Tuesday, 4/30/13

And 5 papers today, because, well, they were all interesting!
1) Full CO J=3-2 map of M51 by Vlahakis et al., using HARP-B on the JCMT. They study low-J CO line variations both in arm and inter-arm regions and radially. Also, apparently 8micron PAH surface brightness correlates really well with CO(3-2) intensity.
2) High-redshift molecular ISM overview in a invited talk proceeding by Riechers. Could be a good overview of high-z molecular stuff for those of us who are generally only more local…
3) A huge ARAA review on the coevolution (or not) of SMBHs and their host galaxies. Looks like a whopper… By Kormendy & Ho.
4) Little atomic hydrogen blobs apparently outflowing from the center of our own galaxy. These guys are 15pc, observed up to 700pc away. The abstract doesn’t reveal how exactly they connect them to an outflow, but it sounds interesting. By McCure-Griffiths et al.
5) Are PAHs really PAHs? A paper suggesting that the mid-IR bands might instead be ‘mixed aromatic/aliphatic structures’. By Kwok & Zhang.

Title: A CO J=3-2 map of M51 with HARP-B: Radial properties of the spiral structure
Authors: Vlahakis, C.; van der Werf, P.; Israel, F. P.; Tilanus, R. P. J.
Publication: eprint arXiv:1304.7408
Publication Date: 04/2013
Origin: ARXIV
Keywords: Astrophysics – Cosmology and Extragalactic Astrophysics, Astrophysics – Galaxy Astrophysics
Comment: 26 pages, 18 figures, 7 tables
Bibliographic Code: 2013arXiv1304.7408V


We present the first complete CO J=3-2 map of the nearby grand-design spiral galaxy M51 (NGC 5194), at a spatial resolution of ~600 pc, obtained with the HARP-B instrument on the James Clerk Maxwell Telescope. The map covers the entire optical galaxy disk and out to the companion NGC 5195, with CO J=3-2 emission detected over an area of ~9’x6′ (~21×14 kpc). We describe the CO J=3-2 integrated intensity map and combine our results with maps of CO J=2-1, CO J=1-0 and other data from the literature to investigate the variation of the molecular gas, atomic gas and polycyclic aromatic hydrocarbon (PAH) properties of M51 as a function of distance along the spiral structure on sub-kpc scales. We find that for the CO J=3-2 and CO J=2-1 transitions there is a clear difference between the variation of arm and inter-arm emission with galactocentric radius, with the inter-arm emission relatively constant with radius and the contrast between arm and inter-arm emission decreasing with radius. For CO J=1-0 and HI the variation with radius shows a similar trend for the arm and inter-arm regions, and the arm-inter-arm contrast appears relatively constant with radius. We investigate the variation of CO line ratios (J=3-2/2-1, J=2-1/1-0 and J=3-2/1-0) as a function of distance along the spiral structure. Line ratios are consistent with the range of typical values for other nearby galaxies in the literature. The highest CO J=3-2/2-1 line ratios are found in the central ~1 kpc and in the spiral arms and the lowest line ratios in the inter-arm regions.We find no clear evidence of a trend with radius for the spiral arms but for the inter-arm regions there appears to be a trend for all CO line ratios to increase with radius. We find a strong relationship between the ratio of CO J=3-2 intensity to stellar continuum-subtracted 8mu PAH surface brightness and the CO J=3-2 intensity that appears to vary with radius.

Title: Physical Conditions in the Interstellar Medium of High-Redshift Galaxies: Mass Budget and Gas Excitation
Authors: Riechers, Dominik A.
Publication: eprint arXiv:1304.7286
Publication Date: 04/2013
Origin: ARXIV
Keywords: Astrophysics – Cosmology and Extragalactic Astrophysics
Comment: 11 pages, 7 figures, invited talk paper, to appear in NRAO Conference Series, "The Interstellar Medium in High Redshift Galaxies Comes of Age" (a workshop in honor of Paul Vanden Bout), 13-15 September 2012, Charlottesville, Virginia, USA
Bibliographic Code: 2013arXiv1304.7286R


Following the first pioneering efforts in the 1990s that have focused on the detection of the molecular interstellar medium in high redshift galaxies, recent years have brought great advances in our understanding of the actual physical properties of the gas that set the conditions for star formation. Observations of the ground-state CO J=1-0 line have furnished crucial information on the total masses of the gas reservoirs, as well as reliable dynamical mass and size estimates. Detailed studies of rotational ladders of CO have provided insight on the temperature and density of the gas. Investigations of the very dense gas associated with actively star-forming regions in the interstellar medium, most prominently through HCN and HCO+, have enabled a better understanding of the nature of the extreme starbursts found in many high-redshift galaxies, which exceed the star formation rates of their most active present-day counterparts by an order of magnitude. Key progress in this area has been made through targeted studies of few, well-selected systems with current facilities. With the completion of the Karl G. Jansky Very Large Array and the Atacama Large (sub)Millimeter Array, it will become possible to develop a more general framework for the interpretation of these investigations based on unbiased studies of "normal" star-forming galaxies back to the earliest cosmic epochs.

Title: Coevolution (Or Not) of Supermassive Black Holes and Host Galaxies
Authors: Kormendy, John; Ho, Luis C.
Publication: eprint arXiv:1304.7762
Publication Date: 04/2013
Origin: ARXIV
Keywords: Astrophysics – Cosmology and Extragalactic Astrophysics
Comment: 136 pages, 38 postscript figures, 4 tables; requires cittable.tex, psfig.tex, annrev4K-E.tex; accepted for publication in Volume 51 (2013) of Annual Review of Astronomy and Astrophysics; Supplementary Information will be submitted to arXiv separately in approximately 2013 June
Bibliographic Code: 2013arXiv1304.7762K


We review the observed demographics and inferred evolution of supermassive black holes (BHs) found by dynamical modeling of spatially resolved kinematics. Most influential was the discovery of a tight correlation between BH mass and the velocity dispersion of the host-galaxy bulge. It and other correlations led to the belief that BHs and bulges coevolve by regulating each other’s growth. New results are now replacing this simple story with a richer and more plausible picture in which BHs correlate differently with different galaxy components. BHs are found in pure-disk galaxies, so classical (elliptical-galaxy-like) bulges are not necessary to grow BHs. But BHs do not correlate with galaxy disks. And any correlations with disk-grown pseudobulges or halo dark matter are so weak as to imply no close coevolution. We suggest that there are four regimes of BH feedback. 1- Local, stochastic feeding of small BHs in mainly bulgeless galaxies involves too little energy to result in coevolution. 2- Global feeding in major, wet galaxy mergers grows giant BHs in short, quasar-like "AGN" events whose feedback does affect galaxies. This makes classical bulges and coreless-rotating ellipticals. 3- At the highest BH masses, maintenance-mode feedback into X-ray gas has the negative effect of helping to keep baryons locked up in hot gas. This happens in giant, core-nonrotating ellipticals. They inherit coevolution magic from smaller progenitors. 4- Independent of any feedback physics, the averaging that results from successive mergers helps to engineer tight BH correlations.

Title: Atomic Hydrogen in a Galactic Center Outflow
Authors: McClure-Griffiths, N. M.; Green, J. A.; Hill, A. S.; Lockman, F. J.; Dickey, J. M.; Gaensler, B. M.; Green, A. J.
Publication: eprint arXiv:1304.7538
Publication Date: 04/2013
Origin: ARXIV
Keywords: Astrophysics – Galaxy Astrophysics
Comment: Accepted for publication in Astrophysical Journal Letters
Bibliographic Code: 2013arXiv1304.7538M


We describe a population of small, high velocity, atomic hydrogen clouds, loops, and filaments found above and below the disk near the Galactic Center. The objects have a mean radius of 15 pc, velocity widths of $\sim 14$ km/s and are observed at $|z|$ heights up to 700 pc. The velocity distribution of the clouds shows no signature of Galactic rotation. We propose a scenario where the clouds are associated with an outflow from a central star-forming region at the Galactic Center. We discuss the clouds as entrained material traveling at $\sim 200$ km/s in a Galactic wind.

Title: Unidentified Infrared Emission bands: PAHs or MAONs?
Authors: Kwok, Sun; Zhang, Yong
Publication: eprint arXiv:1304.7629
Publication Date: 04/2013
Origin: ARXIV
Keywords: Astrophysics – Galaxy Astrophysics
Comment: 9 figures, accepted for publication in The Astrophysical Journal
Bibliographic Code: 2013arXiv1304.7629K


We suggest that the carrier of the unidentified infrared emission (UIE) bands is an amorphous carbonaceous solid with mixed aromatic/aliphatic structures, rather than free-flying polycyclic aromatic hydrocarbon (PAH) molecules. Through spectral fittings of the astronomical spectra of the UIE bands, we show that a significant amount of the energy is emitted by the aliphatic component, implying that aliphatic groups are an essential part of the chemical structure. Arguments in favor of an amorphous, solid-state structure rather than a gas-phase molecule as a carrier of the UIE are also presented.

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