Browsing by Author "Privon, George"

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    The Arp 240 Galaxy Merger: A Detailed Look at the Molecular Kennicutt-Schmidt Star Formation Law on Subkiloparsec Scales
    (IOP Publishing Ltd, 2025) Saravia, Alejandro; Rodas Quito, Eduardo; Barcos Muñoz, Loreto; Evans, Aaron; Kunneriath, Devaky; Privon, George; Song, Yiqing; Yoon, Ilsang; Emig, Kimberly L.; Sánchez Garcia, María; Linden, Sean; Green, Kara Noelle; Johnstone, Makoto; Nagarajan Swenson, Jaya; Meza, Gabriela A.; Momjian, Emmanuel; Armus, Lee; Charmandaris, Vassilis; Díaz Santos, Tanio; Treister, Ezequiel
    The molecular Kennicutt-Schmidt Law has been key for understanding star formation (SF) in galaxies across allredshifts. However, recent subkiloparsec observations of nearby galaxies reveal deviations from the nearly unityslop e(N) obtained with disk-averaged measurements. We study SF and molecular gas (MG) distribution in theearly-stage luminous infrared galaxy merger Arp 240(NGC 5257-8). Using Very Large Array radio continuum (RC) and Atacama Large Millimeter/submillimeter Array CO(2-1)observations at 500 pc scale, with a uniformgrid analysis, we estimate SF rates and MG surface densities (Sigma(SFR) and H-2, respectively). In Arp 240,Nissublinear at 0.52 +/- 0.17. For NGC 5257 and NGC 5258,Nis 0.52 +/- 0.16 and 0.75 +/- 0.15, respectively. Weidentify two SF regimes: high surface brightness (HSB) regions in RC with N similar to 1, and low surface brightness (LSB) regions with shallow N (ranging 0.15 +/- 0.09-0.48 +/- 0.04). Median CO(2-1) linewidth and MG turbulent pressure (P-turb) are 25 km s(-1) and 9 x 10(5) K cm(-3). No significant correlation was found between Sigma(SFR) and CO(2-1) linewidth. However, Sigma(SFR) correlates with P-turb, particularly in HSB regions (rho>0.60). In contrast, SF efficiency moderately anticorrelates with P-turb in LSB regions but shows no correlation in HSB regions. Additionally, we identify regions where peaks in SF and MG are decoupled, yielding a shallow N (<= 0.28 +/- 0.18). Overall, the range of N reflects distinct physical properties and distribution of both the SF and MG, which can be masked by disk-averaged measurements.
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    Warm Molecular Hydrogen in Nearby, Luminous Infrared Galaxies
    (2018) Petric, Andreea O.; Armus, Lee; Flagey, Nicolas; Guillard, Pierre; Howell, Justin; Inami, Hanae; Charmandaris, Vassillis; Evanss, Aaron; Stierwalt, Sabrina; Diaz-Santos, Tanio; Lu, Nanyao; Spoon, Henrik; Mazzarella, Joe; Appleton, Phil; Chan, Ben; Chu, Jason; Hand, Derek; Privon, George; Sanders, David; Surace, Jason; Xu, Kevin; Zhao, Yinghe
    Mid-infrared molecular hydrogen (H-2) emission is a powerful cooling agent in galaxy mergers and in radio galaxies; it is a potential key tracer of gas evolution and energy dissipation associated with mergers, star formation, and accretion onto supermassive black holes. We detect mid-IR H-2 line emission in at least one rotational transition in 91% of the 214 Luminous Infrared Galaxies (LIRGs) observed with Spitzer as part of the Great Observatories All-sky LIRG Survey. We use H-2 excitation diagrams to estimate the range of masses and temperatures of warm molecular gas in these galaxies. We find that LIRGs in which the IR emission originates mostly from the Active Galactic Nuclei (AGN) have about 100 K higher H-2 mass-averaged excitation temperatures than LIRGs in which the IR emission originates mostly from star formation. Between 10% and 15% of LIRGs have H-2 emission lines that are sufficiently broad to be resolved or partially resolved by the high-resolution modules of Spitzer's Infrared Spectrograph (IRS). Those sources tend to be mergers and contain AGN. This suggests that a significant fraction of the H-2 line emission is powered by AGN activity through X-rays, cosmic rays, and turbulence. We find a statistically significant correlation between the kinetic energy in the H-2 gas and the H-2 to IR luminosity ratio. The sources with the largest warm gas kinetic energies are mergers. We speculate that mergers increase the production of bulk inflows leading to observable broad H-2 profiles and possibly denser gas.