The Effect of Corotation on the Radial Gradient of Metallicity of Spiral Galaxies

The corotation radius in a spiral galaxy is the radius where the spiral pattern speed has the same velocity of the rotation curve. By compiling results from the literature for 20 spiral galaxies we verified a strong correlation between the radius of the minima or inflections of the metallicity distribution and the corotation radius.Comment: 3 pages, 1 figur

CO observations and investigation of triggered star formation towards N10 infrared bubble and surroundings

We studied the environment of the dust bubble N10 in molecular emission. Infrared bubbles, first detected by the GLIMPSE survey at 8.0 $\mu$m, are ideal regions to investigate the effect of the expansion of the HII region on its surroundings eventual triggered star formation at its borders. In this work, we present a multi-wavelength study of N10. This bubble is especially interesting as infrared studies of the young stellar content suggest a scenario of ongoing star formation, possibly triggered, on the edge of the HII region. We carried out observations of $^{12}$CO(1-0) and $^{13}$CO(1-0) emission at PMO 13.7-m towards N10. We also analyzed the IR and sub-mm emission on this region and compare those different tracers to obtain a detailed view of the interaction between the expanding HII region and the molecular gas. We also estimated the parameters of the denser cold dust condensation and of the ionized gas inside the shell. Bright CO emission was detected and two molecular clumps were identified, from which we have derived physical parameters. We also estimate the parameters for the densest cold dust condensation and for the ionized gas inside the shell. The comparison between the dynamical age of this region and the fragmentation time scale favors the "Radiation-Driven Implosion" mechanism of star formation. N10 reveals to be specially interesting case with gas structures in a narrow frontier between HII region and surrounding molecular material, and with a range of ages of YSOs situated in region indicating triggered star formation.Comment: Version 2 - Submmited to ApJ (under review

First optical images of circumstellar dust surrounding the debris disk candidate HD 32297

Near-infrared imaging with the Hubble Space Telescope recently revealed a circumstellar dust disk around the A star HD 32297. Dust scattered light is detected as far as 400 AU radius and the linear morphology is consistent with a disk ~10 degrees away from an edge-on orientation. Here we present the first optical images that show the dust scattered light morphology from 560 to 1680 AU radius. The position angle of the putative disk midplane diverges by 31 degrees and the color of dust scattering is most likely blue. We associate HD 32297 with a wall of interstellar gas and the enigmatic region south of the Taurus molecular cloud. We propose that the extreme asymmetries and blue disk color originate from a collision with a clump of interstellar material as HD 32297 moves southward, and discuss evidence consistent with an age of 30 Myr or younger.Comment: 5 pages; Accepted for publication in ApJ Letter

HI aperture synthesis and optical observations of the pair of galaxies NGC 6907 and 6908

NGC 6908, a S0 galaxy situated in direction of NGC 6907, was only recently recognized as a distinct galaxy, instead of only a part of NGC 6907. We present 21 cm radio synthesis observations obtained with the GMRT and optical images and spectroscopy obtained with the Gemini North telescope of this pair of interacting galaxies. From the radio observations we obtained the velocity field and the HI column density map of the whole region containing the NGC 6907/8 pair, and by means of the Gemini multi-object spectroscopy we obtained high quality photometric images and $5 {\AA}$ resolution spectra sampling the two galaxies. By comparing the rotation curve of NGC 6907 obtained from the two opposite sides around the main kinematic axis, we were able to distinguish the normal rotational velocity field from the velocity components produced by the interaction between the two galaxies. Taking into account the rotational velocity of NGC 6907 and the velocity derived from the absorption lines for NGC 6908, we verified that the relative velocity between these systems is lower than 60 km s$^{-1}$. The emission lines observed in the direction of NGC 6908, not typical of S0 galaxies, have the same velocity expected for the NGC 6907 rotation curve. Some of them, superimposed on the absorption profiles, which reinforces the idea that they were not formed in NGC 6908. Finally, the HI profile exhibits details of the interaction, showing three components: one for NGC 6908, another for the excited gas in the NGC 6907 disk and a last one for the gas with higher relative velocities left behind NGC 6908 by dynamical friction, used to estimate the time when the interaction started in $(3.4 \pm 0.6)\times10^7$ years ago.Comment: 11 pages, 5 tables, 13 figures. Corrected typos. Accepted for publication in MNRAS. The definitive version will be available at http://www.blackwell-synergy.co

An Automated Machine-Learning Approach for Road Pothole Detection Using Smartphone Sensor Data.

Road surface monitoring and maintenance are essential for driving comfort, transport safety and preserving infrastructure integrity. Traditional road condition monitoring is regularly conducted by specially designed instrumented vehicles, which requires time and money and is only able to cover a limited proportion of the road network. In light of the ubiquitous use of smartphones, this paper proposes an automatic pothole detection system utilizing the built-in vibration sensors and global positioning system receivers in smartphones. We collected road condition data in a city using dedicated vehicles and smartphones with a purpose-built mobile application designed for this study. A series of processing methods were applied to the collected data, and features from different frequency domains were extracted, along with various machine-learning classifiers. The results indicated that features from the time and frequency domains outperformed other features for identifying potholes. Among the classifiers tested, the Random Forest method exhibited the best classification performance for potholes, with a precision of 88.5% and recall of 75%. Finally, we validated the proposed method using datasets generated from different road types and examined its universality and robustness

On the Reported Death of the MACHO Era

We present radial velocity measurements of four wide halo binary candidates from the sample in Chaname & Gould (2004; CG04) which, to date, is the only sample containing a large number of such candidates. The four candidates that we have observed have projected separations >0.1 pc, and include the two widest binaries from the sample, with separations of 0.45 and 1.1 pc. We confirm that three of the four CG04 candidates are genuine, including the one with the largest separation. The fourth candidate, however, is spurious at the 5-sigma level. In the light of these measurements we re-examine the implications for MACHO models of the Galactic halo. Our analysis casts doubt on what MACHO constraints can be drawn from the existing sample of wide halo binaries.Comment: 6 Pages, 4 Figures, Accepted for MNRAS Letter

Use of waveform lidar and hyperspectral sensors to assess selected spatial and structural patterns associated with recent and repeat disturbance and the abundance of sugar maple (Acer saccharum Marsh.) in a temperate mixed hardwood and conifer forest.

Abstract Waveform lidar imagery was acquired on September 26, 1999 over the Bartlett Experimental Forest (BEF) in New Hampshire (USA) using NASA\u27s Laser Vegetation Imaging Sensor (LVIS). This flight occurred 20 months after an ice storm damaged millions of hectares of forestland in northeastern North America. Lidar measurements of the amplitude and intensity of ground energy returns appeared to readily detect areas of moderate to severe ice storm damage associated with the worst damage. Southern through eastern aspects on side slopes were particularly susceptible to higher levels of damage, in large part overlapping tracts of forest that had suffered the highest levels of wind damage from the 1938 hurricane and containing the highest levels of sugar maple basal area and biomass. The levels of sugar maple abundance were determined through analysis of the 1997 Airborne Visible/Infrared Imaging Spectrometer (AVIRIS) high resolution spectral imagery and inventory of USFS Northern Research Station field plots. We found a relationship between field measurements of stem volume losses and the LVIS metric of mean canopy height (r2 = 0.66; root mean square errors = 5.7 m3/ha, p \u3c 0.0001) in areas that had been subjected to moderate-to-severe ice storm damage, accurately documenting the short-term outcome of a single disturbance event

On the difference between type E and A OH/IR stars

The observed SEDs of a sample of 60 OH/IR stars are fitted using a radiative transfer model of a dusty envelope. Among the whole sample, 21 stars have reliable phase-lag distances while the others have less accurate distances. L*-P,Mlr-P and Mlr-L* relations have been plotted for these stars. It is found that type E (with emission feature at 10um and type A (with absorption feature at 10um) OH/IR stars have different L*-P and Mlr-L* relations while both of them follow a single Mlr-P relation. The type E stars are proven to be located in the area without large scale dense interstellar medium while the type A stars are located probably in dense interstellar medium. It is argued here that this may indicate the two types of OH/IR stars have different chemical composition or zero age main sequence mass and so evolve in different ways. This conclusion has reinforced the argument by Chen et al.(2001) who reached a similar conclusion from the galactic distribution of about 1000 OH/IR stars with the IRAS low-resolution spectra (LRS).Comment: 6 pages, 9 figures, 2 table