# Posts Tagged nucleus

## Recent Postings from nucleus

### Rummaging inside the Eskimo's parka: Variable asymmetric PN fast wind and a binary nucleus?

We report on high-resolution optical time-series spectroscopy of the central star of the `Eskimo’ planetary nebula NGC~2392. Datasets were secured with the ESO 2.3m in 2006 March and CFHT 3.6m in 2010 March to diagnose the fast wind and photospheric properties of the central star. The HeI and HeII recombination lines reveal evidence for clumping and temporal structures in the fast wind that are erratically variable on timescales down to ~ 30 min. (i.e. comparable to the characteristic wind flow time). We highlight changes in the overall morphology of the wind lines that cannot plausibly be explained by line-synthesis model predictions with a spherically homogeneous wind. Additionally we present evidence that the UV line profile morphologies support the notion of a high-speed, high-ionization polar wind in NGC~2392. Analyses of deep-seated, near-photospheric absorption lines reveals evidence for low-amplitude radial velocity shifts. Fourier analysis points tentatively to a ~ 0.12-d modulation in the radial velocities, independently evident in the ESO and CFHT data. We conclude that the overall spectroscopic properties support the notion of a (high inclination) binary nucleus in NGC~2392 and an asymmetric fast wind.

### Multiwavelength study of Cygnus A IV. Proper motion and location of the nucleus

Context. Cygnus A, as the nearest powerful FR II radio galaxy, plays an important role in understanding jets and their impact on the surrounding intracluster medium. Aims. To explain why the nucleus is observed superposed onto the eastern lobe rather than in between the two lobes, and why the jet and counterjet are non-colinear. Methods. We made a comparative study of the radio images at different frequencies of Cygnus A, in combination with the published results on the radial velocities in the Cygnus A cluster. Results. From the morphology of the inner lobes we conclude that the lobes are not interacting with one another, but are well separated, even at low radio frequencies. We explain the location of the nucleus as the result of the proper motion of the galaxy through the cluster. The required proper motion is of the same order of magnitude as the radial velocity offset of Cygnus A with the sub-cluster it belongs to. The proper motion of the galaxy through the cluster likely also explains the non-co-linearity of the jet and counterjet.

### Hubble Space Telescope Investigation of Main-Belt Comet 133P/Elst-Pizarro

We report new observations of the prototype main-belt comet (active asteroid) 133P/Elst-Pizarro taken at high angular resolution using the Hubble Space Telescope. The object has three main components; a) a point-like nucleus, b) a long, narrow antisolar dust tail and c) a short, sunward anti-tail. There is no resolved coma. The nucleus has a mean absolute magnitude H_V = 15.70+/-0.10 and a lightcurve range 0.42 mag., the latter corresponding to projected dimensions 3.6 x 5.4 km (axis ratio 1.5:1), at the previously measured geometric albedo of 0.05+/-0.02. We explored a range of continuous and impulsive emission models to simultaneously fit the measured surface brightness profile, width and position angle of the antisolar tail. Preferred fits invoke protracted emission, over a period of 150 days or less, of dust grains following a differential power-law size distribution with index 3.25 < q < 3.5 and having a wide range of sizes. Ultra-low surface brightness dust projected in the sunward direction is a remnant from emission activity occurring in previous orbits, and consists of the largest (>cm-sized) particles. Ejection velocities of one micron-sized particles are comparable to the ~1.8 m/s gravitational escape speed of the nucleus, while larger particles are released at speeds less than the gravitational escape velocity. The observations are consistent with, but do not prove, a hybrid hypothesis in which mass loss is driven by gas drag from the sublimation of near-surface water ice, but escape is aided by centripetal acceleration from the rotation of the elongated nucleus. No plausible alternative hypothesis has been identified.

### Near-Infrared long-slit spectra of Seyfert Galaxies: gas excitation across the central kiloparsec

The excitation of the gas phase of the interstellar medium can be driven by various mechanisms. In galaxies with an active nucleus, such as Seyfert galaxies, both radiative and mechanical energy from the central black hole, or the stars in the disk surrounding it may play a role. We investigate the relative importance and range of influence of the active galactic nucleus for the excitation of ionized and molecular gas in the central kiloparsec of its host galaxy. We present H- and K-band long-slit spectra for a sample of 21 nearby (D <70 Mpc) Seyfert galaxies obtained with the NIRSPEC instrument on the Keck telescope. For each galaxy, we fit the nebular line emission, stellar continua, and warm molecular gas as a function of distance from the nucleus. Our analysis does not reveal a clear difference between the nucleus proper and off-nuclear environment in terms of excitation mechanisms, suggesting that the influence of an AGN reaches far into the disk of the host galaxy. The radial variations in emission line ratios indicate that, while local mechanisms do affect the gas excitation, they are often averaged out when measuring over extended regions. The fully calibrated long-slit spectra, as well as our fitting results, are made available on-line.

### Gas inflows towards the nucleus of the active galaxy NGC7213

We present two-dimensional stellar and gaseous kinematics of the inner 0.8×1.1kpc^2 of the LINER/Seyfert 1 galaxy NGC7213, from optical spectra obtained with the GMOS integral field spectrograph on the Gemini South telescope at a spatial resolution of 60pc. The stellar kinematics shows an average velocity dispersion of 177km/s, circular rotation with a projected velocity amplitude of 50km/s and a kinematic major axis at a position angle of -4degrees (west of north). From the average velocity dispersion we estimate a black hole mass of M_BH=8_{-6}^{+16}x10^7 M_sun. The gas kinematics is dominated by non-circular motions, mainly along two spiral arms extending from the nucleus out to 4arcsec (280pc) to the NW and SE, that are cospatial with a nuclear dusty spiral seen in a structure map of the nuclear region of the galaxy. The projected gas velocities along the spiral arms show blueshifts in the far side and redshifts in the near side, with values of up to 200km/s. This kinematics can be interpreted as gas inflows towards the nucleus along the spiral arms if the gas is in the plane of the galaxy. We estimate the mass inflow rate using two different methods. The first is based of the observed velocities and geometry of the flow, and gives a mass inflow rate in the ionised gas of 7×10^-2 M_sun/yr. In the second method, we calculate the net ionised gas mass flow rate through concentric circles of decreasing radii around the nucleus resulting in mass inflow rates ranging from 0.4 M_sun/yr at 300pc down to 0.2 M_sun/yr at 100pc from the nucleus. These rates are larger than necessary to power the active nucleus.

### Analysis of nuclear activity of ten polar ring galaxies

The accumulation of mass from the interaction process that forms the polar ring galaxies is a factor that favors the conditions necessary to trigger nonthermal nuclear activities.. This fact encouraged the chemical analysis of ten polar ring galaxies. In order to verify the presence of an active nucleus in these galaxias, we built diagnostic diagrams using lines H{\beta}, [OIII], [HI], H{\alpha}, [NII], and [SII] and classified the type of nuclear activity. For galaxies that do not show shock, the parameters N2 and O3N2 were also determined. From this sample, we identified seven galaxies with an active nucleus and three that behave as HII regions. One galaxy with an active nucleus was classified as Seyfert. Although our data do not provide a statistically significant sample, we can speculate that polar ring galaxies are a setting conducive to trigger non-thermal nuclear activities.

### Exploring the origin, the nature and the dynamical behaviour of distant stars in galaxy models

We explore the regular or chaotic nature of orbits moving in the meridional plane of an axially symmetric galactic gravitational model with a disk, a dense spherical nucleus and some additional perturbing terms corresponding to influence from nearby galaxies. In order to obtain this we use the Smaller ALingment Index (SALI) technique integrating extensive samples of orbits. Of particular interest is the study of distant, remote stars moving in large galactocentric orbits. Our extensive numerical experiments indicate that the majority of the distant stars perform chaotic orbits. However, there are also distant stars displaying regular motion as well. Most distant stars are ejected into the galactic halo on approaching the dense and massive nucleus. We study the influence of some important parameters of the dynamical system, such as the mass of the nucleus and the angular momentum, by computing in each case the percentage of regular and chaotic orbits. A second order polynomial relationship connects the mass of the nucleus and the critical angular momentum of the distant star. Some heuristic semi-theoretical arguments to explain and justify the numerically derived outcomes are also given. Our numerical calculations suggest that the majority of distant stars spend their orbital time in the halo where it is easy to be observed. We present evidence that the main cause for driving stars to distant orbits is the presence of the dense nucleus combined with the perturbation caused by nearby galaxies. The origin of young O and B stars observed in the halo is also discussed.

### Exploring the origin, the nature and the dynamical behaviour of distant stars in galaxy models [Replacement]

We explore the regular or chaotic nature of orbits moving in the meridional plane of an axially symmetric galactic gravitational model with a disk, a dense spherical nucleus and some additional perturbing terms corresponding to influence from nearby galaxies. In order to obtain this we use the Smaller ALingment Index (SALI) technique integrating extensive samples of orbits. Of particular interest is the study of distant, remote stars moving in large galactocentric orbits. Our extensive numerical experiments indicate that the majority of the distant stars perform chaotic orbits. However, there are also distant stars displaying regular motion as well. Most distant stars are ejected into the galactic halo on approaching the dense and massive nucleus. We study the influence of some important parameters of the dynamical system, such as the mass of the nucleus and the angular momentum, by computing in each case the percentage of regular and chaotic orbits. A second order polynomial relationship connects the mass of the nucleus and the critical angular momentum of the distant star. Some heuristic semi-theoretical arguments to explain and justify the numerically derived outcomes are also given. Our numerical calculations suggest that the majority of distant stars spend their orbital time in the halo where it is easy to be observed. We present evidence that the main cause for driving stars to distant orbits is the presence of the dense nucleus combined with the perturbation caused by nearby galaxies. The origin of young O and B stars observed in the halo is also discussed.

### Evidence for nuclear radio jet and its structure down to <100 Schwarzschild radii in the center of the Sombrero galaxy (M 104, NGC 4594)

Abridged: We investigated the detailed radio structure of the nucleus of the Sombrero galaxy using high-resolution, quasi-simultaneous, multi-frequency, phase-referencing VLBA observations. We obtained the VLBI images toward this nucleus, with unprecedented sensitivities and resolutions, at the seven frequencies between 1.4 and 43 GHz, where those at 15, 24 and 43 GHz are the first clear VLBI detections. At 43 GHz, the nuclear structure was imaged on a linear scale under 100 Schwarzschild radii. For the first time, we have discovered the presence of the extended structure in this nucleus, which is directing from the radio core in two sides toward northwest/southeast directions. The nuclear structure shows a clear spatial gradient on the radio spectra, which is similar to that commonly seen in more luminous AGN with powerful relativistic jets. Moreover, the radio core shows a frequency-dependent size with an elongated shape, and the position of the core also tends to be frequency dependent. A set of these new findings provide evidence that the central engine of the Sombrero is powering radio jets. Based on the observed brightness ratio of jet-to-counter jet, core position shift and its comparison with a theoretical model, we constrained the following fundamental physical parameters for the M 104 jets: (1) the northern side is the approaching jet, whereas the southern side is receding: (2) the inclination angle of the jet is relatively close to our line-of-sight, probably less than ~25degrees: (3) the jet intrinsic velocity is highly sub-relativistic at a speed less than ~0.2c. The derived pole-on nature of the M 104 jet is in accordance with the previous argument that M 104 contains a true type II AGN, i.e., the broad line region of this nucleus is actually absent or intrinsically weak, if the plane of the presumed circumnuclear torus is perpendicular to the axis of the radio jets.

### The narrow X-ray tail and double H-alpha tails of ESO 137-002 in Abell 3627

We present the analysis of a deep Chandra observation of a ~2L_* late-type galaxy, ESO 137-002, in the closest rich cluster A3627. The Chandra data reveal a long (>40 kpc) and narrow tail with a nearly constant width (~3 kpc) to the southeast of the galaxy, and a leading edge ~1.5 kpc from the galaxy center on the upstream side of the tail. The tail is most likely caused by the nearly edge-on stripping of ESO 137-002′s ISM by ram pressure, compared to the nearly face-on stripping of ESO 137-001 discussed in our previous work. Spectral analysis of individual regions along the tail shows that the gas throughout it has a rather constant temperature, ~1 keV, very close to the temperature of the tails of ESO 137-001, if the same atomic database is used. The derived gas abundance is low (~0.2 solar with the single-kT model), an indication of the multiphase nature of the gas in the tail. The mass of the X-ray tail is only a small fraction (<5%) of the initial ISM mass of the galaxy, suggesting that the stripping is most likely at an early stage. However, with any of the single-kT, double-kT and multi-kT models we tried, the tail is always "over-pressured" relative to the surrounding ICM, which could be due to the uncertainties in the abundance, thermal vs. non-thermal X-ray emission, or magnetic support in the ICM. The H-alpha data from SOAR show a ~21 kpc tail spatially coincident with the X-ray tail, as well as a secondary tail (~12 kpc long) to the east of the main tail diverging at an angle of ~23 degrees and starting at a distance of ~7.5 kpc from the nucleus. At the position of the secondary H-alpha tail, the X-ray emission is also enhanced at the ~2 sigma level. We compare the tails of ESO 137-001 and ESO 137-002, and also compare the tails to simulations. Both the similarities and differences of the tails pose challenges to the simulations. Several implications are briefly discussed.

### Unveiling the Influence of Dark Matter in Axially Symmetric Galaxies

We investigate the regular or chaotic nature of orbits of stars moving in the meridional plane (R,z) of an axially symmetric galactic model with a dense, massive spherical nucleus and a dark matter halo component. In particular, we study the influence of the fractional portion of the dark matter, by computing in each case the percentage of chaotic orbits, as well as the percentages of orbits of the main regular resonant families. In an attempt to distinguish between regular and chaotic motion, we use the Fast Lyapunov Indicator (FLI) method to extensive samples of orbits obtained by integrating numerically the equations of motion as well as the variational equations. Furthermore, a technique which is based mainly on the field of spectral dynamics that utilizes the Fourier transform of the time series of each coordinate is used for identifying the various families of regular orbits and also to recognize the secondary resonances that bifurcate from them. Two cases are studied in our work: (i) the case where we have a disk galaxy model (ii) the case where our model represents an elliptical galaxy. Comparison with early related work is also made.

### Refining the M_BH-V_c scaling relation with HI rotation curves of water megamaser galaxies

Black hole – galaxy scaling relations provide information about the coevolution of supermassive black holes and their host galaxies. We compare the black hole mass – circular velocity (MBH – Vc) relation with the black hole mass – bulge stellar velocity dispersion (MBH – sigma) relation, to see whether the scaling relations can passively emerge from a large number of mergers, or require a physical mechanism, such as feedback from an active nucleus. We present VLA H I observations of five galaxies, including three water megamaser galaxies, to measure the circular velocity. Using twenty-two galaxies with dynamical MBH measurements and Vc measurements extending to large radius, our best-fit MBH – Vc relation, log MBH = alpha + beta log(Vc /200 km s^-1), yields alpha = 7.43+/-0.13, beta = 3.68+1.23/-1.20, and intrinsic scatter epsilon_int = 0.51+0.11/-0.09. The intrinsic scatter may well be higher than 0.51, as we take great care to ascribe conservatively large observational errors. We find comparable scatter in the MBH – sigma relations, epsilon_int = 0.48+0.10/-0.08, while pure merging scenarios would likely result in a tighter scaling with the dark halo (as traced by Vc) than baryonic (sigma) properties. Instead, feedback from the active nucleus may act on bulge scales to tighten the MBH – sigma relation with respect to the MBH – Vc relation, as observed.

### On the nature of the brightest globular cluster in M81

We analyse the photometric, chemical, star formation history and structural properties of the brightest globular cluster (GC) in M81, referred as GC1 in this work, with the intention of establishing its nature and origin. We find that it is a metal-rich ([Fe/H]=-0.60+/-0.10), alpha-enhanced ([Alpha/Fe]=0.20+/0.05), core-collapsed (core radius r_c=1.2 pc, tidal radius r_t = 76r_c), old (>13 Gyr) cluster. It has an ultraviolet excess equivalent of ~2500 blue horizontal branch stars. It is detected in X-rays indicative of the presence of low-mass binaries. With a mass of 10 million solar masses, the cluster is comparable in mass to M31-G1 and is four times more massive than Omega Cen. The values of r_c, absolute magnitude and mean surface brightness of GC1 suggest that it could be, like massive GCs in other giant galaxies, the left-over nucleus of a dissolved dwarf galaxy.

### 17P/Holmes: Contrast in activity between before and after the 2007 outburst

A Jupiter-family comet, 17P/Holmes, underwent outbursts in 1892 and 2007. In particular, the 2007 outburst is known as the greatest outburst over the past century. However, little is known about the activity before the outburst because it was unpredicted. In addition, the time evolution of the nuclear physical status has not been systematically studied. Here we study the activity of 17P/Holmes before and after the 2007 outburst through optical and mid-infrared observations. We found that the nucleus highly depleted its near-surface icy component before but became activated after the 2007 outburst. Assuming a conventional 1-um-sized grain model, we derived a surface fractional active area of 0.58% +- 0.14% before the outburst whereas it was enlarged by a factor of ~50 after the 2007 outburst. We also found that large (>=1 mm) particles could be dominant in the dust tail observed around aphelion. Based on the size of the particles, the dust production rate was >=170 kg/s at the heliocentric distance rh = 4.1 AU, suggesting that the nucleus still held active status around the aphelion passage. The nucleus color was similar to that of the dust particles and average for a Jupiter-family comet but different from most Kuiper Belt objects, implying that the color may be inherent to icy bodies in the solar system. On the basis of these results, we concluded that more than 76 m surface materials were blown off by the 2007 outburst.

### Observing supernova neutrino light curve in future dark matter detectors

The possibility of observing supernova (SN) neutrinos through the process of coherent elastic neutrino-nucleus scattering (CENNS) in future ton scale detectors designed primarily for direct detection of dark matter is investigated. In particular, we focus on the possibility of distinguishing the various phases of the SN neutrino emission. The neutrino emission rates from the recent long term Basel/Darmstadt simulations are used to calculate the expected event rates. The recent state-of-the-art SN simulations predict closer fluxes among different neutrino flavors and lower average energies compared to the earlier simulation models. We find that our estimated total event rates are typically a factor of two lower than those predicted using older simulation models. We further find that, with optimistic assumptions on the detector’s time resolution (~ 10 ms) and energy threshold (~ 0.1 keV), the neutrinos associated with the accretion phase of the SN can in principle be demarcated out with, for example, a 10-ton Xe detector, although distinguishing the neutrinos associated with the neutronization burst phase of the explosion would typically require several tens of ton detectors. We also comment on the possibility of studying the properties of non-electron flavor neutrinos from the CENNS of SN neutrinos.

### A Chandra view of the clumpy reflector at the heart of the Circinus galaxy

We present a spectral and imaging analysis of the X-ray reflecting structure at the heart of the Circinus galaxy, investigating the innermost regions surrounding the central black hole. By studying an archival 200 ks Chandra ACIS-S observation, we are able to image the extended clumpy structure responsible for both cold reflection of the primary radiation and neutral iron Ka line emission. We measure an excess of the equivalent width of the iron Ka line which follows an axisymmetric geometry around the nucleus on a hundred pc scale. Spectra extracted from different regions confirm a scenario in which the dominant mechanism is the reflection of the nuclear radiation from Compton-thick gas. Significant differences in the equivalent width of the iron Ka emission line (up to a factor of 2) are found. It is argued that these differences are due to different scattering angles with respect to the line of sight rather than to different iron abundances.

### Cross-Section Measurements of the 86Kr(g,n) Reaction to Probe the s-Process Branching at 85Kr

We have carried out photodisintegration cross-section measurements on 86Kr using monoenergetic photon beams ranging from the neutron separation energy, S_n = 9.86 MeV, to 13 MeV. We combine our experimental 86Kr(g,n)85Kr cross section with results from our recent 86Kr(g,g’) measurement below the neutron separation energy to obtain the complete nuclear dipole response of 86Kr. The new experimental information is used to predict the neutron capture cross section of 85Kr, an important branching point nucleus on the abundance flow path during s-process nucleosynthesis. Our new and more precise 85Kr(n,g)86Kr cross section allows to produce more precise predictions of the 86Kr abundance from s-process models. In particular, we find that the models of the s-process in asymptotic giant branch stars of mass < 1.5 Msun, where the 13C neutron source burns convectively rather than radiatively, represent a possible solution for the highest 86Kr/82Kr ratios observed in meteoritic stardust SiC grains.

### Episodic radio galaxies J0116$-$4722 and J1158+2621: can we constrain the quiescent phase of nuclear activity?

We present multifrequency radio observations of two well known episodic FR\,II radio galaxies (J0116$-$4722 and J1158+2621) and a detailed investigation of the life-cycle of episodic radio galaxies from their spectral and radiative properties. Combining our previous work with the present results, we either constrain or place very good limits on the active and quiescent phases of a small sample of episodic FR\,II radio galaxies. The duration of the quiescent phase can be as small as the hotspot fading time of the previous episode, and as high as a few tens of Myr; however, for none of the sources in our sample is it close to the duration of the active phase of the previous episode. We also find that for many episodic radio galaxies, the nucleus is variable at radio wavelengths. For our small sample of 7 episodic radio galaxies, we find 4 to have strongly variable cores, a much larger proportion than is generally found in samples of normal FR\,II radio galaxies. Studies with larger samples will be required to establish a statistical association between core variability and episodic radio activity.

### Luminous Infrared Galaxies With the Submillimeter Array. IV. 12CO J=6-5 Observations of VV 114

We present high-resolution (~2.5") observations of 12CO J=6-5 towards the luminous infrared galaxy VV 114 using the Submillimeter Array. We detect 12CO J=6-5 emission from the eastern nucleus of VV 114 but do not detect the western nucleus or the central region. We combine the new 12CO J=6-5 observations with previously published or archival low-J CO observations, that include 13CO J=1-0 Atacama Large Millimeter/submillimeter Array cycle 0 observations, to analyze the beam-averaged physical conditions of the molecular gas in the eastern nucleus. We use the radiative transfer code RADEX and a Bayesian likelihood code to constrain the temperature (T_kin), density (n(H2)) and column density (N(12CO)) of the molecular gas. We find that the most probable scenario for the eastern nucleus is a cold (T_kin = 38 K), moderately dense (n(H2) = 10^2.89 cm^-3) molecular gas component. We find the most probable 12CO to 13CO abundance ratio ([12CO]/[13CO]) is 229, roughly three times higher than the Milky Way value. This high abundance ratio may explain the observed high 12CO/ 13CO line ratio (> 25). The unusual 13CO J=2-1/J=1-0 line ratio of 0.6 is produced by a combination of moderate 13CO optical depths (tau = 0.4 – 1.1) and extremely subthermal excitation temperatures. We measure the CO-to-H2 conversion factor, alpha_co to be 0.5 M_sol (K km s^-1 pc^2)^-1, which agrees with the widely used factor for ultra luminous infrared galaxies of Downes & Solomon (1998; alpha_co =0.8 M_sol (K km s^-1 pc^2)^-1).

### Signatures of Dark Matter Scattering Inelastically Off Nuclei

Direct dark matter detection focuses on elastic scattering of dark matter particles off nuclei. In this study, we explore inelastic scattering where the nucleus is excited to a low-lying state of 10-100 keV, with subsequent prompt de-excitation. We calculate the inelastic structure factors for the odd-mass xenon isotopes based on state-of-the-art large-scale shell-model calculations with chiral effective field theory WIMP-nucleon currents. For these cases, we find that the inelastic channel is comparable to or can dominate the elastic channel for momentum transfers around 150 MeV. We calculate the inelastic recoil spectra in the standard halo model, compare these to the elastic case, and discuss the expected signatures in a xenon detector, along with implications for existing and future experiments. The combined information from elastic and inelastic scattering will allow to determine the dominant interaction channel within one experiment. In addition, the two channels probe different regions of the dark matter velocity distribution and can provide insight into the dark halo structure. The allowed recoil energy domain and the recoil energy at which the integrated inelastic rates start to dominate the elastic channel depend on the mass of the dark matter particle, thus providing a potential handle to constrain its mass.

### Relating Changes in Cometary Rotation to Activity: Current Status and Applications to Comet C/2012 S1 (ISON)

We introduce a parameter, X, to predict the changes in the rotational period of a comet in terms of the rotational period itself, the nuclear radius, and the orbital characteristics. We show that X should be a constant if the bulk densities and shapes of nuclei are nearly identical and the activity patterns are similar for all comets. For four nuclei for which rotational changes are well documented, despite the nearly factor 30 variation observed among the effective active fractions of these comets, X is constant to within a factor two. We present an analysis for the sungrazing comet C/2012 S1 (ISON) to explore what rotational changes it could undergo during the upcoming perihelion passage where its perihelion distance will be ~2.7 solar radii. When close to the sun, barring a catastrophic disruption of the nucleus, the activity of ISON will be sufficiently strong to put the nucleus into a non-principal-axis rotational state and observable changes to the rotational period should also occur. Additional causes for rotational state changes near perihelion for ISON are tidal torques caused by the sun and the significant mass loss due to a number of mechanisms resulting in alterations to the moments of inertia of the nucleus.

### Breaking the Obscuring Screen: A Resolved Molecular Outflow in a Buried QSO

We present Keck laser guide star adaptive optics observations of the nearby buried QSO F08572+3915:NW. We use near-infrared integral field data taken with OSIRIS to reveal a compact disk and molecular outflow using Pa-alpha and H_2 rotational-vibrational transitions at a spatial resolution of 100 pc. The outflow emerges perpendicular to the disk into a bicone of one-sided opening angle 100 degrees up to distances of 400 pc from the nucleus. The integrated outflow velocities, which reach at least -1300 km/s, correspond exactly to those observed in (unresolved) OH absorption, but are smaller (larger) than those observed on larger scales in the ionized (neutral atomic) outflow. These data represent a factor of >10 improvement in the spatial resolution of molecular outflows from mergers/QSOs, and plausibly represent the early stages of the excavation of the dust screen from a buried QSO.

### Regional variations in the dense gas heating and cooling in M51 from Herschel far-infrared spectroscopy

We present Herschel PACS and SPIRE spectroscopy of the most important far-infrared cooling lines in M51, [CII](158 \mu m), [NII](122 & 205 \mu m), [OI](63 and 145 \mu m) and [OIII](88 \mu m). We compare the observed flux of these lines with the predicted flux from a photon dominated region model to determine characteristics of the cold gas such as density, temperature and the far-ultraviolet radiation field, G_0, resolving details on physical scales of roughly 600 pc. We find an average [CII]/F_TIR of 4 x 10^{-3}, in agreement with previous studies of other galaxies. A pixel-by-pixel analysis of four distinct regions of M51 shows a radially decreasing trend in both the far-ultraviolet (FUV) radiation field, G_0 and the hydrogen density, n, peaking in the nucleus of the galaxy, then falling off out to the arm and interarm regions. We see for the first time that the FUV flux and gas density are similar in the differing environments of the arm and interarm regions, suggesting that the inherent physical properties of the molecular clouds in both regions are essentially the same.

### Fourth generation Majorana neutrino, dark matter and Higgs physics [Cross-Listing]

We consider extensions of the standard model with fourth generation fermions (SM4) in which extra symmetries are introduced such that the transitions between the fourth generation fermions and the ones in the first three generations are forbidden. In these models, the stringent lower bounds on the masses of fourth generation quarks from direct searches are relaxed, and the lightest fourth neutrino is allowed to be stable and light enough to trigger the Higgs boson invisible decay. In addition, the fourth Majorana neutrino can be a subdominant but highly detectable dark matter component. We perform a global analysis of the current LHC data on the Higgs production and decay in this type of SM4. The results show that the mass of the lightest fourth Majorana neutrino is confined in the range $\sim 41-59$ GeV. Within the allowed parameter space, the predicted effective cross-section for spin-independent DM-nucleus scattering is $\sim 3\times 10^{-48}-6\times 10^{-46} \text{cm}^{2}$, which is close to the current Xenon100 upper limit and is within the reach of the Xenon1T experiment in the near future. The predicted spin-dependent cross sections can also reach $\sim 8\times 10^{-40}\text{cm}^{2}$.

### Multi-pomeron repulsion and the Neutron-star mass [Cross-Listing]

A multi-pomeron exchange potential (MPP) is proposed as a model for the three-body repulsion indicated in neutron-star matter, which works universally among three- and four-baryons. Its strength is determined by analyzing the nucleus-nucleus scattering with the G-matrix folding model. The EoS in neutron matter is obtained including the MPP contribution. The neutron-star mass is calculated by solving the TOV equation. The maximum mass is obtained to be larger than the observed one $1.97 M_{solar}$ on the basis of the experimental data.

### Millimetre continuum observations of comet C/2009 P1 (Garradd)

Little is known about the physical properties of the nuclei of Oort cloud comets. Measuring the thermal emission of a nucleus is one of the few means for deriving its size and constraining some of its thermal properties. We attempted to measure the nucleus size of the Oort cloud comet C/2009 P1 (Garradd). We used the Plateau de Bure Interferometer to measure the millimetric thermal emission of this comet at 157 GHz (1.9 mm) and 266 GHz (1.1 mm). Whereas the observations at 266 GHz were not usable due to bad atmospheric conditions, we derived a 3-sigma upper limit on the comet continuum emission of 0.41 mJy at 157 GHz. Using a thermal model for a spherical nucleus with standard thermal parameters, we found an upper limit of 5.6 km for the radius. The dust contribution to our signal is estimated to be negligible. Given the water production rates measured for this comet and our upper limit, we estimated that Garradd was very active, with an active fraction of its nucleus larger than 50%.

### Beginning of activity in 67P/Churyumov-Gerasimenko and predictions for 2014/5

Comet 67P/Churyumov-Gerasimenko was selected in 2003 as the new target of the Rosetta mission. It has since been the subject of a detailed campaign of observations to characterise its nucleus and activity. Here we present previously unpublished data taken around the start of activity of the comet in 2007/8, before its last perihelion passage. We constrain the time of the start of activity, and combine this with other data taken throughout the comet’s orbit to make predictions for its likely behaviour during 2014/5 while Rosetta is operating. A considerable difficulty in observing 67P during the past years has been its position against crowded fields towards the Galactic centre for much of the time. The 2007/8 data presented here were particularly difficult, and the comet will once again be badly placed for Earth-based observations in 2014/5. We make use of the difference image analysis (DIA) technique, which is commonly used in variable star and exoplanet research, to remove background sources and extract images of the comet. In addition, we reprocess a large quantity of archival images of 67P covering its full orbit, to produce a heliocentric lightcurve. By using consistent reduction, measurement and calibration techniques we generate a remarkably clean lightcurve, which can be used to measure a brightness-distance relationship and to predict the future brightness of the comet. We determine that the comet was active around November 2007, at a pre-perihelion distance from the Sun of 4.3 AU. The comet will reach this distance, and probably become active again, in March 2014. We find that the dust brightness can be well described by Af\rho \propto r^-3.2 pre-perihelion and r^-3.4 post-perihelion, and that the comet has a higher dust-to-gas ratio than average. A model fit to the photometric data suggests that only a small fraction (1.4%) of the surface is active.

### Solution of the alpha-potential mystery in the gamma-process and its impact on the Nd/Sm ratio in meteorites

The 146Sm/144Sm ratio in the early solar system has been constrained by Nd/Sm isotope ratios in meteoritic material. Predictions of 146Sm and 144Sm production in the gamma-process in massive stars are at odds with these constraints and this is partly due to deficiences in the prediction of the reaction rates involved. The production ratio depends almost exclusively on the (gamma,n)/(gamma,alpha) branching at 148Gd. A measurement of 144Sm(alpha,gamma)148Gd at low energy had discovered considerable discrepancies between cross section predictions and the data. Although this reaction cross section mainly depends on the optical alpha+nucleus potential, no global optical potential has yet been found which can consistently describe the results of this and similar alpha-induced reactions at the low energies encountered in astrophysical environments. The untypically large deviation in 144Sm(alpha,gamma) and the unusual energy dependence can be explained, however, by low-energy Coulomb excitation which is competing with compound nucleus formation at very low energies. Considering this additional reaction channel, the cross sections can be described with the usual optical potential variations, compatible with findings for (n,alpha) reactions in this mass range. Low-energy (alpha,gamma) and (alpha,n) data on other nuclei can also be consistently explained in this way. Since Coulomb excitation does not affect alpha-emission, the 148Gd(gamma,alpha) rate is much higher than previously assumed. This leads to small 146Sm/144Sm stellar production ratios, in even more pronounced conflict with the meteorite data.

### The location and impact of jet-driven outflows of cold gas: the case of 3C293

The nearby radio galaxy 3C293 is one of a small group of objects where extreme outflows of neutral hydrogen have been detected. However, due to the limited spatial resolution of previous observations, the exact location of the outflow was not able to be determined. In this letter, we present new higher resolution VLA observations of the central regions of this radio source and detect a fast outflow of HI with a FWZI velocity of \Delta v~1200 km/s associated with the inner radio jet, approximately 0.5 kpc west of the central core. We investigate possible mechanisms which could produce the observed HI outflow and conclude that it is driven by the radio-jet. However, this outflow of neutral hydrogen is located on the opposite side of the nucleus to the outflow of ionised gas previously detected in this object. We calculate a mass outflow rate in the range of 8-50 solar masses/yr corresponding to a kinetic energy power injected back into the ISM of 1.38×10^{42} – 1.00×10^{43} erg/s or 0.01 – 0.08 percent of the Eddington luminosity. This places it just outside the range required by some galaxy evolution simulations for negative feedback from the AGN to be effective in halting star-formation within the galaxy.

### Orbit classification in the meridional plane of a disk galaxy model with a spherical nucleus

We investigate the regular or chaotic nature of star orbits moving in the meridional plane of an axially symmetric galactic model with a disk and a spherical nucleus. We study the influence of some important parameters of the dynamical system, such as the mass and the scale length of the nucleus, the angular momentum or the energy, by computing in each case the percentage of chaotic orbits, as well as the percentages of orbits of the main regular resonant families. Some heuristic arguments to explain and justify the numerically derived outcomes are also given. Furthermore, we present a new method to find the threshold between chaos and regularity for both Lyapunov Characteristic Numbers and SALI, by using them simultaneously.

### Incidence of Strong MgII Absorbers Towards Different Types of Quasars

We report the first comparative study of strong MgII absorbers seen towards radio-loud quasars of core-dominated (CDQs) and lobe-dominated (LDQs) types and normal QSOs. The MgII associated absorption systems having a velocity offset v < 5000km/s from the systemic velocity of the background quasar were also excluded. Existing spectroscopic data for redshift-matched sightlines of 3975 CDQs and 1583 LDQs, covering a emission redshift range 0.39-4.87, were analysed and 864 strong MgII absorbers were found, covering the redshift range 0.45-2.17. The conclusions reached using this well-defined large dataset of strong MgII absorbers are: (i) The number density, dN/dz, towards CDQs shows a small, marginally significant excess over the estimate available for QSOs; (ii) In the redshift space, this difference is reflected in terms of a 1.6sigma excess of dN/dz over the QSOs, within the narrow redshift interval 1.2-1.8; (iii) The dN/dbeta distribution (with beta=v/c) for CDQs shows a significant excess over the distribution found for a redshift and luminosity matched sample of QSOs, at beta in the range 0.05-0.1. This leads us to infer that a significant fraction of strong MgII absorption systems seen in this offset velocity range are probably associated with the CDQs and might be accelerated into the line of sight by their powerful jets and/or due to the accretion-disk outflows close to our direction. Support to this scenario comes from a consistency check in which we only consider the spectral range corresponding to beta > 0.2. The computed redshift distribution for strong MgII absorbers towards CDQs now shows excellent agreement with that known for QSOs, as indeed is expected for purely intervening absorption systems. Thus, it appears that for CDQs the associated strong MgII absorbers can be seen at much larger velocities relative to the nucleus than the commonly adopted upper limit of 5000km/s.

### High-density Molecular Gas Properties of the Starburst Galaxy NGC 1614 Revealed with ALMA

We present the results of HCN/HCO+/HNC J=4-3 transition line observations of the nearby starburst galaxy NGC 1614, obtained with ALMA Cycle 0. We find that high density molecular gas, traced with these lines, shows a velocity structure such that the northern (southern) side of the nucleus is redshifted (blueshifted) with respect to the nuclear velocity of this galaxy. The redshifted and blueshifted emission peaks are offset by ~0.6" at the northern and southern sides of the nucleus, respectively. At these offset positions, observations at infrared >3 micron indicate the presence of active dusty starbursts, supporting the picture that high-density molecular gas is the site of active starbursts. The enclosed dynamical mass within the central ~2" in radius, derived from the dynamics of the high-density molecular gas, is ~10^9 Msun, which is similar to previous estimates. Finally, the HCN emission is weaker than HCO+ but stronger than HNC for J=4-3 for all starburst regions of NGC 1614, as seen for J=1-0 transition lines in starburst-dominated galaxies.

### Three-body calculations of triple-alpha reaction [Cross-Listing]

Recently, the triple-\alpha (3\alpha) process, by which three 4He nuclei are fused into a 12C nucleus in stars, was studied by different methods in solving the quantum mechanical three-body problem. Their results of the thermonuclear reaction rate for the process differ by several orders at low stellar temperatures of 10^7 – 10^8 K. In this paper, we will present calculations of the 3\alpha process by a modified Faddeev three-body formalism in which the long-range effects of Coulomb interactions are accommodated. The reaction rate of the process is calculated via an inverse process, three-alpha (3-\alpha) photodisintegration of a 12C nucleus. Calculated reaction rate is about 10 times larger than that of the Nuclear Astrophysics Compilation of Reaction Rates (NACRE) at 10^7 K, and is remarkably smaller than the results of the recent three-body calculations. We will discuss a possible reason of the difference.

### Large-scale nuclear structure calculations for spin-dependent WIMP scattering with chiral effective field theory currents [Cross-Listing]

We perform state-of-the-art large-scale shell-model calculations of the structure factors for elastic spin-dependent WIMP scattering off 129,131Xe, 127I, 73Ge, 19F, 23Na, 27Al, and 29Si. This comprehensive survey covers the non-zero-spin nuclei relevant to direct dark matter detection. We include a pedagogical presentation of the formalism necessary to describe elastic and inelastic WIMP-nucleus scattering. The valence spaces and nuclear interactions employed have been previously used in nuclear structure calculations for these mass regions and yield a good spectroscopic description of these isotopes. We use spin-dependent WIMP-nucleus currents based on chiral effective field theory (EFT) at the one-body level and including the leading long-range two-body currents due to pion exchange, which are predicted in chiral EFT. Results for all structure factors are provided with theoretical error bands due to the nuclear uncertainties of WIMP currents in nuclei.

### Large-scale nuclear structure calculations for spin-dependent WIMP scattering with chiral effective field theory currents [Replacement]

We perform state-of-the-art large-scale shell-model calculations of the structure factors for elastic spin-dependent WIMP scattering off 129,131Xe, 127I, 73Ge, 19F, 23Na, 27Al, and 29Si. This comprehensive survey covers the non-zero-spin nuclei relevant to direct dark matter detection. We include a pedagogical presentation of the formalism necessary to describe elastic and inelastic WIMP-nucleus scattering. The valence spaces and nuclear interactions employed have been previously used in nuclear structure calculations for these mass regions and yield a good spectroscopic description of these isotopes. We use spin-dependent WIMP-nucleus currents based on chiral effective field theory (EFT) at the one-body level and including the leading long-range two-body currents due to pion exchange, which are predicted in chiral EFT. Results for all structure factors are provided with theoretical error bands due to the nuclear uncertainties of WIMP currents in nuclei.

### Dynamics of Large Fragments in the Tail of Active Asteroid P/2010 A2

We examine the motions of large fragments at the head of the dust tail of active asteroid P/2010 A2. In previous work we showed that these fragments were ejected from the primary nucleus in early 2009, either following a hypervelocity impact or by rotationally induced break-up. Here, we follow their positions through a series of Hubble Space Telescope images taken during the first half of 2010. The orbital evolution of each fragment allows us to constrain its velocity relative to the main nucleus after leaving its sphere of gravitational influence. We find that the fragments constituting a prominent X-shaped tail feature were emitted in a direction opposite to the motion of the asteroid and towards the south of its orbital plane. Derived emission velocities of these primary fragments range between 0.02 and 0.3 m/s, comparable to the ~0.08 m/s gravitational escape speed from the nucleus. Their sizes are on the order of decimeters or larger. We obtain the best fits to our data with ejection velocity vectors lying in a plane that includes the nucleus. This may suggest that the cause of the disruption of P/2010 A2 is rotational break-up.

### Kinematics of the intermediate mass black hole candidate HLX-1

We studied the optical spectrum of HLX-1 during its latest outburst, using the FORS2 spectrograph on the Very Large Telescope. We detect an Halpha emission line centered at lambda = (6718.9 +/- 0.9) Ang and find that its projected radial velocity with respect to the nucleus of ESO243-49 is (424 +/- 27) km/s, while the maximum rotational velocity of the stars in that galaxy is ~209 km/s. This suggests that HLX-1 and its surrounding stars were not formed in situ, but came either from a disrupted dwarf galaxy or from a nuclear recoil. We also find that the Halpha emission line is resolved with full width at half maximum ~400 km/s, suggesting a nebular rather than disk origin for the emission. Its luminosity (L_{Halpha} ~ a few 10^{37} erg/s, equivalent width ~70 Ang) is also consistent with emission from a nebula photo-ionized by HLX-1.

### EUV and X-Ray Observations of Comet Lovejoy (C/2011 W3) in the Lower Corona

We present an analysis of EUV and soft X-ray emission detected toward Comet Lovejoy (C/2011 W3) during its post-perihelion traverse of the solar corona on December 16, 2011. Observations were recorded by the Atmospheric Imaging Assembly (AIA) aboard the Solar Dynamics Observatory and the X-Ray Telescope (XRT) aboard Hinode. A single set of contemporaneous images is explored in detail, along with prefatory consideration for time evolution using only the 171 A data. For each of the eight passbands, we characterize the emission and derive outgassing rates where applicable. As material sublimates from the nucleus and is immersed in coronal plasma, it rapidly ionizes through charge states seldom seen in this environment. The AIA data show four stages of oxygen ionization (O III – O VI) along with C IV, while XRT likely captured emission from O VII, a line typical of the corona. With a nucleus of at least several hundred meters upon approach to a perihelion that brought the comet to within 0.2 solar radii of the photosphere, Lovejoy was the most significant sungrazer in recent history. Correspondingly high outgassing rates on the order of 10^32.5 oxygen atoms per second are estimated. Assuming that the neutral oxygen comes from water, this translates to a mass-loss rate of about 9.5E9 g/s, and based only on the 171 A observations, we find a total mass loss of approximately 10^13 g over the AIA egress. Additional and supporting analyses include a differential emission measure to characterize the coronal environment, consideration for the opening angle, and a comparison of the emission’s leading edge with the expected position of the nucleus.

### Morphogenesis of defects and tactoids during isotropic-nematic phase transition in self-assembled lyotropic chromonic liquid crystals [Cross-Listing]

We explore the structure of nuclei and topological defects in the first-order phase transition between the nematic (N) and isotropic (I) phases in lyotropic chromonic liquid crystals (LCLCs). The LCLCs are formed by self-assembled molecular aggregates of various lengths and show a broad biphasic region. The defects emerge as a result of two mechanisms. 1) Surface anisotropy mechanism that endows each N nucleus (tactoid) with topological defects thanks to preferential (tangential) orientation of the director at the closed I-N interface, and 2) Kibble mechanism with defects forming when differently oriented N tactoids merge with each other. Different scenarios of phase transition involve positive (N-in-I) and negative (I-in-N) tactoids with non-trivial topology of the director field and also multiply connected tactoids-in-tactoids configurations. The closed I-N interface limiting a tactoid shows a certain number of cusps; the lips of the interface on the opposite sides of the cusp make an angle different from pi. The N side of each cusp contains a point defect-boojum. The number of cusps shows how many times the director becomes perpendicular to the I-N interface when one circumnavigates the closed boundary of the tactoid. We derive conservation laws that connect the number of cusps c to the topological strength m of defects in the N part of the simply-connected and multiply-connected tactoids. We demonstrate how the elastic anisotropy of the N phase results in non-circular shape of the disclination cores. A generalized Wulff construction is used to derive the shape of I and N tactoids as the function of I-N interfacial tension anisotropy in the frozen director field of various topological charges m. The complex shapes and structures of tactoids and topological defects demonstrate an important role of surface anisotropy in morphogenesis of phase transitions in liquid crystals.