Gravitational wave bursts produced by supermassive binary black hole mergers will leave a persistent imprint on the space-time metric. Such gravitational wave memory signals are detectable by pulsar timing arrays as a glitch event that would seem to occur simultaneously for all pulsars. In this paper, we describe an initial algorithm which can be used to search for gravitational wave memory signals. We apply this algorithm to the Parkes Pulsar Timing Array data set. No significant gravitational wave memory signal is founded in the data set.

Distance measurements of gamma-ray pulsars are challenging questions in present pulsar studies. The Large Area Telescope (LAT) aboard the Fermi gamma-ray observatory discovered more than 100 gamma-ray pulsars, including 34 new gamma-selected pulsars which nearly have no distance information. We study the relation between gamma-ray emission efficiency (η=Lγ/Ė) and pulsar parameters, for young radio-selected gamma-ray pulsars with known distance information. We have introduced three generation order parameters to describe gamma-ray emission properties of pulsars, and find a strong correlation between η and ζ3, the generation order parameter which reflects γ-ray photon generations in pair cascade processes induced by magnetic field absorption in pulsar magnetosphere. A good correlation between η and BLC, the magnetic field at the light cylinder radius, is also found. These correlations can serve as distance indicators in gamma-ray pulsars, to evaluate distances for gamma-selected pulsars. Distances of 35 gamma-selected pulsars are estimated, which could be tested by other distance measurement methods. The physical origin of the correlations may be also interesting for pulsar studies.

We discuss the effect of binary interactions on the tracers of star formation rate (including L1500, L2800, LHα, L[OII] and LFIR) at different metallicities (0.0001–0.03).

Chen et al. (2011) found that the durations (timescales) of the normal and abnormal modes of PSR B0329+54 follow a gamma distribution, and constrained the parameters of the distribution function. In this paper, we perform a further analysis on the relationship between the timescales of the two modes. The ratio between the durations of a normal mode and the succeeding abnormal mode is calculated for 54 such pairs. It is found that the cumulative distribution function (CDF) of the ratio is consistent with the CDF obtained by assuming random mode switching, suggesting that the two modes work independently.

The low stellar and gas mass fractions, low galaxy-wide star formation rates (relative to galactic dynamical times) and observations of rapid outflows from galaxies, all suggest that stars and active galactic nuclei violently alter the state of the interstellar and even inter-halo gas in galaxies. I argue that the low galaxy wide star formation rates are not the result of turbulent suppression of star formation on small scale, but rather the result of a balance between dynamical pressure and the force (or rate of momentum deposition) provided by stellar feedback, either in the form of radiation pressure or by supernovae. Galaxy scale winds can also be driven by feedback, either from stars or active galactic nuclei, although the exact mechanisms involved are still not well determined.

We investigate the curvature radiation from relativistic particles streaming along magnetic field lines and co-rotating with a pulsar. The co-rotation affects the trajectories of the particles and hence the emission properties, especially the polarization. For three density models in the form of core, cone and patches, we calculate the polarized emission at a given height and also the integrated emission for the whole open field line region, and try to explain the generation of circular polarization.

It is well known that shocks can heat molecular gas, but we are only starting to understand what the consequences might be for galaxy evolution. Observations are now revealing a growing number of galaxies undergoing phases of strong injection of kinetic energy through galaxy interactions or feedback from powerful AGN, which have bright line emission from shock-heated molecular gas that is likely powered by the dissipation of turbulent energy. These observations demonstrate that turbulence – now recognized as an important mechanism regulating star formation – may also be key in regulating galaxy growth. We report on our on-going efforts to quantify the role of molecular gas for the dissipation of kinetic energy through observations on two very different examples, the Antennae galaxy merger and the radio galaxy 3C326 N, a site of strong mechanical AGN feedback. Both galaxies show signatures of strong dissipation of kinetic energy through shocks. We will illustrate how key parameters of these processes like bulk and turbulent velocities, gas masses, and dissipation timescales can be measured with multi-wavelength data, and how this furthers our understanding of how galaxy evolution and star formation in galaxies depend on each other.

Anomalous X-ray pulsars (AXPs) are thought to be magnetars which are young isolated neutron stars with extremely strong magnetic fields of >1014 Gauss. Their tremendous magnetic fields inferred from the spin parameters provide a huge energy reservoir to power the observed X-ray emission. High-energy emission above 0.3 MeV has never been detected despite intensive search. Here, we present the possible Fermi Large Area Telescope (LAT) detection of γ-ray pulsations above 200 MeV from the AXP, 1E 2259+586, which puts the current theoretical models of γ-ray emission mechanisms of magnetars into challenge. We speculate that the high-energy γ-rays originate from the outer magnetosphere of the magnetar.

Although the “donut-like” obscuring molecular torus is often postulated to explain the type-1 and -2 dichotomy in AGNs, its physical origin is still unclear. We propose a plausible mechanism to explain the formation of the geometrically and optically thick torus, i.e. radiation-driven fountain. Using 3-D hydrodynamic simulations including radiative feedback from the central source, taking into account the X-ray heating and radiation pressure on the gas, we found that a vertical circulation of gas is generated in the central few to tens parsecs. Interaction between the non-steady outflows and inflows causes the formation of a geometrically thick torus with internal turbulent motion. As a result, the AGN is obscured for a wide range of solid angles. In a quasi-steady state, the opening angles for the column density toward a black hole < 1023 cm−2 are approximately ± 30° and ± 50° for AGNs with 10% and 1% Eddington luminosity, respectively. Mass inflows through the torus coexist with the outflow and internal turbulent motion, although the average mass accretion rate to the central parsec region is about ten times smaller than the accretion rate required to maintain the assumed AGN luminosity. This implies that relatively luminous AGN activity is intrinsically intermittent or that there are other mechanisms, such as stellar energy feedback, that enhance the mass accretion to the center.

We present results of an on-going program to measure AGN feedback in Seyfert galaxies using integral-field spectroscopy and adaptive optics at Keck Observatory and VLT. Our integral-field observations are revealing AGN-driven outflows of ionized gas in Seyfert galaxies. By resolving the inner 10–40 parsecs, we are successfully modeling them as biconical structures, in which the ionized gas first accelerates and then decelerates. The model parameters provide crucial information on the orientation, geometry and kinematics of the outflows, which is used to estimate mechanical feedback from the AGN: mass and kinetic energy transferred to the interstellar medium. Mass outflow rates can be 102–104 times greater than accretion rates, but in some cases, they are comparable to the estimated inflow rates to the central 10–25 pc, suggesting that the outflows may remove a considerable amount of the infalling gas before it reaches the accretion disk. In half of the AGN measured so far, the kinetic energy of the outflows appears sufficient to provide the eagerly-sought AGN feedback invoked to explain fundamental galaxy properties such as the MBH − σ* relation (0.5–5 Lbol). The other AGN, which lack powerful outflows, also have weaker and more compact radio jets.

Under the standard model extension (SME) framework, Lorentz invariance is tested in five binary pulsars: PSR J0737-3039, PSR B1534+12, PSR J1756-2251, PSR B1913+16 and PSR B2127+11C. By analyzing the advance of periastron, we obtain the constraints on a dimensionless combination of SME parameters that is sensitive to timing observations. The results imply no evidence for the break of Lorentz invariance at 10−10 level, one order of magnitude larger than previous estimation.

We have obtained ultraviolet spectra between 1150 and 1450 Å of four ultraviolet-bright, infrared-luminous starburst galaxies. Our selected sight-lines towards the starburst nuclei probe the conditions in the starburst-driven outflows. We detect outflowing gas with velocities of up to ∼900 km s−1. It is likely that the outflows are a major source of metal enrichment of the galaxies' halos. The mass outflow rates of several tens of M⊙ yr−1 are similar to the star-formation rates. The outflows may quench star formation and ultimately regulate the starburst.

We model the evolution of the magnetic fields of neutron stars as consisting of a long term power-law decay modulated by short term small amplitude oscillations. Our model predictions on the timing noise of neutron stars agree well with the observed statistical properties and correlations of normal radio pulsars. For individual pulsars our model can effectively reduce their timing residuals, thus offering the potential of more sensitive detections of gravitational waves with pulsar timing arrays. Finally our model can also re-produce their observed correlation and oscillations of second derivative of frenquency, as well as the “slow glitch” phenomenon.

We present astrometric results on two millisecond pulsars, PSR B1257+12 and PSR J1022+1001, as carried out through VLBI. For PSR B1257+12, a model-independent distance of 710−38+43 pc and proper motion of (μα = 46.44 ± 0.08 mas/yr, μδ=−84.87 ± 0.32 mas/yr) were obtained from 5 epochs of VLBA and 4 epochs of EVN observations, spanning about 2 years. The two dimensional proper motion of PSR J1022+1001 (μα~−10.13 mas/yr, μδ~16.89 mas/yr) was also estimated, using 3 epochs of EVN observations. Based on our results, the X-ray efficiency of PSR B1257+12 should be in the same range as other millisecond pulsars, and not as low as previously thought.

We detail the rich molecular story of NGC 1266, its serendipitous discovery within the ATLAS3D survey (Cappellari et al. 2011) and how it plays host to an AGN-driven molecular outflow, potentially quenching all of its star formation (SF) within the next 100 Myr. While major mergers appear to play a role in instigating outflows in other systems, deep imaging of NGC 1266 as well as stellar kinematic observations from SAURON, have failed to provide evidence that NGC 1266 has recently been involved in a major interaction. The molecular gas and the instantaneous SF tracers indicate that the current sites of star formation are located in a hypercompact disk within 200 pc of the nucleus (Fig. 1; SF rate ≈ 2 M⊙ yr−1). On the other hand, tracers of recent star formation, such as the Hβ absorption map from SAURON and stellar population analysis show that the young stars are distributed throughout a larger area of the galaxy than current star formation. As the AGN at the center of NGC 1266 continues to drive cold gas out of the galaxy, we expect star formation rates to decline as the star formation is ultimately quenched. Thus, NGC 1266 is in the midst of a key portion of its evolution and continued studies of this unique galaxy may help improve our understanding of how galaxies transition from the blue to the red sequence (Alatalo et al. 2011).

Energetic outflow from active galactic nuclei (AGNs) may play a critical role in galaxy evolution (e.g., Silk & Rees 1998). We present a velocity diagnostic for detecting gas outflow in the narrow-line region of Type-2 AGNs using line-of-sight velocity offsets of the [O iii] λ5007 and Hα emission lines with respect to the systemic velocity of stars in host galaxies (See Figure 1). We apply the diagnostics to nearby galaxies at 0.02 < z < 0.05, 3775 AGN-host and 907 star-forming galaxies as a comparison sample, which are selected from the Sloan Digital Sky Survey DR7. After obtaining a best-fit stellar population model for the continuum and a systemic velocity based on stellar lines, we subtract the stellar component to measure velocity offsets of each emission line. We find a sample of 169 AGN-host galaxies with outflow signatures, displaying a larger velocity shift of [O iii] than that of Hα, as expected in a decelerating outflow model (Komossa et al. 2008). We find that the offset velocity of [O iii] increases with Eddington ratio, suggesting that gas outflow depends on the energetics of AGN.

We performed a phase-resolved timing analysis of GRS 1915+105 in its ρ state and identify detailed ρ cycle evolution of frequency, amplitude and coherence of the low-frequency quasi-periodic oscillation (LFQPO). We combined our timing results with the spectral study by Neilsen et al. (2011) to do an elaborate contrast analysis. The results are naturally explained by tying the LFQPO to the corona.

As part of the Parkes Pulsar Timing Array (PPTA) project, frequent observations of 20 millisecond pulsars are made using the Parkes 64-m radio telescope. Variations in the mean position angle of the 20 millisecond pulsars can be studied by the PPTA data being recorded in full-polarization mode. We briefly discuss these results.

We present preliminary results of our integral field spectroscopy (IFS) observations to test whether AGN can suppress star formation in disc-dominated galaxies. We find a lower specific star formation rate and a different radial Hα profile for AGN than in the control sample.

We have carried out 1mm/3mm continuum and 12CO(2−1) line high resolution observations to identify the footprints of AGN feedback on 3C 236. The CO emission comes from a spatially resolved disk characterized by a regular rotating pattern. Within the limits imposed by the sensitivity and velocity coverage of our data, we do not detect any outflow signatures in the cold molecular gas. Re-inspection of optical and IR spectra, shows the presence of a previously unknown ionized gas outflow. The star-formation efficiency in 3C 236, is consistent with the value measured in normal galaxies, which follow the canonical Kennicutt-Schmidt law. This result, confirmed to hold in other young radio sources examined in this work, is in stark contrast with the factor of 10–50 lower SFE that has been claimed to characterize evolved powerful radio galaxies. The recent reactivation of the AGN in 3C 236 is a likely explanation for the early evolutionary status of its molecular disk.