## Friday, October 30, 2009

### Interesting Astrophysics: 26 Oct to 30 Oct

Galaxies and Starbursts

A New Empirical Method to Infer the Starburst History of the Universe from Local Galaxy Properties
Philip F. Hopkins, Lars Hernquist,
Comments: 21 pages, 8 figures, accepted to MNRAS

Constraining the initial mass function of stars in the Galactic Centre
Ulf Loeckmann, Holger Baumgardt, Pavel Kroupa,
Comments: MNRAS, accepted, 8 pages, 4 figures

HI Selected Galaxies in the Sloan Digital Sky Survey I: Optical Data
Andrew A. West, Diego A. Garcia-Appadoo, Julianne J. Dalcanton, Mike J. Disney, Constance M. Rockosi, Zeljko Ivezic, Misty C. Bentz, J. Brinkmann,
Comments: 14 pages, 8 Figures, accepted for publication in AJ. Complete tables will be available in the AJ electronic version and on the Vizier site

HI Selected Galaxies in the Sloan Digital Sky Survey II: The Colors of Gas-Rich Galaxies
Andrew A. West, Diego A. Garcia-Appadoo, Julianne J. Dalcanton, Mike J. Disney, Constance R. Rockosi, Zeljko Ivezic,
Comments: 12 pages, 16 figures, published in AJ (138, 796); replaced Figure 16 with higher resolution version
Journal-ref: West et al. 2009, AJ, 138, 796

Numerical Astrophysics

Adaptive Mesh Fluid Simulations on GPU
Peng Wang, Tom Abel, Ralf Kaehler,

CUDA & MPI, with what sounds like the ZEUS MHD scheme. Hardly surprising, but nice to see some effort going into exploring the use of GPU computing with hydro codes.

Stars, Supernovae and Planets

Evolution of supermassive stars as a pathway to black hole formation
Mitchell C. Begelman,
Comments: 10 pages, 5 figures, to appear in Monthly Notices of the Royal Astronomical Society

X-ray observations of classical novae. Theoretical implications
M. Hernanz, G. Sala,
Comments: 6 pages, review paper accepted for publication in Astronomische Nachrichten

The Nature and Nurture of Star Clusters
Bruce G. Elmegreen,
Comments: to be published in IAUS266: Star Clusters Basic Galactic Building Blocks Throughout Time And Space, eds. Richard de Grijs and Jacques Lepine, Cambridge University Press, 11 pages

Nuclear Star Clusters
Torsten Boeker,
Comments: invited talk at IAU Symp. 266 "Star Clusters: Galactic Building Blocks through Space and Time"

## Friday, October 23, 2009

### Interesting Astrophysics: Oct 12 to Oct 23

This edition of Interesting Astrophysics spans an even wide range of topics than normal, from C IV in the IGM (D'Odorico et al), X-ray emission from galaxies (Laird et al, Pietsch), a variety of supernova-related preprints, to AGN feedback/outflows and other topics I've not mentioned.

Galaxies and Starbursts

An Anisotropic Propagation Model for Galactic Cosmic Rays
Iris Gebauer, Wim de Boer,
Comments: 19 pages, 19 figures, submitted to A&amp;A

The rise of the C IV mass density at z<2.5
Valentina D'Odorico, Francesco Calura, Stefano Cristiani, Matteo Viel,
Comments: Paper accepted by MNRAS. The parameters of the C IV line fitting will be available in electronic format

The radial distribution of core-collapse supernovae in spiral host galaxies
A. A. Hakobyan, G. A. Mamon, A. R. Petrosian, D. Kunth, M. Turatto,
Comments: 10 pages, 6 figures, 5 tables. Astronomy &amp; Astrophysics, in press

On the X-ray properties of submm-selected galaxies
Elise S. Laird, Kirpal Nandra, Alexandra Pope, Douglas Scott,
Comments: 12 pages, 5 figures, accepted for publication in MNRAS

X-ray emission from optical novae in M 31
W. Pietsch,
Comments: 6 pages, 4 figures, accepted for publication in Aston.Nachr

Bars in Starbursts and AGNs -- A Quantitative Reexamination
Lei Hao, Shardha Jogee, Fabio D. Barazza, Irina Marinova, Juntai Shen,
Comments: 8 pages, 3 figures, to be published in "Galaxy Evolution: Emerging Insights and Future Challenges", ed. S. Jogee et al., Astron. Soc. Pacific, 2009

From their abstract: "We find that AGN and star-forming galaxies have similar optical bar fractions, 47% and 50%, respectively. Both bar fractions are higher than that in inactive galaxies (29%)."

Extragalactic CS survey
Comments: 17 pages, 16 figures, 3 tables, Accepted to ApJ

From the abstract: "We present a coherent and homogeneous multi-line study of the CS molecule in nearby (D$<$10Mpc) galaxies. We include, from the literature, all the available observations from the $J=1-0$ to the $J=7-6$ transitions towards NGC 253, NGC 1068, IC 342, Henize~2-10, M~82, the Antennae Galaxies and M~83."

Black Holes and AGN

Feeding and Feedback in nearby AGN from Integral Field Spectroscopy
Thaisa Storchi-Bergmann,
Comments: 4 pages, 2 figures, to appear in the proceedings of the conference "The Monster's Fiery Breath", eds. Sebastian Heinz and Eric Wilcots

From the abstract: "The ionized gas, on the other hand, traces the AGN feedback. Its
kinematics shows two components: (1) one originating in the plane, and
dominated by circular rotation; (2) another outflowing along the Narrow-Line
Region (NLR) whose flux distribution and kinematics frequently correlate with
structures seen in radio maps. Mass outflow rates along the NLR range from
10^-2 to 1 M_sun yr^-1, corresponding to 10-100 times the accretion rate to the
AGN, indicating that most of the NLR gas mass has been entrained from the
galaxy plane. The average kinetic power of the NLR outflows is ~10^-4 times the
bolometric luminosity.
"

AGN Feedback: Does it work?
Smita Mathur, Rebecca Stoll, Yair Krongold, Fabrizio Nicastro, Nancy Brickhouse, Martin Elvis,
Comments: to appear in proceedings of the conference "The Monster's Fiery Breath: Feedback in Galaxies, Groups, and Clusters", June 2009, Madison, WI, Eds. S. Heinz &amp; E. Wilcots

Interstellar Medium

PAH processing in interstellar shocks
E. R. Micelotta, A. P. Jones, A. G. G. M. Tielens,
Comments: 21 pages, 11 figures, accepted for publication in Astronomy and Astrophysics

VLT/FLAMES-ARGUS observations of stellar wind--ISM cloud interactions in NGC 6357
M.S. Westmoquette, J.D. Slavin, L.J. Smith, J.S. Gallagher III,
Comments: 9 pages, 5 figures (3 colour). Accepted for publication in MNRAS

Stars, Supernovae and Planets

The rebrightening of planetary nebulae through ISM interaction

C J Wareing,

Comments: Review paper accepted to PASA. 8 pages, 5 figures. High resolution images available from the author

Stellar Feedback in Molecular Clouds and its Influence on the Mass Function of Young Star Clusters
S. Michael Fall, Mark R. Krumholz, Christopher D. Matzner,
Comments: 5 pages, 2 figures, emulateapj format, submitted to ApJL

Typing Supernova Remnants Using X-ray Line Emission Morphologies
Laura A. Lopez, Enrico Ramirez-Ruiz, Carles Badenes, Daniela Huppenkothen, Tesla E. Jeltema, David A. Pooley,
Comments: 4 pages, 1 figure, accepted for publication in ApJL

Line-of-sight Shell Structure of the Cygnus Loop
Hiroyuki Uchida, Hiroshi Tsunemi, Satoru Katsuda, Masashi Kimura, Hiroko Kosugi, Hiroaki Takahashi,
Comments: 8 pages, 7 figures, accepted for publication in ApJ
Journal-ref: Astrophysical Journal 705 (2009) 1152-1159

Other

FISH: A 3D parallel MHD code for astrophysical applications
R. Kaeppeli, S. C. Whitehouse, S. Scheidegger, U.-L. Pen, M. Liebendoerfer,

Astrometry.net: Blind astrometric calibration of arbitrary astronomical images
Dustin Lang, David W. Hogg, Keir Mierle, Michael Blanton, Sam Roweis,

A very cool idea!

## Friday, October 09, 2009

### Interesting Astrophysics: 05 Oct to 09 Oct

A mixed bag of interesting preprints this week. Of note are local analogs of the Lyman Break Galaxies (Overzier et al), the radio-FIR correlation at high z (Lacki & Thompson), and a possible optical counterpart to an intermediate mass black hole candidate (Soria et al).

Galaxies and Starbursts

Local Lyman Break Galaxy Analogs: The Impact of Massive Star-forming Clumps on the Interstellar Medium and the Global Structure of Young, Forming Galaxies
R.A. Overzier, T.M. Heckman, C. Tremonti, L. Armus, A. Basu-Zych, T. Goncalves, R.M. Rich, D.C. Martin, A. Ptak, D. Schiminovich, H.C. Ford, B. Madore, M. Seibert,
Comments: The Astrophysical Journal, In Press (22 pages, 16 figures). For the full version with high-resolution colour figures, see: this http URL

Stationary models for the extra-planar gas in disc galaxies
F. Marinacci, F. Fraternali, L. Ciotti, C. Nipoti,
Comments: 14 pages, 7 figures, accepted for pubblication in MNRAS

A cloudy halo model.

The Physics of the FIR-Radio Correlation: II. Synchrotron Emission as a Star-Formation Tracer in High-Redshift Galaxies
Brian C. Lacki, Todd A. Thompson,

The fundamental gas depletion and stellar-mass buildup times of star forming galaxies
Jan Pflamm-Altenburg, Pavel Kroupa,
Comments: accepted for publication in ApJ

The WMAP haze from the Galactic Center region due to massive star explosions and a reduced cosmic ray scale height
Peter L. Biermann, Julia K. Becker, Gabriel Caceres, Athina Meli, Eun-Suk Seo, Todor Stanev,

Black Holes and AGN

The Activity of the Neighbours of AGN and Starburst Galaxies: Towards an evolutionary sequence of AGN activity
E.Koulouridis, M.Plionis, V.Chavushyan, D.Dultzin, Y.Krongold, I.Georgantopoulos, C.Goudis,
Comments: 50 pages, 5 figures, 41 spectra

Discovery of an optical counterpart to the hyperluminous X-ray source in ESO 243-49
Roberto Soria, George K. T. Hau, Alister W. Graham, Albert K. H. Kong, N. Paul M. Kuin, I-Hui Li, Ji-Feng Liu, Kinwah Wu,
Comments: 5 pages, submitted to MNRAS Letters. Contact R Soria for higher-resolution figures

Theoretical and Numerical Astrophysics, including Cosmology

Pressure Support vs. Thermal Broadening in the Lyman-alpha Forest II: Effects of the Equation of State on Transverse Structure
Molly S. Peeples, David H. Weinberg, Romeel Davé, Mark A. Fardal, Neal Katz,
Comments: 11 figures, submitted to MNRAS

Stars, Supernovae and Planets

Ionized Gas Towards Molecular Clumps: Physical Properties of Massive Star Forming Regions
Katharine G. Johnston, Debra S. Shepherd, James E. Aguirre, Miranda K. Dunham, Erik Rosolowsky, Kenneth Wood,
Comments: 67 pages, 16 figures, 8 tables, accepted for publication in ApJ

From their abstract: "For clumps with associated ionized gas, the combined mass of the ionizing massive stars is compared to the clump masses to provide an estimate of the instantaneous star formation efficiency. These values range from a few percent to 25%, and have an average of 7 +/- 8%. We also find a correlation between the clump mass and the mass of the ionizing massive stars within it, which is consistent with a power law. This result is comparable to the prediction of star formation by competitive accretion that a power law relationship exists between the mass of the most massive star in a cluster and the total mass of the remaining stars."

## Thursday, October 08, 2009

### HuffPo lunacy

The Huffington Post has a certain reputation for allowing (perhaps it would be more accurate to say promoting) quacks, vaccine denialists, conspiracy theorists and other superstitious wackery, but the example that follows is impressively moronic even by HuffPo standards.

As Tariq Malik at Space.com reports regarding NASA's LCROSS lunar impact (emphasis mine):

NASA's LCROSS mission will slam a spacecraft and an empty rocket stage into the moon's south pole Friday morning at 7:31 a.m. EDT (1131 GMT) in a search for water ice buried in the perpetual shadows of lunar craters.

Scientists are eagerly awaiting the LCROSS crashes and hope they'll provide a definitive answer on whether lunar water ice could be used to support future astronauts on the moon. But at least one person — novelist and screenwriter Amy Ephron — has spoken out against the \$79 million mission on her Huffington Post blog and launched a Twitter campaign ("helpsavethemoon") to save the moon from future onslaught.

"I'm not a big fan of explosions, anyway. In Iraq or Afghanistan or the South Pole of the Moon. But who does have a territorial prerogative there?" Ephron wrote. "Who has jurisdiction? Who has the right to say that it's okay to blow up a crater on the moon?"

Apparently, Mother Nature does. The moon is covered in craters, with new ones like those to be created by the LCROSS probes popping up all the time by meteorites that pummel the lunar surface.

"The image of this impact, what we're doing with the moon, is something that occurs naturally four times a month on the moon, whether we're there or not," LCROSS principal investigator Tony Colaprete told reporters Thursday.

I love Malik and Colaprete's understated but effectively utter refutation of Ephron's deliberately ignorant rant. Keep it up!

### New mega ring around Saturn discovered using Spitzer

Infrared observations using the Spitzer Space Telescope, published by Verbiscer et al (2009, Nature), have revealed the largest known ring around Saturn, an annulus of very tenuous material extending between 6 million and 18 million kilometers from Saturn, and tilted by 27 degree from the plane of the traditional rings (which only extend out to ~240,000 km).

The material in the new ring comes from the battered and cratered moon Phoebe. Of more interest, this new dust ring explains why the leading side of Iapetus is so much darker than the rest of it - the dark front surface of Iapetus is material from the ring swept up by Iapetus as it orbits at the inner edge of the new ring.

In truth a link between the dark front of Iapetus and Phoebe has been suspected before now, as the composition of the dark material is very similar to that of Phoebe based on near IR spectroscopy with Cassini. What the Spitzer observations reveal is the presence of the dust ring and hence the mechanism of material transfer from Phoebe to Iapetus.

Although the ring is physically huge, with a volume of ~5e21 km^3 (this is my BOTE calculation. As far as I can tell Verbiscer et al do not quote a volume), it is incredibly tenuous, and if all the material within it were collected back into one place it would possibly only occupy ~ 1 km^3 of rock, i.e. the volume of a crater on Phoebe.

The other interesting thing is that the material migrates inwards under the influence of radiation pressure. From Verbiscer et al:

On long timescales, collisions and inward transport become important. Collision with Phoebe, the dominant loss mechanism for particles larger than several centimetres in size, takes on the order of 1010 years. Re-radiation of absorbed sunlight exerts an asymmetric force on dust grains, causing them to spiral in towards Saturn with a characteristic timescale of 1.5 105rg years where rg is the particle radius in micrometres. This force brings all centimetre-sized and smaller material to Iapetus and Titan unless mutual particle collisions occur first. The rate of mutual collisions depends on the size distribution of the ring particles and optical depth; if the ring were comprised entirely of 10 m grains, then the collisional timescale would be tens of millions of years, which is comparable to the inward drag timescale. Most material from 10 m to centimetres in size ultimately hits Iapetus, with smaller percentages striking Hyperion and Titan3.

References:

Verbiscer, A., Skrutskie, M., & Hamilton, D. (2009). Saturn's largest ring Nature DOI: 10.1038/nature08515

BBC article published by Jonathan Amos. 2009/10/08 (the source of the nice graphic shown above).

Spitzer press release, 2009/10/06.

## Friday, October 02, 2009

### Interesting Astrophysics: Sep 28 to Oct 02

A mixed bag of preprints this week. From my personal perspective I'd say the Marchili et al paper on M82' SN2008iz and Acero et al's paper on a gamma ray detection of NGC 253 are the most interesting.

Galaxies and Starbursts

The radio lightcurve of SN 2008iz in M82 revealed by Urumqi observations
N. Marchili, I. Marti-Vidal, A. Brunthaler, T.P. Krichbaum, P. Mueller, X. Liu, H.-G. Song, U. Bach, R. Beswick, J.A. Zensus,
Comments: 7 pages, 3 figures. Accepted for publication in A &amp; A

Detection of Gamma Rays From a Starburst Galaxy
The HESS Collaboration: F. Acero, et al,
Comments: 24 pages, 8 figures, published in Science Express, see: this http URL

Reported H.E.S.S. gamma ray detection of NGC 253, F()>220 GeV) = [5.5 +/- 1.0(stat) +/- 2.8 (sys)] times 10-13 cm-2 s-1. Much of the interpretation is done under the assumption that all the activity is due to the starburst, and NOT related to any AGN, which I'm not personally sure is a robust assumption. Still its an interesting mini-paper.

Star Formation Histories within the Antennae Galaxies (Arp 244)
Hong-Xin Zhang, Yu Gao, Xu Kong,
Comments: 13 pages, 7 figures, accepted by MNRAS

How ubiquitous are massive starbursts in interacting galaxies?
P. Di Matteo, F. Bournaud, M. Martig, F. Combes, A.-L. Melchior, B. Semelin,
Comments: 4 pages, Proceedings of the conference "Galaxies in isolation: exploring Nature vs Nurture" (May 2009, Granada, Spain)

Comparison of H-alpha and UV Star Formation Rates in the Local Volume: Systematic Discrepancies for Dwarf Galaxies
Janice C. Lee, Armando Gil de Paz, Christy Tremonti, Robert C. Kennicutt Jr., Samir Salim, Matthew Bothwell, Daniela Calzetti, Julianne Dalcanton, Daniel Dale, Chad Engelbracht, Jose G. Funes S.J., Benjamin Johnson, Shoko Sakai, Evan Skillman, Liese van Zee, Fabian Walter, Daniel Weisz,
Comments: 29 pages, 10 figures, 2 tables, accepted for publication in ApJ

The Far-Infrared--Radio Correlation at High Redshifts: Physical Considerations and Prospects for the Square Kilometer Array
Eric J. Murphy,
Comments: 16 pages, 8 figures, accepted for publication in ApJ

What stellar populations can tell us about the evolution of the mass-metallicity relation in SDSS galaxies
N. Vale Asari, G. Stasinska, R. Cid Fernandes, J. M. Gomes, M. Schlickmann, A. Mateus, W. Schoenell,
Comments: To appear in the proceedings of IAU symposium 262, 'Stellar Populations - Planning for the Next Decade'

From their abstract: "Our results suggest that the M-Z relation for galaxies with present-day stellar masses down to 10^10 solar masses is mainly driven by the star formation history and not by inflows or outflows." This strikes me as a bit odd for a major conclusion, as pretty much everyone agrees that M-Z is dominated by the SF history... the real argument if M-yeff, and the trends suggestive of outflow really kick in for galaxies *below* 10^10.5 solar masses.

Theoretical Cosmology

Can galaxy outflows and re-accretion produce the downsizing in specific star formation rate of late-type galaxies?

C. Firmani, V. Avila-Reese, A. Rodriguez-Puebla,

The physics driving the cosmic star formation history
Joop Schaye, Claudio Dalla Vecchia, C. M. Booth, Robert P. C. Wiersma, Tom Theuns, Marcel R. Haas, Serena Bertone, Alan R. Duffy, I. G. McCarthy, Freeke van de Voort,
Comments: Submitted to MNRAS, 27 pages and 18 figures

Numerical Astrophysics

A new radiative cooling curve based on an up to date plasma emission code
K.M. Schure, D. Kosenko, J.S. Kaastra, R. Keppens, J. Vink,
Comments: 11 pages, 6 figures. Accepted for publication in A&amp;A. Tables in text format online available at this http URL

Collisional ionisation equilibrium cooling, valid above 104 K.. Seems pretty straightforward.

Numerical Implementation of Streaming Down the Gradient: Application to Fluid Modeling of Cosmic Rays
Prateek Sharma, Phillip Colella, Daniel F. Martin,
Comments: submitted to SIAM J. of Scient. Comp.; 15 pages, 9 figs.; comments welcome

Stars, Supernovae and Planets

Stellar models: firm evidence, open questions and future developments
Santi Cassisi,
Comments: 10 pages, 3 figures, Keynote review talk at the IAU Symp. 262 "Stellar Populations - Planning the Next Decade" of the XXVIIth IAU General Assembly held in Rio de Janeiro (Brazil), Proceeding eds. G. Bruzual &amp; S. Charlot

Chandra observation of Cepheus A: The diffuse emission of HH 168 resolved
P. C. Schneider, H. M. Guenther, J. H. M. M. Schmitt,
Comments: 8 pages, 5 figures, accepted for publication in A&A

Core collapse supernovae and starbursts
Miguel A. Perez-Torres,
Comments: Proceedings of the 8th international e-VLBI Workshop, accepted for publication, 6 pages, 1 figure,

## Thursday, October 01, 2009

### Brian Switek reviews the Templeton Foundation's "Test of Faith" DVD series

Brian Switek has a characteristically thoughtful review of the Templeton Foundation's DVD miniseries "Test of Faith" on his blog. As Brian is not one of those evil "divisive" (or worse: "uncivil") atheists like Dawkins, Coyne or PZ Myers I'd hope that his critique is not dismissed out of hand by pro-religion accommodationists.

Unfortunately for an organization that claims to represent a serious, sober and moderate vision of (some form of) religion and science not in being in conflict, the DVDs engage in much the same sort of God-of-the-gaps teleology and straw-man argumentation that creationists normally engage in.

Nor does the Templeton Foundation's vision of religion sound particularly deist or ecumenical. Brian writes:

I would not have been so aggravated with the program if it presented scientists who said something akin to "I am a Christian/Muslim/Buddhist/Pastafarian/&c. I believe [insert belief system here] on the basis of faith, and I feel what I have come to understand about the nature of the universe is consistent with the faith I practice. Rather than make nature conform to my beliefs, however, I would rather understand the world as it is. If it turns out to be inconsistent with my faith then I will have to question what I believe." I could at least respect that. Instead the Test of Faith series trots out scientist after scientist who believe that they have some special glimmer or proof of God in nature; it is going at the whole thing backwards. The impression the series gives is that the natural world justifies and supports a particular religion, Christianity, rather than stating that some liberal forms of that religion could accept the science of evolution. (Whether evolution is reconcilable with religion depends on what brand religion we're talking about.)
And people wonder why many scientists have little or no respect for the Templeton Foundation?

PS: The 'physicist Katherine Blundell [who] says that there are "truths" in the universe that science does not detect' (*) mentioned is most probably the Oxford astronomer Katherine Blundell, as she is associated with some organization called The Faraday Institute For Science and Religion.

* Oh really. How do you know?