Wednesday, May 25, 2011, 3:40 PM - 4:30 PM

Wednesday, May 25, 2011, 4:30 PM - 6:00 PM

317

AGN, Mergers, and Jets

Oral Session

America North

317.01

4:30 PM - 4:40 PM

Using high-resolution HST/WFC3 imaging in the J and H bands, we have examined the rest-frame optical morphologies and colors of X-ray selected AGN hosts at z~2 for the first time. This imaging was taken as part of the Cosmic Assembly Near-IR Deep Extragalactic Legacy Survey (CANDELS), which aims to document the evolution of galaxies and black holes at z > 1.5. I will show that from visual classifications we have determined that AGN hosts do not exhibit merger or interaction signatures more often than non-active galaxies of similar mass at this redshift. We have also used Galfit to determine the morphological breakup of these galaxies and find that a high fraction of the AGN are located in disk-like systems. Our results suggest that the bulk of the X-ray luminous AGN population at z~2 could not have been triggered by a major merger event in the recent past. I will compare the observed properties of the AGN hosts to what is predicted from semi-analytic cosmological models which incorporate a prescription for merger-triggered, self-regulated black hole growth and discuss the implications for AGN feedback models.

317.02

Space Densities Of AGN And The FR Dichotomy

Melanie Gendre¹, J. V. Wall², P. N. Best^3
1JBCA, United Kingdom, ²UBC, Canada, ³ROE, United Kingdom.

4:40 PM - 4:50 PM

Extended double-lobe radio sources can be morphologically classified into two groups: Fanaroff-Riley (FR) type I sources have the highest surface brightness along the jets near the core and FR type II sources show the highest surface brightness at the lobe extremities, as well as more collimated jets. This work focuses on a comparison of the space densities of FRI and FRII sources at different epochs, with a particular focus on FRI sources. The Combined NVSS-FIRST Galaxy catalogue (CoNFIG), a sample of radio sources at 1.4 GHz, includes VLA observations, FRI/FRII morphology classifications, optical identifications and redshift estimates. The final catalogue consists of 858 sources over 4 samples (CoNFIG-1, 2, 3 and 4 with flux density limits of S_1.4GHz = 1.3, 0.8, 0.2 and 0.05 Jy respectively). It is 95.7% complete in radio morphology classification and 74.3% of the sources have redshift data. Combining CoNFIG with complementary samples, the distribution and cosmic evolution of FRI and FRII sources are investigated. It is found that FRI sources undergo mild evolution and that, at the same radio luminosity, FRI and FRII sources show similar space density enhancements in various redshift ranges, implying a common mechanism powering the luminosity-dependent evolution. This improved understanding of radio galaxy evolution will also give better insight into the the physics of AGN and their role in galaxy formation.

317.03

Large scale Extragalactic Jets In The Chandra Era

Francesco Massaro¹, D. Harris¹, C. Cheung^2
1Smithsonian Astrophysical Observatory, ²National Radio Astronomy Observatory.

4:50 PM - 5:00 PM

We report initial results from a systematic investigation of the properties of large-scale AGN jets detected in X-rays. We have uniformly analyzed archival Chandra data for more than 90 such sources and measure fluxes in three X-ray bands to estimate spectra. We discuss the sample, the reduction methods, and present first results for the ratio of X-ray to radio flux and the spectral analysis for jet knots and hotspots. Utilizing archival VLA and MERLIN data, we examine the X-ray and radio properties for the jet knots and hotspots in the sample which includes quasars and low- and high-power (FR1 and FR2) radio galaxies. As two different processes have been proposed for the X-ray emission mechanism -- synchrotron and inverse Compton -- we discuss on a possible new classification scheme for extragalactic jets based on our data. From our comparison of their radio-to-X-ray properties, several aspects on their

317.04

5:00 PM - 5:10 PM

Radio loud active galactic nuclei are on average 1000 times brighter in the radio band than radio quiet ones. We investigate whether this radio loud/quiet dichotomy can be due to differences in the spin of central black holes (BHs) that power the radio emitting jets. We construct steady state axisymmetric numerical models for a wide range of BH spin, a. We assume that the magnetic flux that threads the BH is held constant. For a BH surrounded by a thin accretion disk, we find that the conventional expression for BH power, P ~ a^2, is accurate to within a factor of a few. We conclude that in this scenario differences in spin can account for power variations of at most a few tens. However, if the disk is thick, the power variation becomes much steeper, P ~ a^4 or even ~a^6. Power variations of 1000 are then possible for realistic BH spin distributions. We derive an analytic solution that accurately reproduces the steeper scaling of jet power with spin.

318

Dust and Star Formation

Oral Session

America Central

318.01

4:30 PM - 4:40 PM

We report spectroscopic detection of carbon monoxide at 4.5 micron fundamental band from the young supernova remnant Cassiopeia A (Cas A). AKARI Infrared Camera (IRC) observations were made towards 4 positions where narrow-filter CO image at 2.29 micron infers plausible detection of CO molecules. Our IRC spectroscopy unambiguously revealed broad features of CO fundamental bands. The CO emission is detected from all of four positions which include northern shell and Minkowski knot and central unshocked ejecta. The spectra show two main peaks, but peaks vary position to position. We can reproduce the observed emission with optically thin CO emission at temperatures between 1500 and 2500 K and at radial velocities of -2000 km/s. We will present comparison of CO in Cas A with that detected in supernovae. Our observations address importance of molecule formation and Type II supernovae are indeed factories of molecules in early Universe. We will discuss CO formation processes and mass of CO, degree of CO destruction in ejecta, implication of mixing, evolution of carbon dust, molecule and dust formation in early Universe. Future SOFIA FLITECAM and FORCAST grism instruments cover near- and mid-infrared wavelengths with a high resolution spectroscopy and will allow us to advance our understanding of molecule and dust evolution in galaxies and the Milky Way.

318.02

4:40 PM - 4:50 PM

The role magnetic fields play in star formation is not well understood, and it is possible that magnetic fields may play a critical role. Polarimetry, by tracing the dust grains aligned with the magnetic field, can probe the magnetic field in the clouds where star formation is occurring. Currently, the details of the process that aligns dust grains are still unknown. An understanding of the alignment mechanism is necessary to interpret polarization maps as potential tracers of the Galactic magnetic field. We present results of a study of near-infrared polarimetry of two large molecular clouds using data from the Galactic Plane Infrared Polarization Survey (GPIPS). GPIPS is a 76 sq. degree survey of the Galactic plane that uses the Mimir instrument on the 1.8m Perkins telescope outside Flagstaff, AZ. Recent evidence suggests that radiative torques (RATs) may be the dominant alignment mechanism in molecular clouds. If true, this would mean that the largest dust grains within dense regions of molecular clouds, the regions where the first stages of star formation occur, could be aligned and tracing the local magnetic field. By seeing how percentage polarization changes with increasing depth into dense regions of molecular clouds, we are able to test the predictions of the RATs theory. We also gain valuable insight about how deeply into clouds the magnetic field can be traced and also learn about the grain size distributions there. This work is partially supported by NSF AST 09-07790.

318.03

Recalibrating SFD Using SDSS Spectroscopy And Photometry

Eddie Schlafly¹, D. P. Finkbeiner^1
1Harvard.

4:50 PM - 5:00 PM

We use new measurements of reddening using SDSS photometry and spectroscopy to test the SFD dust map. We find that both the photometric and spectroscopic technique agree on a common SFD calibration that is different from the original SFD calibration by 13%. We find additionally that a Fitzpatrick 1999 reddening law provides a good fit to the reddening law derived from these techniques, while CCM and O'Donnell reddening laws are disfavored.

318.04

5:00 PM - 5:10 PM

Infrared observations are uniquely able to observe the astrophysical processes deep within dusty regions and to provide key information on the characteristics of the dust itself. This information is critical for learning the role of dust in gas physics, for exploring how dust processing occurs, and for understanding the formation and destruction mechanisms of dust grains. Though relevant astronomical and ground-based observations already exist, the properties of dust at these long wavelengths are poorly known, and since observed spectral features of dust are used to infer characteristics of the surrounding neighborhood, these large uncertainties lead to ambiguity in interpretation. The OPASI-T program addresses the need for high fidelity optical characterization data in the far and mid infrared, aiming at the creation of a unique library of the optical properties of metal-enriched silicate condensates. Such database will cover a wide wavelength range connecting numerical data with laboratory and astronomical spectra in the mid infrared, while providing new data in the unexplored far-infrared and millimeter regime. Both new and established experiments are used to measure the transmission and reflection properties of amorphous silicates across the infrared, which are then analyzed by way of numerical methods in order to determine the variations of their optical constants and complex dielectric function as a function of wavelength. I will present room-temperature measurements of SiO in a KBr matrix from 5 to 25 μm and its optical properties as derived from a least-squares nonlinear fit applied to a mixed approach coupling the Maxwell-Garnett theory, the Lorentz dispersive model for mixtures, and the averaged equation for transmission. This material is based upon work supported by NASA through the ROSES/APRA program. This research was supported by an appointment (Cataldo) at the Goddard Space Flight Center administered by Universities Space Research Association through a contract with NASA.

318.05

5:10 PM - 5:20 PM

We combine new accurate calculations, asymptotic relations, and available experimental data to construct an H- photodetachment cross section reliable for a large range of photon energies. In particular, account is taken of the series of auto-detaching shape and Feshbach resonances between

318.06

5:20 PM - 5:30 PM

Identifying and characterizing the mass outflows associated with low-mass protostars is challenging since the outflowing gas is deeply embedded and often characterized by velocities comparable to the cloud turbulence. In order to investigate the evolution of such outflows, we use self-gravitating, radiation-hydrodynamic simulations performed with the Adaptive Mesh Refinement code, Orion. We construct synthetic observations in 12CO in order to compare with recent observations and assess the effects of beam resolution and outflow orientation on inferred outflow properties. We find that the interaction between the outflows and the turbulent core envelopes produces significant asymmetry. In addition, the opening angle broadening with time in both the simulations and CO synthetic observations is similar to that of observed outflows.

318.07

The Enigmatic Dense Core L1451-mm: A First Hydrostatic Core Candidate

Jaime E. Pineda¹, A. A. Goodman², H. G. Arce³, S. Schnee⁴, T. Bourke², J. Foster⁵, T. Robitaille², J. Tanner³, J. Kauffmann⁶, M. Tafalla⁷, P. Caselli⁸, G. Anglada^9
1University of Manchester, United Kingdom, ²Harvard University, ³Yale University, ⁴NRAO, ⁵Boston University, ⁶JPL, ⁷OAN, Spain, ⁸University of Leeds, United Kingdom, ⁹IAC-CSIC, Spain.

5:30 PM - 5:40 PM

We present the detection of a dust continuum source at 93GHz (CARMA) and 230GHz (SMA), and 12CO(2-1) emission (SMA) towards the L1451-mm dense core located in the Perseus Cloud. These detections suggest a compact object and an outflow where no point source is detected using Spitzer. An upper limit for the dense core bolometric luminosity of 0.07Lsun is obtained. We simultaneously model the broadband SED and the continuum visibilities, and the modeling confirms that a central source of heating is needed to explain the observations. It also shows that the data can be well fitted by a dense core with a YSO and disk, or by a dense core with a central First Hydrostatic Core (FHSC). Unfortunately, we are not able to rule out any of these two models, which produce similar fits. We also detect 12CO(2-1) emission with red- and blue-shifted emission suggesting the presence of a slow and poorly collimated outflow, in opposition to what is usually found towards young objects but in agreement with prediction from simulations of a FHSC. This presents the best candidate, so far, for a FHSC, an object that has been identified in simulations of collapsing dense cores. Whatever the true nature of the central object in L1451-mm, this core presents an excellent laboratory to study the earliest phases of star formation.

318.08

EVLA Continuum Observations of Massive Protostars

Peter Hofner^1
1New Mexico Tech..

5:40 PM - 5:50 PM

The study of the formation of massive stars throughout the galaxy was enabled by sensitive radiointerferometers likethe VLA, which were instrumental in defining ultra/hypercompact HII region as an early manifestation of newly formed massive stars. At yet younger evolutionary phases we expect

319

Galaxy Clusters

Oral Session

America South

319.01

4:30 PM - 4:40 PM

We combine the CIRS (Cluster Infall Regions in SDSS) sample of 72 clusters at z<0.1 with the HeCS (Hectospec Cluster Survey) sample of 74 clusters in the redshift range 0.1-0.3. Both samples are X-ray flux limited. HeCS contains over 20,000 new redshifts obtained with Hectospec on the MMT. We apply the caustic technique to this full sample of 148 clusters to measure M200 directly and to derive the NFW concentration from the fits of the mass profile to each cluster. We derive the correlation between concentration and mass and its spread at fixed mass and compare these measurements with the expected results from numerical simulations. We also tested the conjecture from some weak lensing studies that cluster concentrations substantially exceed model predictions.

319.02

4:40 PM - 4:50 PM

The cluster Abell 781D offers a unique challenge for weak lensing mass measurements. It is situated in the Deep Lens Survey (DLS) field F2 adjacent to 3 other clusters coincident on the sky that make up Abell 781. One of these clusters (Abell 781A) has a nearly identical redshift, X-ray and dynamical mass to Abell 781D. However, Abell 781A is detected with the expected significance in the weak lensing reconstruction, while the significance of the signal at the location of Abell 781D is conspicuously low. We use imaging from OPTIC on WIYN and archival Suprime imaging of this region to reanalyze the weak lensing mass of this cluster. We use these analyses to rule out systematics from the PSF characterization in the DLS map and to show that the source of the discrepancy between the weak lensing derived mass and the masses derived using other proxies is a real effect that requires careful characterization before weak lensing calibration of mass-observable relationships can be fully trusted.

319.03

X-ray Mass Proxies From Hydrodynamic Simulations Of Galaxy Clusters

Elena Rasia^1
1University of Michigan.

4:50 PM - 5:00 PM

Using extended sets of cosmological hydro-dynamical simulations of galaxy clusters, we present a detailed study of scaling relations between the total mass and three mass proxies based on X-ray observable quantities: temperature, gas mass, and the product of the two, YX. Our analysis is based on 140 clusters (M_vir > 5e13 Msun/h) with 30 objects having mass larger than 1e15 Msun/h at redshift 0. The large statistics is used to quantify the robustness of the scaling relations, to determine their redshift evolution, and to calibrate their intrinsic scatter and its distribution. We further use another set of 18 objects simulated with 7 different recipes for the physics of the gas to test the robustness of mass proxies against plasma physics.

5:00 PM - 5:10 PM

We present a weak lensing analysis of the rare major merger cluster Abell 2465 at z=0.245. Using deep CFHT i-band imaging we reconstruct the mass distribution, resolving the structure in this double cluster. We find the lensing cluster mass estimates to be consistent with the spectroscopic virial mass estimates of the two cluster components with masses of approximately 4 x 10^{14} solar masses. We also compare our lensing reconstruction to the distribution of hot X-ray gas in the region. Optical properties of the cluster are described in Wegner (2011; arXiv:1101.1451).

319.05

5:10 PM - 5:20 PM

Nominally designed to locate high-redshift galaxies magnified by 44 massive foreground clusters, the ``Herschel Lensing Survey'' (HLS; PI: Egami) also provides deep 5-band, far-infrared (FIR) imaging of the galaxies contained within those clusters. For sources at these redshifts (z~0.2-0.4), Herschel photometry spans the peak of the dust component, allowing us to constrain the dust properties, measure total infrared luminosity and hence derive obscured star formation rate. Although a large fraction of galaxies in massive clusters are quiescent early-types and therefore remain undetected by Herschel, the far-infrared highlights regions of activity within the system. The FIR effectively probes the transitional phases of cluster galaxy evolution, exposing starburst mechanisms such as tidal interactions and mergers, as well as the remnants of the as-yet un-quenched in-fall population.

320

Pulsars and Neutron Stars

Oral Session

Staffordshire

320.01

Violation of the Inverse Square Law deduced from a Maximum-Likelihood Analysis of Observational Data on Fluxes and Distances of Radio Pulsars

John Singleton¹, J. Middleditch², A. Schmidt², P. Sengupta³, H. Ardavan^4
1National High Magnetic Field Laboratory, ²Los Alamos National Laboratory, ³Nanyang Technological University, Singapore, ⁴Cambridge University, United Kingdom.

4:30 PM - 4:40 PM

Staffordshire

We have analyzed pulsar fluxes at 1400 MHz (S₁₄₀₀) and distances (d) extracted from the Parkes Multi-beam Survey using the Maximum Likelihood and other statistical methods. The only assumptions of our analyses are that distribution of pulsar luminosities is distance-independent and that the flux varies as 1/dⁿ, with n an adjustable parameter. If pulsars with singly-peaked pulse profiles, and f₀w₅₀ < 0.03, where f₀ is the rotational frequency in Hz and w₅₀ is the 50% width in seconds, are selected (comprising some 40% of the Parkes database), their flux is found to diminish with distance as 1/d, rather than as the conventional inverse square law. This result is extremely robust, with the error measure for n = 1 being some six orders of magnitude better than that for n = 2. By contrast, when applied to other astronomical objects, the same analysis techniques return the value n = 2 expected for the inverse-square law. Our result supports a model for pulsars based on the emission of radiation by superluminal polarization currents that has also successfully explained the frequency spectrum of the Crab and 8 other pulsars over 16 orders of magnitude of frequency. This work is supported by US Department of Energy LDRD program.

320.02

Fitting Of Fermi Lat Observations Of Gamma-ray Emitting Pulsars To The Frequency Spectrum Of A Faster-than-light Source

Andrea C. Schmidt¹, J. Singleton², H. Ardavan³, J. Middleditch^4
1LANL/UNM, ²MPA-NHMFL, ³University of Cambridge, United Kingdom, ⁴LANL.

4:40 PM - 4:50 PM

Staffordshire

Recently, we compared multiwavelength observations of nine pulsars with the radiation generated by a polarization current that travels faster than light in a circular orbit, the so-called Superluminal Model for Pulsars (SMP). We found that this single emission process accounts quantitatively for the spectrum of each pulsar over 16-18 orders of magnitude of frequency with minimal adjustable parameters. Here we apply the SMP to observations of gamma-ray emitting pulsars by the Fermi Large Area Telescope (LAT) combined with radio-frequency observations from other instruments.

The SMP invokes emission by superluminal (faster than light) polarization currents. In this context, polarization P results from displacement of positive and negative charges in opposite directions; a polarization current occurs when a polarized region moves or changes with time t. If a polarization current oscillates or accelerates, it will emit electromagnetic radiation, just as a current of electrons does. However, unlike electrons, which possess rest mass and are therefore limited to subluminal speeds, polarization currents are moving patterns that may travel arbitrarily fast.
While the overall form of the fitted spectra is given by the superluminal nature of the source, their fine structure is influenced by the detailed behavior of the pulsar atmosphere. The two most important parameters are ω, the pulsar's rotational frequency, and Ω, a resonant frequency of the atmosphere around where the emission occurs. It is natural to ascribe the latter to the plasma frequency. All of the pulsars investigated exhibit one further feature; an enhancement of the emission at higher frequencies, which can be attributed to cyclotron resonance of the electrons in the pulsar’s magnetic field. With parameters extracted from the broadband fits, we have calculated values for the number density of electrons and the magnetic field B at the emitting region and derived some systematic properties of these pulsars' plasma atmospheres.

320.03

Discovery of Hottest Superfluid and Superconductor in the Universe

Wynn C. G. Ho¹, P. S. Shternin², D. G. Yakovlev², C. O. Heinke³, D. J. Patnaude^4
1University of Southampton, United Kingdom, ²Ioffe Physical Technical Institute, Russian Federation, ³University of Alberta, Canada, ⁴Smithsonian Astrophysical Observatory.

4:50 PM - 5:00 PM

Staffordshire

The Cassiopeia A supernova remnant contains a young (about 330-yr-old) neutron star which has a carbon atmosphere and shows a notable decline of the surface temperature. We report a new Chandra observation which confirms the previously reported decline rate. The decline is naturally explained by superconductivity and superfluidity of the protons and neutrons in the stellar core. The protons became superconducting early in the life of the neutron star and suppressed the early cooling rate; thus the neutron star remained hot before the (recent) onset of neutron superfluidity. Once the neutrons became superfluid, the Cooper pair formation process produces a splash of neutrino emission, which accelerates the cooling and results in the observed rapid decline of surface temperature. This scenario puts stringent constraints on poorly-known properties of neutron star cores: on the density dependence of the temperature for the transition to neutron superfluidity, on the early onset of proton superfluidity/superconductivity, and on the reduction factor of the Cooper pair formation process by collective effects in superfluid matter. This represents the first direct evidence for nucleon superfluidity in neutron star cores.

320.04D

Estimating the Gamma-ray Pulsar Population with the Fermi-LAT Blind Search Sensitivity

Michael Dormody¹, Fermi-LAT Collaboration
¹UCSC.

5:00 PM - 5:20 PM

Staffordshire

The number of gamma-ray pulsars discovered in blind frequency searches of Fermi-LAT photon data raises the question of how many pulsars are in our Galaxy, as well as the pulsars' underlying energy and spatial distribution. By using a Galactic pulsar distribution (Faucher-Giguere et al. 2006) and assuming a pulse profile and spectrum similar to those previously detected in blind searches, along with an understanding of the sensitivity of the instrument to blind searches, we can estimate the underlying birth characteristics of pulsars. We present results on this detailed pulsar population study, including estimations of population size and initial spin-down energy distribution.

320.05

Searching For The First "Radio-Quiet" Gamma-ray Emitting Millisecond Pulsar

Albert K.H. Kong¹, R. H. H. Huang¹, P. H. T. Tam¹, K. S. Cheng², J. Takata², C. Y. Hui^3
1National Tsing Hua University, Taiwan, ²University of Hong Kong, Hong Kong, ³Chungnam National University, Korea, Republic of.

5:20 PM - 5:30 PM

Staffordshire

We report multi-wavelength observations of an unidentified Fermi object in the first-year Fermi catalog. The Fermi source has a candidate X-ray counterpart from Swift and Chandra data. We also identify a possible optical counterpart using the X-ray data. Its X-ray and gamma-ray properties are consistent with known gamma-ray millisecond pulsars. There is a possible X-ray modulation while optical/UV observations indicate that the system is likely in a low-mass X-ray binary system. No known radio source is associated with the proposed counterpart and we suggest that the source is the first "radio-quiet" gamma-ray emitting millisecond pulsar in a low-mass X-ray binary currently in quiescence. This work is supported by the National Science Council of Taiwan.

320.06

On The Cooling Tails Of Thermonuclear X-ray Bursts: News From Terzan 5

Manuel Linares¹, D. Chakrabarty¹, M. van der Klis^2
1MIT, ²University of Amsterdam, Netherlands.

5:30 PM - 5:40 PM

Staffordshire

The neutron star transient and 11 Hz X-ray pulsar IGR J17480-2446, recently discovered in the globular cluster Terzan 5, showed unprecedented bursting activity during its 2010 October-November outburst. We analyzed all X-ray bursts detected with the Rossi X-ray Timing Explorer and find strong evidence that they all have a thermonuclear origin, despite the fact that many do not show the canonical spectral softening along the decay imprinted on type I X-ray bursts by the cooling of the neutron star photosphere. We show that the persistent-to-burst power ratio is fully consistent with the accretion-to-thermonuclear efficiency ratio along the whole outburst, as is typical for type I X-ray bursts. The burst energy, peak luminosity and daily-averaged spectral profiles all evolve smoothly throughout the outburst, in parallel with the persistent (non-burst) luminosity. We also find that the peak burst to persistent luminosity ratio determines whether or not cooling is present in the bursts from IGR J17480-2446, and argue that the apparent lack of cooling is due to the ``non-cooling'' bursts having both a lower peak temperature and a higher non-burst (persistent) emission. We conclude that the detection of cooling along the decay is a sufficient, but not a necessary condition to identify an X-ray burst as thermonuclear. Finally, we compare these findings with X-ray bursts from other rapidly accreting neutron stars.

320.07

Pulsar Timing Noise: Magnetospheric State Switching or Free Precession?

Ian Jones^1
1University of Southampton, United Kingdom.

5:40 PM - 5:50 PM

Staffordshire

Recent radio pulsar observations have demonstrated two interesting phenomena. In some pulsars, smooth variations have been observed in spin-down rate and pulse profile. A precessional interpretation was initially suggested to account for this. In other pulsars, very sharp switches have been observed between different pulse profiles. In the case of at least one pulsar (PSR B1931+24), there is also a sharp change in spin-down rate. This has led to a new model of pulsar variability, based on changes in the magnetosphere rather than on precession. In this talk I will discuss whether or not these two models, precession and magnetospheric state switching, can be reconciled, and examine whether or not the precession hypothesis is still a plausible one in accounting for the smoother timing variations seen in many pulsars.

320.08

Fermi/Gamma-ray Burst Monitor Analysis of SGR J1550-5418 Bursts During an Extreme Outburst in January 2009

Alexander Jonathan Van Der Horst¹, C. Kouveliotou², Y. Kaneko³, E. Gogus³, N. Gorgone⁴, GBM Magnetar Team
¹Universities Space Research Association, ²NASA/MSFC, ³Sabanci University, Turkey, ⁴Connecticut College.

5:50 PM - 6:00 PM

Staffordshire

In 2008 October, the Soft Gamma Repeater (SGR) J1550-5418 entered a burst active period that lasted one week. On 2009 January 22, the source entered a second, extremely active period, which lasted for one month, and was followed by a third, small episode in 2009 March. The highest number of bursts from the SGR (~450) was observed on January 22 with the Fermi/Gamma-ray Burst Monitor (GBM). The combination of the unique GBM temporal and spectral capabilities has enabled us to study spectra of most of these SGR bursts in great detail. We present here the results of our time integrated spectral and temporal analysis of all the bursts observed with GBM during the source's active period in January 2009. Further, we compare the properties of these bursts with bursts observed from other SGR sources during extreme activations.

321

Molecular Clouds, HII Regions, Interstellar Medium

Oral Session

St. George CD

321.01

Galactic Plane Infrared Polarization Survey - First Data Release

Dan P. Clemens¹, A. Pinnick¹, M. Pavel¹, J. Moreau¹, R. Marchwinski¹, M. Bartlett¹, B. Taylor^1
1Boston Univ..

4:30 PM - 4:40 PM

St. George CD

We announce the initial public release of data products from the ongoing Galactic Plane Infrared Polarization Survey (GPIPS). These take the form of catalogs of stellar photometry (PHOTCAT) and linear polarimetry (POLCAT) in the near-infrared H-band (1.6 um) for four-hundred 10x10 arcmin fields of view that sample across the full Galactic longitude (L = 18 to 56 deg) and latitude ranges (B = -1 to +1 deg) of GPIPS. Several regions are represented as overlapping fields and have been mosaicked into preliminary Image Tiles (with polarization overlays). Some 60,000 stars as faint as H=12th exhibit significant polarizations and upper limits in these fields. Stars as faint as H=16-17th appear in the photometric catalog. This initial data release is via the GPIPS website (http://gpips0.bu.edu/) and will be linked to the VAO and Vizier.

GPIPS is being conducted on the 1.83m Perkins telescope outside Flagstaff, Arizona using the Mimir instrument configured as a near-infrared imaging polarimeter. A total of 3,237 10x10 arcmin fields will span 76 sq. deg of the inner, first quadrant Galactic plane. Data collection is more than 70% complete and should finish in 2013. The GPIPS data products (POLCAT, PHOTCAT, Image Tile Catalog) are being released on a rolling basis and as quickly as the data can be processed and calibrated. The second data release is expected for the fall and should contain nearly 1,000 fields.
Supported by NSF grants AST 06-07500 and 09-07790.

321.02

Galactic Plane Infrared Polarization Survey (GPIPS) - Example Science Applications

Michael D. Pavel¹, D. P. Clemens¹, A. F. Pinnick¹, J. M. Moreau¹, R. Marchwinski¹, M. Bartlett¹, B. Taylor^1
1Boston University.

4:40 PM - 4:50 PM

St. George CD

With the initial public release of GPIPS data for 400 fields, a wide range of new scientific studies is made possible. This talk will highlight some examples, so as to motivate broad use of this rich data set. Combining the GPIPS/PHOTCAT data products with 2MASS and UKIDSS will enable studies for NIR stellar variability and proper motion, as well as help resolve 2MASS source ambiguities and improve cluster photometry. The GPIPS/POLCAT polarization data catalogs enables mapping magnetic fields across a wide range of extinction, from Av = 1 to 20 mag or more, permitting tracing the field from the edges of molecular clouds to close to the most extincted cloud cores. In addition to assessing the roles played by the magnetic field in helping to order cool clouds and the star formation conditions within them through evaluating the mean field directions, POLCAT data may be analyzed with the Chandrasekhar-Fermi method to develop resolved magnetic field strength maps across fields. Also, comparisons of structure functions of cool cloud velocities and column densities may be compared to magnetic field structure functions to ascertain the relative importance of magnetohydrodynamic vs pure hydrodynamic turbulence. Finally, comparisons of the magnetic properties in the hot ISM, traced through Faraday rotation and synchrotron radiation, may be compared to the field properties in the cool ISM, atomic and molecular clouds, over the same lines of sight to gain an understanding of the coupling of the field across these vastly different ISM components.

Supported by NSF grants AST 06-07500 and AST 09-07790.

321.03

The Distance and Stability of the HI Filament that Comprises HVC A0

Gerrit L. Verschuur¹, D. L. Nidever^2
1University of Memphis, ²University of Virginia.

4:50 PM - 5:00 PM

St. George CD

The neutral hydrogen structure of high-velocity “cloud” A0 has been mapped using the Green Bank Telescope of the NRAO. The HI gas is in the form of a narrow, twisted filament with a typical line width of order 23 km/s within which regions of enhanced emission with line widths of order 4 to 6 km/s and as high as 15 km/s are located. Gaussian decomposition of the profiles is used to reveal the filament most clearly. If it is in equilibrium with surrounding galactic halo pressure its distance must be about 5,400 pc. However, the observed HI line widths are not a measure of the kinetic temperature of the gas. Instead their magnitude appears to be consistent with the presence of Alfvén waves for a magnetic field of order 2.8 µG. The existence of the bright, narrow line width features is more problematic. Geometry alone may account for their brightness and line widths. On the other hand, if the small-scale structures have angular scales of order 1.’5, lost inside the resolution of our data, these features, too, could be in equilibrium with halo pressure. In either case, the bright features exist relatively independent of the filament structure itself. This work suggests that the distance to HI filaments can be determined provided reliable estimates of surrounding gas pressure are available and if we are reasonably certain that a segment of filament is being viewed side-on.

321.04

The GALFA-HI Survey: Toward the Second Data Release

Kevin A. Douglas¹, J. E. G. Peek², J. Grcevich², D. Saul², M. Lee³, N. Pingel³, E. J. Korpela⁴, S. Stanimirovic³, M. E. Putman², S. J. Gibson⁵, C. E. Heiles^4
1NAIC, ²Columbia University, ³University of Wisconsin-Madison, ⁴University of California, Berkeley, ⁵Western Kentucky University.

5:00 PM - 5:10 PM

St. George CD

The GALFA-HI Survey uses 21-cm spectral line data recorded with the Arecibo L-band Feed Array (ALFA), in an effort to map the neutral hydrogen content of the Galaxy and its nearby environment. The first full public release of data (Peek et al. 2011, ApJS in press) covers approximately 7500 square degrees, from observations spanning the epoch of May 2005 to February 2009. The second data release will include data from GALFA-HI observations to the end of 2010. We will describe the attributes of the survey, and most importantly, how to gain access to the data.

321.05

Molecule Formation in the Heeschan-Riegel-Crutcher Cloud

D. Anish Roshi¹, N. G. Kantharia^2
1National Radio Astronomy Observatory, ²National Center for Radio Astrophysics, TIFR,, India.

5:10 PM - 5:20 PM

St. George CD

We report, for the first time, that the low frequency carbon recombination lines (CRRLs) from the innermost ∼ 10° of the Galaxy arise in the Heeschan-Riegel-Crutcher (HRC) cloud. The HRC cloud is amongst the most well known of HI self-absorbing (HISA) regions located at a distance of about 125 pc in the Galactic centre direction. We demonstrate that the physical properties of the HISA can be constrained by combining multi-frequency CRRL and HI observations.The derived physical properties of the HISA cloud are used to determine the cooling and heating rates. The dominant cooling process is emission of the CII 158 µm line whereas dominant heating process in the cloud interior is photoelectric emission. Constraints on the FUV flux (G0 ∼ 4 to 7) falling on the HRC cloud are obtained by assuming thermal balance between the dominant heating and cooling processes. The H$_2$ formation rate per unit volume in the cloud interior is ∼ 10$^{-10}$ -- 10$^{-12}$ s$^{-1}$ cm$^{-3}$, which far exceeds the H$_2$ dissociation rate per unit volume. We conclude that the self-absorbing cold HI gas in the HRC cloud may be in the process of converting to the molecular form. The cold HI gas observed as HISA features are ubiquitous in the inner Galaxy and form an important part of the ISM. Our analysis shows that combining CRRL and HI data can give valuable insight into the nature of these cold gas. We also present results from new low-frequency (< 800 MHz) CRRL observations toward HRC cloud using the Green Bank Telescope.

321.06

A Spitzer Survey of an Isolated Globule: DC314.8-5.1

Sachindev S. Shenoy¹, D. C. B. Whittet², Y. J. Pendleton³, C. Boersma¹, L. J. Allamandola⁴, D. Horne², P. A. Mayeur^2
1ORAU - NASA ARC, ²Rensselaer Polytechnic Institute, ³NASA Lunar Science Institute, ⁴NASA ARC.

5:20 PM - 5:30 PM

St. George CD

DC314.8-5.1 is an isolated globule in the constellation of Circinus in the southern hemisphere. A 10.53 V-magnitude B9 star is illuminating a reflection nebula in the eastern part of this cloud. We surveyed this cloud using data from Spitzer IRS, IRAC and MIPS instruments. The main goals of our survey are to use mid-IR photometry along with 2MASS data to determine if this globule is a site of active star formation and to use IR spectroscopy to detect PAHs and investigate the energetics in the cloud.

Here we describe preliminary results from the investigation of PAH emissions in DC314.8-5.1. Inspection of the IRAC 8 micron image shows widespread structured PAH emission towards this cloud. We have high resolution IRS spectra of HD130079 and low resolution IRS maps of the reflection nebula. In the spectral data we detect all the major PAH emissions in the 5~20 micron region. We find that the emission in the 12~14 micron region is quenched compared to the 11.3 micron feature suggesting most of the PAHs have solo hydrogen bonds. Spatial variation of PAH emissions seems to be identical as we move from the illuminating source, HD130079, towards the interior of the cloud except in the south-southwest region, where we see a slight enhancement. This enhancement is probably due to the skin effect (i.e., an excess due to viewing angle). We will analyze the ratios of various PAH features to i) put this globule in a global context with respect to the energetics of the region, and ii) determine the ionization state of the carrier molecules to investigate the interaction of PAHs with soft UV radiation. Combining results from the spectroscopic program with the stellar census data will provide new insight into the physical and evolutionary state of this isolated globule.

321.07

Measuring Dust with Pan-STARRs

Douglas P. Finkbeiner¹, E. F. Schlafly^1
1Harvard University.

5:30 PM - 5:40 PM

St. George CD

The colors of main sequence turnoff stars may be used to measure the reddening of the stars by foreground dust. Using Pan-STARRs 3 pi data, we have derived reddenings over a large part of the sky. I will show how these reddening measurements can be used as a calibration check of the PS1 data, and a test of the SFD (1998) dust map.

321.08

Turbulent Molecular Gas and Star Formation in the Shocked Intergalactic Medium of Stephan's Quintet

Pierre Guillard¹, F. Boulanger², A. Gusdorf³, M. Cluver¹, P. N. Appleton¹, G. Pineau des Forets², P. Ogle¹, U. Lisenfeld⁴, P. Duc⁵, E. Falgarone⁶, C. K. Xu^1
1Caltech, ²Institut d'Astrophysique Spatiale, France, ³Max Planck Institut für Radioastronomie, Germany, ⁴Departamento de Física Teórica y del Cosmos, Spain, ⁵AIM, Unité Mixte de Recherche CEA-CNRS, Université Paris VII, UMR 7158, France, ⁶ENS, LERMA, UMR 8112, CNRS, Observatoire de Paris, France.

5:40 PM - 5:50 PM

St. George CD

Spitzer spectroscopy has revealed a significant and diverse population of extragalactic sources where the mid-infrared rotational line emission of warm (> 150 K) molecular hydrogen (H2) is strongly enhanced, while star formation is suppressed. The multi-galaxy collision in Stephan's Quintet (SQ) is one example of these powerful H2 emitters. New CO line observations of the kpc-scale X-ray emitting shock associated with the collision will be presented. The CO gas is extremely turbulent, with FWHM up to 1000km/s, and the warm-to-cold H2 mass ratio is more than one order of magnitude higher than in star-forming galaxies. These observations provide insights into our understanding of how the mechanical energy of the galaxy collision is dissipated, and how this dissipation affects the passage from molecular gas to stars. This astrophysical process is relevant to many other active phases of galaxy evolution (AGN feedback, cooling flows, gas accretion, etc.) where a huge amount of mechanical energy is released in the ISM.

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