensity Contour Map
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