mapping the hi neighborhood around starburst dwarf galaxies

Mapping the HI Neighborhood Around Starburst Dwarf Galaxies

Megan JohnsonNRAO, 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?

5

A

B

NGC 1569 – What is its

shape?

• 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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• Stellar and Gas

Kinematics Vmax/σz

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“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)

Previous Work:

Stellar Kinematics

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Position-Velocity Diagrams – Stars and Gas

Ionized Gas in NGC 1569

B A

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Stellar Velocity Dispersions

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<σz> = 21 ± 4 km/s

SSC B SSC A

Constant

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Bulk Motion Extraction

Vmax = 50 ± 10 km/s

Bulk Motion Extraction

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Bulk VFStrong NCM

WeakNCM

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

★ NGC 1569Total Baryonic Mass = 6.8 x 108 M

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GBT Map around NGC 1569

-113.17 km/s

UGCA 92

NGC 1569Southern HI Extension

GBT Map around NGC 1569

-110.76 km/s

Intergalactic Filaments

MW Cloud

UGCA 92NGC 1569

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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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UGCA 7605

UGCA 7559

UGCA 7599

NGC 4244

NGC 4214

NGC 4163

NGC 4190

Integrated HI GBT Map

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RMS = 25 mK, (at 1σin a 1 km/s channel)

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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

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 - ??April 2, 2012 26Megan Johnson - TF 35

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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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