Download FEEDBACK IN THE LOCAL UNIVERSE: The

Sravani Vaddi1, Chris O’Dea1, Stefi Baum1, Christine Jones 2,
Bill Forman2, Samantha Whitmore 3 and Rabeea Ahmed3
1Astrophysical
Sciences & Technology, RIT
2Harvard-Smithsonian
3Harvard
SRAVANI VADDI, RIT
Center for Astrophysics
University
AGN - Active Galactic Nucleus
• AGN - Class of galaxies
showing energetic phenomena
at the center of the galaxy.
• Proposed by Hoyle and
Fowler(1963).
Fig: AGN Model
SRAVANI VADDI, RIT
MULTI-WAVELENGTH IMAGES OF AGN
12
Chapter 1. Introduction
INFRARED
Hydra A galaxy
SRAVANI VADDI, RIT
Figure 1.5: The 100 kpc-scale supercavity system in Hydra A. Wise et al. (2007) estimate that the
radio source has returned upwards of 1061 erg to regions of the cluster that extend even beyond the
cooling radius. Note the strong spatial anti-correlation of the radio source (in pink) with the X-ray
cavities (in blue). Such correspondence is typical of cool core clusters with cavities and extended
radio sources, presenting strong circumstantial evidence in support of the AGN feedback model.
Centaurus A galaxy. Credit: X-ray: Chandra; Radio: VLA; Optical: ESO
MOTIVATION
Observations
Theory
Faint
But observations indicate
that there are very few
bright galaxies.
Number density
Bright
Some mysterious energy
is
preventing
star
formation.
Galaxy brightness
Fig: Galaxy Luminosity Function. Simply a distribution of galaxies
Credit: Simon Driver
SRAVANI VADDI, RIT
Theory predicts large
number
of
bright/massive galaxies.
12
POSSIBLE SOLUTION – AGN FEEDBACK
Chapter 1. Introduction
• Jets from the AGN
prevent cooling of the
gas by pushing away
the gas.
• This reduces
formation.
Figure 1.5: The 100 kpc-scale supercavity system in Hydra A. Wise et al. (2007) estimate that the
radio source has returned upwards of 1061 erg to regions of the cluster that extend even beyond the
cooling radius. Note the strong spatial anti-correlation of the radio source (in pink) with the X-ray
cavities (in blue). Such correspondence is typical of cool core clusters with cavities and extended
radio sources, presenting strong circumstantial evidence in support of the AGN feedback model.
See Bîrzan et al. (2004) for a comprehensive census of the currently known X-ray cavity systems
in groups and clusters of galaxies. (Credit: X-ray: NASA/CXC/U.Waterloo/C.Kirkpatrick et al.;
Radio: NSF/NRAO/VLA; Optical: Canada-France-Hawaii-Telescope/DSS).
SRAVANI VADDI, RIT
star
Hydra A. Credit: X-ray: Chandra Telescope;
Radio: VLA; Optical: Canada-France-HawaiiTelescope
THE PROJECT
AGN feedback is observed in distant galaxies.
THEN,
 Is it still ongoing?
 How powerful is AGN activity in the nearby
galaxies?
 How does it affect star formation in these
galaxies if at all it does?
SRAVANI VADDI, RIT
RESULT 1 – RADIO POWER AND GALAXY MASS
RELATION
Maximum radio power from the
AGN is dependent on the mass of
the galaxy.
Massive galaxies are capable of
hosting powerful radio sources.
This is consistent with AGN
feedback shaping the high mass
end of galaxy LF.
SRAVANI VADDI, RIT
CONCLUSION & FUTURE WORK
CONCLUSION
•
We notice that AGN feedback is ongoing in the local universe.
•
AGN activity is not very powerful and prominent in the nearby galaxies as compared to
distant galaxies.
•
AGN activity does seem to influence star formation via feedback, BUT, it is not the only
process involved in reducing star formation.
FUTURE WORK
•
How much feedback is affecting star formation. What are the other processes?
•
Quantitative analysis for this work needs to be done such as calculating star formation
rate, efficiency of accretion.
SRAVANI VADDI, RIT