1. Disturbed Things Come in small packages
Jessica V. Bloom
Disturbed Things Come in small packages
Thanks to:
Scott Croom
Julia Bryant
Joss Bland-Hawthorn

2. Kinematics can uncover processes shaping galaxy evolution
Kinematic classification of SAMI galaxies
Physical basis for scatter off the Tully-Fisher relation
What determines asymmetry?
Bloom et al., 2016 (submitted)
Events which perturb kinematics (e.g. major/minor mergers, secular processes) play key role in galaxy evolution
Morphology valuable, but kinematics allows different view, without Hubble type or bursts of SFR
Low mass galaxies are known to be highly irregular – work on TFR etc
Test case for different kinds/causes of asymmetry
Shapiro et al., 2008

3. Data SAMI Galaxy Survey data cubes
Hα emission line kinematic maps fit by LZIFU
(Ho et al., 2014) – subsample of 816 galaxies
MY SAMPLE: 532 galaxies after Hα S/N cuts
Gas kinematics, range of morphological types, thanks to I-Ting Ho, Institute for Astronomy, University of Hawaii
Explain colours/velocity fields

4. HIGHER MODES INDICATES KINEMATIC ASYMMETRY
Krajnovic et al., 2007
KINEMETRY
Asymmetry (n>1)
POWER IN
HIGHER MODES INDICATES KINEMATIC ASYMMETRY
Regular rotation
Fourier decomposition of velocity fields, such that they are separated into modes, with asymmetry signatures carried in higher order modes
Fits first and higher order models to velocity and dispersion fields
Take the median over ellipses

5. Classification using kinemetry
Visually classified normal galaxies
Bloom et al., 2016 (submitted)
Bin counts (normalised)
Visually classified perturbed galaxies

6. Scatter off the Tully-Fisher Relation (can be physically explained)
Asymmetry
Causes:
TFR remains at all stellar masses
PA offset
SCATTER OFF TFR
INVERSELY CORRELATES WITH
STELLAR MASS
Increases with scatter, decreases with mass
Low Vrot
- explain TFR
Previous work, e.g. Kannapan et al., in Nearby Field Galaxy Survey
Thanks to Luca
Poorly constrained PA (due to mergers making the galaxy irregular)
Large offset between photometric and kinematic PA (yay for spatially resolved kinematics!)
– correlation between PA offset and scatter off TFR, as well as
- inverse correlation between PA offset and stellar mass
What this tells us: PA offset is a major cause of scatter below TFR, particularly at low stellar mass
Scatter increases at low mass
log(Stellar Mass)
Vrot measurements by
L. Cortese

7. Asymmetry is related to stellar mass
Asymmetry-mass correlation:
Slope=-0.27,
p-value=5.8x10-8
GAS ASYMMETRY IS
INVERSELY CORRELATED WITH MASS
No trend with Halpha S/N and mass
No trend with coverage and asymmetry
Gas fraction linked to formation of massive instabilities – low mass galaxies have high gas fractions
High gas fraction also linked to turbulent support, relative to rotational support
Also maybe environmental – satellites?
log(Stellar Mass)

8. Why are asymmetry and mass anticorrelated?
Interactions?
Are low mass galaxies satellites of large galaxies?
Are low mass galaxies qualitatively different?
High gas fraction  turbulence, star formation…
More likely to be
kinematically disturbed
Less likely

9. What about distance to nearest neighbour?
GAMA: Liske et al., 2015
Brough et al., 2013
DN = distance to first nearest neighbour
AT ALL DN,
LOW MASS GALAXIES
HAVE HIGHER
GAS ASYMMETRY
log(M*)<9.0
log(M*)>10.0:
Slope =-0.18, p-value=0.009
Stellar mass
- Thanks to Sarah
STRESS MEDIANS NOT TREND LINES
High and not high are separate distributions (something is going to that is different for both of them)
May tell us that interaction causes asymmetry in high mass galaxies, but something else is going on for low mass galaxies
log(M*)>10.0
log(M*)<9.0:
Slope=-0.063, p-value=0.49
DN measurements by S. Brough

10. Disturbed things trend small
Stellar mass is more strongly related to asymmetry than distance to nearest neighbour
Asymmetry can be caused by turbulence, bursty star formation
Interaction is not the primary cause of asymmetry
Scatter off the Tully-Fisher relation can be explained
Scatter is often caused by offset between photometric and kinematic PA

11. Differences in PA  rotation velocity
Kinematic PA
Photometric PA