MUSE discovers perpendicular arcs in the inner filament of Cen A

Evidence of AGN interaction with the IGM is observed in some galaxies and many cool core clusters. Radio jets are suspected to dig large cavities into the surrounding gas. In most cases, very large optical filaments are seen around the central galaxy. The origin of these filaments is still not understood. Star-forming regions are sometimes observed inside the filaments and are interpreted as evidence of positive feedback. Cen A is a nearby galaxy with huge optical filaments aligned with the AGN radio-jet direction. We searched for line ratio variations along the filaments, kinematic evidence of shock-broadend line widths, and large-scale dynamical structures. We observed a 1'x1' region around the inner filament of Cen A with MUSE on the VLT during Science Verification. The brightest lines detected are the Halpha, [NII], [OIII] and [SII]. MUSE shows that the filaments are made of clumpy structures inside a more diffuse medium aligned with the radio-jet axis. We find evidence of shocked shells surrounding the star-forming clumps from the line profiles, suggesting that the star formation is induced by shocks. The clump line ratios are best explained by a composite of shocks and star formation illuminated by a radiation cone from the AGN. We also report a previously undetected large arc-like structure: three streams running perpendicular to the main filament; they are kinematically, morphologically, and excitationally distinct. The clear difference in the excitation of the arcs and clumps suggests that the arcs are very likely located outside of the radiation cone and match the position of the filament only in projection. The three arcs are most consistent with neutral material swept along by a backflow of the jet plasma from the AGN outburst that is ionised through a diffuse radiation field with a low-ionisation parameter that continues to excite gas away from the radiation cone.Comment: 14 Pages (4 paper, 10 appendices), 12 Figures (3 paper, 9 appendicies). Accepted for publication by A&

Cold Gas in Galaxy Cluster Cores

We present a survey of 73 galaxy groups and clusters aimed at determining the role played by the cold gas in the feedback process. We use optical Integral Field Spectroscopy from the VIsible Multi Object Spectrograph in conjunction with high spatial resolution X-ray observations from the Chandra X-ray Observatory and extensive multi-wavelength observations to study the interactions of the cold gas with the Intra Cluster Medium and the Brightest Cluster Galaxy. The wealth of information provided by these observations has allowed us to study the kinematic structure of the cold gas in the largest sample of cluster cores to date. We use this information to shed new light three key questions i) Are all line emitting systems highly disturbed? ii) What role does the Brightest Cluster Galaxy play in the cooling of gas from the ICM? iii) What role does the cold gas play in the feedback process and what is its relationship to the fueling of the AGN?. The analysis of the full survey immediately suggests that the line emitting gas in the majority of cluster cores isn’t highly disturbed. While several clusters do show a disturbed Hα morphology (13/73) the majority appeared uniform and quiescent (45/73). Similarly the velocity structure of the ionised gas within most systems also appears to be very ordered and interestingly appears decoupled from the stellar kinematics of the brightest cluster galaxy. Several of the more disturbed systems do show evidence of an interaction with another cluster member, however, this is not common to all disturbed systems. One of the most interesting discoveries to come out of the sample analysis is the identification of a small sub sample of objects which show an offset between the brightest cluster galaxy and the bulk of the ionised gas. Comparison to X-ray observations indicates that the cluster core is spatially coincident with the ionised gas emission and not the galaxy. These objects provided an opportunity to study the role played by the BCG in the cooling of gas from the ICM. The kinematics of these objects suggests that these offsets should be transient and short lived. Despite this we identify a substantial mass of cold molecular gas (∼109 M⊙ ) associated with the offset emission, and not the BCG, for one object. This mass is consistent with the upper limit of the cooling during the lifetime of the offset suggesting that the cooling continues to occur in the core despite being offset from the BCG. This result clearly indicates that while the BCG may typically reside at the centre of most clusters it is not required for cooling gas to condense from the ICM. Finally, we address the ordered velocity structure of the ionised gas in BCG in much greater detail. As a pilot project we study the kinematics of Hydra-A using detailed multi-wavelength observations and identify the presence of a disk of cold gas which has an axis of rotation parallel to the axis along which the AGN is inflating cavities into the ICM. Comparison to the energetics of the cavities suggests that the mass of cold gas in the disk is sufcient to fuel a future outburst of comparable magnitude. Noting the similar velocity structure in many of the clusters in our sample we apply a similar analysis to the full sample. We use kinemetry and determine that ≈62% of the sample have ionised gas kinematics which are consistent with a rotating disk. A linear trend is identified between the peak rotational amplitude of these disks and the linewidth of CO observations which suggests that the large mass of cold molecular gas present in the cores of clusters shares the kinematic structure of the ionised gas. Finally, we compare the axis of rotation of all disks with radio and X-ray observations and identify a clear alignment between the jets/cavities and the disks axis of rotation. The prevalence of these disks and their alignment with the axis along which the AGN is injecting mechanical energy into the ICM clearly suggests that they play an important role in the feedback process and provides a link between the gas cooling on kpc scales and the fueling of the black hole at the centre of the BCG

Environmental issues associated with the Department of Defense Base Realignment and Closure (BRAC) program.

The purpose of this paper is to take a comprehensive look at the environmental restoration issues surrounding the implementation of the Department of Defense's Base Realignment and Closure (BRAC) Program. Environmental problems at DoD sites present some unique challenges because environmental priorities must be integrated with the national security missions of each DoD Service. Still environmental hazards must be dealt with before the military bases can be transferred of sold back to the local communities. It is also important for the Federal Government to present a unified picture to the public of a government committed to environmental protection and restoration at it's own facilities at least to the same extent that it is committed to environmental protection at private sites. This paper will examine the statutes and regulations surrounding the environmental cleanups. It will also research the mechanism by which the DoD can best achieve this end and the resources at its disposal for restorations of hazardous/toxic wastes sites at its facilities in the continental U.S. and overseashttp://archive.org/details/environmentaliss00ham

Star formation efficiency along the radio jet in Centaurus A

Centaurus A is the most nearby powerful AGN, widely studied at all wavelengths. Molecular gas has been found in the halo at a distance of ~20 kpc from the galaxy centre, associated with HI shells. The molecular gas lies inside some IR and UV bright star-forming filaments that have recently been observed in the direction of the radio jets. These archival data show that there is dust and very weak star formation on scales of hundreds of parsecs. On top of analysing combined archival data, we have performed searches of HCN(1-0) and HCO+(1-0) emission with ATCA at the interaction of the northern filaments and the HI shell of Cen A. Measuring the dense gas is another indicator of star formation efficiency inside the filaments. However, we only derived upper limits of 1.6x10^3 K.km/s.pc^2 at 3 sigma in the synthesised beam of 3.1". We also compared the CO masses with the SFR estimates in order to measure a star formation efficiency. Using a standard conversion factor leads to long depletion times (7 Gyr). We then corrected the mass estimates from metallicity effect by using gas-to-dust mass ratio as a proxy. From MUSE data, we estimated the metallicity spread (0.4-0.8 Zsun) in the filament, corresponding to gas-to-dust ratios of ~200-400. The CO/H2 conversion ratio is corrected for low metallicity by a factor between 1.4 and 3.2. Such a low-metallicity correction leads to even more massive clouds with higher depletion times (16 Gyr). We finally present ALMA observations that detect 3 unresolved CO(2-1) clumps of siz

Inefficient jet-induced star formation in Centaurus A:High resolution ALMA observations of the northern filaments

NGC 5128 is one of the best targets to study AGN-feedback in the local Universe. At 13.5 kpc from the galaxy, optical filaments with recent star formation lie along the radio-jet direction. It is a testbed region for positive feedback (jet-induced star formation). APEX revealed strong CO emission in star-forming regions but also in regions with no detected tracers of star formation. When observed, star formation appears to be inefficient compared to the Kennicutt-Schmidt relation. We used ALMA to map the 12CO(1-0) emission all along the filaments at 1.3"~ 23.8 pc resolution. The CO emission is clumpy and distributed in two main structures: (i) the Horseshoe complex, outside the HI cloud, where gas is mostly excited by shocks and no star formation is observed; (ii) the Vertical filament, at the edge of the HI shell, which is a region of moderate star formation. We identified 140 molecular clouds. A statistical study reveals that they have very similar physical properties that in the inner Milky Way. However, the range of radius available with the present observations does not enable to investigate whether the clouds follow the Larson relation or not. The large virial parameter of the clouds suggests that gravity is not dominant. Finally, the total energy injection in the filaments is of the same order as in the inner part of the Milky Way. The strong CO emission detected in the filaments is an indication that the energy injected by the jet acts positively in the formation of dense molecular gas. The relatively high virial parameter of the molecular clouds suggests that the injected kinetic energy is too strong for star formation to be efficient. This is particularly the case in the Horseshoe complex where the virial parameter is the largest and where strong CO is detected with no associated star formation. This is the first evidence of inefficient AGN positive feedback

Three dimensional tracking of a wide-ranging marine predator: flight heights and vulnerability to offshore wind farms

1. A large increase in offshore wind turbine capacity is anticipated in the next decade, raising concerns about possible adverse impacts on birds as a result of collision risk. Birds’ flight heights greatly influence this risk yet height estimates are currently available only using methods such as radar or ship-based observations over limited areas. 2. Bird-borne data-loggers have the potential to provide improved estimates of collision risk and here, we use data from GPS-loggers and barometric pressure-loggers to track the three-dimensional movements of northern gannets rearing chicks at a large colony in SE Scotland (Bass Rock), located < 50km from several major wind farm developments with recent planning consent. We estimate the foraging ranges and densities of birds at sea, their flight heights during different activities and the spatial variation in height during trips. We then use these data in collision-risk models to explore how the use of different methods to determine flight height affects the predicted risk of birds colliding with turbines. 3. Gannets foraged in and around planned wind farm sites. The probability of flying at collision- risk height was low during commuting between colonies and foraging areas (median height 12m) but was greater during periods of active foraging (median height 27m), and we estimate that ~1500 breeding adults from Bass Rock could be killed by collision with wind turbines at two planned sites in the Firth of Forth region each year. This is up to 12 times potential mortality predicted using other available flight height estimates. 4. Synthesis & Applications: The use of conventional flight height estimation techniques resulted in large underestimates of the numbers of birds at risk of colliding with wind turbines. Hence we recommend using GPS and barometric tracking to derive activity-specific and spatially-explicit flight heights and collision risks. Our predictions of potential mortality approached levels at which long-term population viability could be threatened, highlighting a need for further data to refine estimates of collision risks and sustainable mortality thresholds. We also advocate raising the minimum permitted clearance of turbine blades at sites with high potential collision risk from 22m 51 to 30m above sea level

Star formation efficiency along the radio jet in Centaurus A

Centaurus A is the most nearby powerful AGN, widely studied at all wavelengths. Molecular gas has been found in the halo at a distance of ~20 kpc from the galaxy centre, associated with HI shells. The molecular gas lies inside some IR and UV bright star-forming filaments that have recently been observed in the direction of the radio jets. These archival data show that there is dust and very weak star formation on scales of hundreds of parsecs. On top of analysing combined archival data, we have performed searches of HCN(1-0) and HCO+(1-0) emission with ATCA at the interaction of the northern filaments and the HI shell of Cen A. Measuring the dense gas is another indicator of star formation efficiency inside the filaments. However, we only derived upper limits of 1.6x10^3 K.km/s.pc^2 at 3 sigma in the synthesised beam of 3.1". We also compared the CO masses with the SFR estimates in order to measure a star formation efficiency. Using a standard conversion factor leads to long depletion times (7 Gyr). We then corrected the mass estimates from metallicity effect by using gas-to-dust mass ratio as a proxy. From MUSE data, we estimated the metallicity spread (0.4-0.8 Zsun) in the filament, corresponding to gas-to-dust ratios of ~200-400. The CO/H2 conversion ratio is corrected for low metallicity by a factor between 1.4 and 3.2. Such a low-metallicity correction leads to even more massive clouds with higher depletion times (16 Gyr). We finally present ALMA observations that detect 3 unresolved CO(2-1) clumps of size <37x21 pc and masses around 10^4 Msun. The velocity width of the CO emission line is ~10 km/s, leading to a rather high virial parameter. This is a hint of a turbulent gas probably powered by kinetic energy injection from the AGN jet/wind and leading to molecular gas reservoir not forming star efficiently.Comment: New version taking into account private conversations about v1; accepted to A&

Correlation between Tick Density and Pathogen Endemicity, New Hampshire

To assess the endemicity of tick-borne pathogens in New Hampshire, we surveyed adult tick vectors. Pathogens were more prevalent in areas of high tick density, suggesting a correlation between tick establishment and pathogen endemicity. Infection rates in ticks correlated with disease frequency in humans

Incidence, scaling relations and physical conditions of ionized gas outflows in MaNGA

In this work, we investigate the strength and impact of ionised gas outflows within $z \sim 0.04$ MaNGA galaxies. We find evidence for outflows in 322 galaxies ($12\%$ of the analysed line-emitting sample), 185 of which show evidence for AGN activity. Most outflows are centrally concentrated with a spatial extent that scales sublinearly with $R_{\rm e}$. The incidence of outflows is enhanced at higher masses, central surface densities and deeper gravitational potentials, as well as at higher SFR and AGN luminosity. We quantify strong correlations between mass outflow rates and the mechanical drivers of the outflow of the form $\dot{M}_{\rm out} \propto \rm SFR^{0.97}$ and $\dot{M}_{\rm out} \propto L_{\rm AGN}^{0.55}$. We derive a master scaling relation describing the mass outflow rate of ionised gas as a function of $M_{\star}$, SFR, $R_{\rm e}$ and $L_{\rm AGN}$. Most of the observed winds are anticipated to act as galactic fountains, with the fraction of galaxies with escaping winds increasing with decreasing potential well depth. We further investigate the physical properties of the outflowing gas finding evidence for enhanced attenuation in the outflow, possibly due to metal-enriched winds, and higher excitation compared to the gas in the galactic disk. Given that the majority of previous studies have focused on more extreme systems with higher SFRs and/or more luminous AGN, our study provides a unique view of the non-gravitational gaseous motions within `typical' galaxies in the low-redshift Universe, where low-luminosity AGN and star formation contribute jointly to the observed outflow phenomenology.Comment: Accepted for publication in MNRAS, 27 pages, Fig 7 & 8 for scaling wind strength with drivers, Fig 10 for master scalin