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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