The line-of-sight distribution of the gas in the inner 60 pc of the Galaxy

2MASS K_S band data of the inner 60 pc of the Galaxy are used to reconstruct the line-of-sight distances of the giant molecular clouds located in this region. Using the 2MASS H band image of the same region, two different populations of point sources are identified according to their flux ratio in the two bands. The population of blue point sources forms a homogeneous foreground that has to be subtracted before analyzing the K_S band image. The reconstruction is made using two basic assumptions: (i) an axis-symmetric stellar distribution in the region of interest and (ii) optically thick clouds with an area filling factor of ~1 that block all light of stars located behind them. Due to the reconstruction method, the relative distance between the different cloud complexes is a robust result, whereas it is not excluded that the absolute distance with respect to Sgr A* of structures located more than 10 pc in front of Sgr A* are understimated by up to a factor of 2. It is shown that all structures observed in the 1.2 mm continuum and in the CS(2-1) line are present in absorption. We place the 50 km s^-1 cloud complex close to, but in front of, Sgr A*. The 20 km s^-1 cloud complex is located in front of the 50 km s^-1 cloud complex and has a large LOS distance gradient along the direction of the galactic longitude. The bulk of the Circumnuclear Disk is not seen in absorption. This leads to an upper limit of the cloud sizes within the Circumnuclear Disk of ~0.06 pc.Comment: 12 pages with 17 figures. Accepted for publication in A&

The dynamics of the Circumnuclear Disk and its environment in the Galactic centre

We address the question of the dynamics in the inner 50 pc of the Galactic Centre. In a first step we investigate the cloud-cloud collision rate in the Circumnuclear Disk (CND) with the help of a three dimensional N-body code using gas particles that can have inelastic collisions. The CND might be a longer lived structure than previously assumed. The whole disk-like structure of the CND can thus survive for several million years. A realistic simulation of the CND shows the observed disk height structure. In a second step the environment of the CND is taken into account. Retrograde and prograde encounters of a cloud of several 10^4 M_solar falling onto an already existing nuclear disk using different energy loss rates per collision are simulated. The influence of the energy loss rate per collision on the evolution of the mass accretion and cloud collision rates is strongest for a prograde encounter. A composite data cube of two different snapshots of a prograde encounter together with the CND shows striking similarity with the observed Sgr A cloud complex. The current appearance of the Galactic Centre environment can thus be explained by at least two dynamically distinct features together with the CND. The current mass accretion rate within the CND ranges between 10^-3 and 10^-4 M_solar yr^-1. It can rise up to several 10^-2 M_solar yr^-1 during massive accretion events.Comment: 14 pages with 22 figures. Accepted for publication in A&

Bacteria isolated from Bengal cat (Felis catus × Prionailurus bengalensis) anal sac secretions produce volatile compounds potentially associated with animal signaling.

In social animals, scent secretions and marking behaviors play critical roles in communication, including intraspecific signals, such as identifying individuals and group membership, as well as interspecific signaling. Anal sacs are an important odor producing organ found across the carnivorans (species in the mammalian Order Carnivora). Secretions from the anal sac may be used as chemical signals by animals for behaviors ranging from defense to species recognition to signaling reproductive status. In addition, a recent study suggests that domestic cats utilize short-chain free fatty acids in anal sac secretions for individual recognition. The fermentation hypothesis is the idea that symbiotic microorganisms living in association with animals contribute to odor profiles used in chemical communication and that variation in these chemical signals reflects variation in the microbial community. Here we examine the fermentation hypothesis by characterizing volatile organic compounds (VOC) and bacteria isolated from anal sac secretions collected from a male Bengal cat (Felis catus × Prionailurus bengalensis), a cross between the domestic cat and the leopard cat. Both left and right anal sacs of a male Bengal cat were manually expressed (emptied) and collected. Half of the material was used to culture bacteria or to extract bacterial DNA and the other half was used for VOC analysis. DNA was extracted from the anal sac secretions and used for a 16S rRNA gene PCR amplification and sequencing based characterization of the microbial community. Additionally, some of the material was plated out in order to isolate bacterial colonies. Three taxa (Bacteroides fragilis, Tessaracoccus, and Finegoldia magna) were relatively abundant in the 16S rRNA gene sequence data and also isolated by culturing. Using Solid Phase Microextraction (SPME) gas chromatography-mass spectrometry (GC-MS), we tentatively identified 52 compounds from the Bengal cat anal sac secretions and 67 compounds from cultures of the three bacterial isolates chosen for further analysis. Among 67 compounds tentatively identified from bacterial isolates, 51 were also found in the anal sac secretion. We show that the bacterial community in the anal sac consists primarily of only a few abundant taxa and that isolates of these taxa produce numerous volatiles that are found in the combined anal sac volatile profile. Several of these volatiles are found in anal sac secretions from other carnivorans, and are also associated with known bacterial biosynthesis pathways. This is consistent with the fermentation hypothesis and the possibility that the anal sac is maintained at least in part to house bacteria that produce volatiles for the host

The Dynamics of Molecular Material Within 15 pcs of the Galactic Center

We report the results of a 5-field mosaic of the central 15pc of the Galaxy in the (1,1) and (2,2) lines of NH3. Two narrow filaments or streamers are seen running parallel to the Galactic plane. The southern streamer appears to carry gas directly toward the nuclear region from the 20 km/s cloud. The eastern streamer, which we will denote the molecular ridge, appears to be the denser part of the 50 km/s cloud which lies immediately east of the Sgr A East complex and extends in the south towards the 20 km/s cloud. This ridge of gas carries the kinematical signatures of interactions with Sgr A East as well as a SNR which lies south of the Galactic center. The bulk motion of the gas, the enhanced line widths, and the heating of the molecular material all suggest an active evolutionary phase for the gas immediately adjacent to the nucleus.Comment: 11 pages, 13 figures, to appear in The Astrophysical Journa

TriSol: a major upgrade of the TwinSol RNB facility

We report here on the recent upgrade of the TwinSol radioactive nuclear beam (RNB) facility at the University of Notre Dame. The new TriSol system includes a magnetic dipole to provide a second beamline and a third solenoid which acts to reduce the size of the radioactive beam on target.Comment: submitted to Nuclear Instruments and Methods

Mid-infrared Identification of 6 cm Radio Source Counterparts in the Extended Groth Strip

A new 6-cm survey of almost 0.6 square degrees to a limit of 0.55-mJy/beam (10-sigma) finds 37 isolated radio sources and 7 radio source pairs (not necessarily physical companions). IRAC counterparts are identified for at least 92% of the radio sources within the area of deep IRAC coverage, which includes 31 isolated sources and 6 pairs. This contrasts with an identification rate of <74% to R<23.95 in visible light. Eight of the IRAC galaxies have power law spectral energy distributions, implying that the mid-infrared emission comes from a powerful AGN. The remaining 26 IRAC galaxies show stellar emission in the mid-infrared, probably in most of these galaxies because the stellar emission is bright enough to outshine an underlying AGN. The infrared colors suggest that the majority of these galaxies are bulge-dominated and have redshifts between approximately 0.5 and 1.0. Visible spectra from the DEEP2 redshift survey, available for 11 galaxies, are consistent with this suggestion. The IRAC galaxies fall into two distinct groups in a color-magnitude diagram, one group (the "stripe") includes all the AGN. The other group (the "blue clump") has blue 3.6 to 8 micron colors and a small range of 8 micron magnitudes. This separation should be useful in classifying galaxies found in other radio surveys.Comment: Accepted by A

Predicting spectral features in galaxy spectra from broad-band photometry

We explore the prospects of predicting emission line features present in galaxy spectra given broad-band photometry alone. There is a general consent that colours, and spectral features, most notably the 4000 A break, can predict many properties of galaxies, including star formation rates and hence they could infer some of the line properties. We argue that these techniques have great prospects in helping us understand line emission in extragalactic objects and might speed up future galaxy redshift surveys if they are to target emission line objects only. We use two independent methods, Artifical Neural Neworks (based on the ANNz code) and Locally Weighted Regression (LWR), to retrieve correlations present in the colour N-dimensional space and to predict the equivalent widths present in the corresponding spectra. We also investigate how well it is possible to separate galaxies with and without lines from broad band photometry only. We find, unsurprisingly, that recombination lines can be well predicted by galaxy colours. However, among collisional lines some can and some cannot be predicted well from galaxy colours alone, without any further redshift information. We also use our techniques to estimate how much information contained in spectral diagnostic diagrams can be recovered from broad-band photometry alone. We find that it is possible to classify AGN and star formation objects relatively well using colours only. We suggest that this technique could be used to considerably improve redshift surveys such as the upcoming FMOS survey and the planned WFMOS survey.Comment: 10 pages 7 figures summitted to MNRA

A High-Resolution Survey of HI Absorption toward the Central 200 pc of the Galactic Center

We present an HI absorption survey of the central 250 pc of the Galaxy. Very Large Array (VLA) observations were made at 21 cm in the DnC and CnB configurations and have a resolution of ~15"(0.6 pc at the Galactic Center (GC) distance) and a velocity resolution of ~2.5 km/s. This study provides HI data with high spatial resolution, comparable with the many high resolution observations which have been made of GC sources over the past ten years. Here we present an overview of the HI absorption toward ~40 well-known continuum sources and a detailed comparison of the ionized, atomic and molecular components of the interstellar medium for the Sgr B, Radio Arc and Sgr C regions. In these well-known regions, the atomic gas appears to be closely correlated in both velocity and distribution to the ionized and molecular gas, indicating that it resides in photo-dissociation regions related to the HII regions in the GC. Toward the majority of the radio continuum sources, HI absorption by the 3-kpc arm is detected, constraining these sources to lie beyond a 5 kpc distance in the Galaxy.Comment: 59 pages, including 41 figures; accepted for publication in Astrophysical Journal Supplement Series in December 201