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RE: NGC 2146
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Title: A far-IR view of the starburst driven superwind in NGC 2146
Author: K. Kreckel, L. Armus, B. Groves, M. Lyubenova, T. Diaz-Santos, E. Schinnerer, P. Appleton, K. V. Croxall, D. A. Dale, L. K. Hunt, P. Beirao, A. D. Bolatto, D. Calzetti, J. Donovan Meyer, B. T. Draine, J. Hinz, R. C. Kennicutt, S. Meidt, E. J. Murphy, J. D. T. Smith, F. S. Tabatabaei, F. Walter

NGC 2146, a nearby luminous infrared galaxy (LIRG), presents evidence for outflows along the disk minor axis in all gas phases (ionized, neutral atomic and molecular). We present an analysis of the multi-phase starburst driven superwind in the central 5 kpc as traced in spatially resolved spectral line observations, using far-IR Herschel PACS spectroscopy, to probe the effects on the atomic and ionized gas, and optical integral field spectroscopy to examine the ionized gas through diagnostic line ratios. We observe an increased ~250 km/s velocity dispersion in the [OI] 63 micron, [OIII] 88 micron, [NII] 122 micron and [CII] 158 micron fine-structure lines that is spatially coincident with high excitation gas above and below the disk. We model this with a slow ~200 km/s shock and trace the superwind to the edge of our field of view 2.5 kpc above the disk. We present new SOFIA 37 micron observations to explore the warm dust distribution, and detect no clear dust entrainment in the outflow. The stellar kinematics appear decoupled from the regular disk rotation seen in all gas phases, consistent with a recent merger event disrupting the system. We consider the role of the superwind in the evolution of NGC 2146 and speculate on the evolutionary future of the system. Our observations of NGC 2146 in the far-IR allow an unobscured view of the wind, crucial for tracing the superwind to the launching region at the disk center, and provide a local analog for future ALMA observations of outflows in high redshift systems.

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Posts: 131433
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The Ruby Ring
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Title: The Snapshot Hubble U-band Cluster Survey; A cluster complex in NGC 2146
Authors: Angela Adamo, Linda J. Smith

We present the Snapshot Hubble U-band Cluster Survey (SHUCS), an ongoing deep U-band imaging survey of nearby star-forming galaxies. Thanks to the information provided by the U band, together with archival Hubble Space Telescope (HST) optical data, we are able to constrain reliable ages, masses, and extinctions of the cluster populations of these galaxies. We show some preliminary results from the study of one of the SHUCS galaxies, NGC 2146. Using the recovered cluster ages we try to understand the propagation of the star formation in one of the tidal streams where a ring-like cluster complex has been found. The Ruby Ring, so named due to its appearance, shows a clear ring-like distribution of star clusters around a central object. We find evidence of a spatial and temporal correlation between the central cluster and the clusters in the ring. The Ruby Ring is the product of an intense and localised burst of star formation, similar to the extended cluster complexes observed in M 51 and the Antennae, but more impressive because is quite isolated. We discuss the formation of the Ruby Ring in a "collect & collapse" framework. The predictions made by this model agree quite well with the estimated bubble radius and expansion velocity produced by the feedback from the central cluster, making the Ruby Ring an interesting case of triggered star formation.

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Posts: 131433
Date:
NGC 2146
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Title: Revealing a Ring-like Cluster Complex in a Tidal Tail of the Starburst Galaxy NGC 2146
Authors: A. Adamo, L. J. Smith, J. S. Gallagher, N. Bastian, J. Ryon, M. S. Westmoquette, I. S. Konstantopoulos, E. Zackrisson, S. S. Larsen, E. Silva-Villa, J. C. Charlton, D. R. Weisz

We report the discovery of a ring-like cluster complex in the starburst galaxy NGC 2146. The Ruby Ring, so named due to its appearance, shows a clear ring-like distribution of star clusters around a central object. It is located in one of the tidal streams which surround the galaxy. NGC 2146 is part of the Snapshot Hubble U-band Cluster Survey (SHUCS). The WFC3/F336W data has added critical information to the available archival Hubble Space Telescope imaging set of NGC 2146, allowing us to determine ages, masses, and extinctions of the clusters in the Ruby Ring. These properties have then been used to investigate the formation of this extraordinary system. We find evidence of a spatial and temporal correlation between the central cluster and the clusters in the ring. The latter are about 4 Myr younger than the central cluster, which has an age of 7 Myr. This result is supported by the H alpha emission which is strongly coincident with the ring, and weaker at the position of the central cluster. From the derived total H alpha luminosity of the system we constrain the star formation rate density to be quite high, e.g. ~ 0.47 Msun/yr/kpc^2. The Ruby Ring is the product of an intense and localised burst of star formation, similar to the extended cluster complexes observed in M51 and the Antennae, but more impressive because is quite isolated. The central cluster contains only 5 % of the total stellar mass in the clusters that are determined within the complex. The ring-like morphology, the age spread, and the mass ratio support a triggering formation scenario for this complex. We discuss the formation of the Ruby Ring in a "collect & collapse" framework. The predictions made by this model agree quite well with the estimated bubble radius and expansion velocity produced by the feedback from the central cluster, making the Ruby Ring an interesting case of triggered star formation.

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