37,930 research outputs found
Near-infrared H2 and continuum survey of extended green objects. II. Complete census for the northern Galactic plane
We discuss 94 Extended Green Objects (EGOs) in the northern Galactic plane cataloged by Cyganowski et al., based on near-infrared narrow H2 (2.122 μm) and continuum observations from the United Kingdom Infrared Telescope. This data set is three times larger than the one in our previous study and is unbiased by preselection. As discussed in the previous paper, the morphologies of the 4.5 μm emission generally resemble those of the near-infrared continuum, but are different from those of the H2 emission. Of our sample, only 28% of EGOs with H2 emission show similar morphologies between 4.5 μm and H2 emission. These results suggest that the 4.5 μm emission mainly comes from scattered continuum from the embedded young stellar objects, and partially from H2 emission. About half of EGOs are associated with H2 outflows, if the H 2 outflow incompleteness is considered. The H2 outflow detection rate for EGOs with K-band detections (61%) is significantly higher than for those without K-band detections (36%). This difference may be due to the fact that both H2 and K-band emissions are associated with outflows, i.e., H2 emission and K-band continuum are associated with shocks and outflow cavities, respectively. We also compared the correlation between the H2 outflows and Class I 44 GHz methanol masers from the literature. The methanol masers can be located upstream or downstream of the H2 outflows and some bright H2 spots or outflows are not associated with methanol masers, suggesting that methanol masers and H 2 emission trace different excitation conditions. © 2013. The American Astronomical Society. All rights reserved.
Massive star formation and feedback in W49A: The source of our Galaxy's most luminous water maser outflow
We present high spatial resolution mid-IR images of the ring of UCHII regions
in W49A obtained at Gemini North, allowing us to identify the driving source of
its powerful H2O maser outflow. These data also confirm our previous report
that several radio sources in the ring are undetected in the mid-IR because
they are embedded deep inside the cloud core. We locate the source of the water
maser outflow at the position of the compact mid-IR peak of source G (source
G:IRS1). This IR source is not coincident with any identified compact radio
continuum source, but is coincident with a hot molecular core, so we propose
that G:IRS1 is a hot core driving an outflow analogous to the wide-angle
bipolar outflow in OMC-1. G:IRS1 is at the origin of a larger bipolar cavity
and CO outflow. The water maser outflow is orthogonal to the bipolar CO cavity,
so the masers probably reside near its waist in the cavity walls. Models of the
IR emission require a massive protostar of 45Msun, 3e5Lsun, and an effective
envelope accretion rate of 1e-3Msun/yr. Feedback from the central star could
potentially drive the H2O maser outflow, but it has insufficient radiative
momentum to have driven the large-scale CO outflow, requiring that this massive
star had an active accretion disk over the past 10^4 yr. Combined with the
spatialy resolved morphology in IR images, G:IRS1 in W49 provides compelling
evidence for a massive protostar that formed by accreting from a disk,
accompanied by a bipolar outflow.Comment: 14 pages, MNRAS accepte
Planetary Nebulae Detected in the Spitzer Space Telescope GLIMPSE 3D Legacy Survey
We used the data from the Spitzer Legacy Infrared Mid-Plane Survey
Extraordinaire (GLIMPSE) to investigate the mid-infrared (MIR) properties of
planetary nebulae (PNs) and PN candidates. In previous studies of GLIMPSE I& II
data, we have shown that these MIR data are very useful in distinguishing PNs
from other emission-line objects. In the present paper, we focus on the PNs in
the field of the GLIMPSE 3D survey, which has a more extensive latitude
coverage. We found a total of 90 Macquarie-AAO-Strasbourg (MASH) and MASH II
PNs and 101 known PNs to have visible MIR counterparts in the GLIMPSE 3D survey
area. The images and photometry of these PNs are presented. Combining the
derived IRAC photometry at 3.6, 4.5, 5.8, 8.0 um with the existing photometric
measurements from other infrared catalogs, we are able to construct spectral
energy distributions (SEDs) of these PNs. Among the most notable objects in
this survey is the PN M1-41, whose GLIMPSE 3D image reveals a large bipolar
structure of more than 3 arcmin in extent.Comment: 43 page3, 13 figures, Accepted for publication in Ap
The four spot time-of-flight laser anemometer
The newly constructed, four-spot anemometer was shown to perform as predicted. The new anemometer's measurement region has the required characteristics: wide acceptance angle and high spatial selectivity to permit measurements in turbulent, hostile environments
Solar Magnetic Feature Detection and Tracking for Space Weather Monitoring
We present an automated system for detecting, tracking, and cataloging
emerging active regions throughout their evolution and decay using SOHO
Michelson Doppler Interferometer (MDI) magnetograms. The SolarMonitor Active
Region Tracking (SMART) algorithm relies on consecutive image differencing to
remove both quiet-Sun and transient magnetic features, and region-growing
techniques to group flux concentrations into classifiable features. We
determine magnetic properties such as region size, total flux, flux imbalance,
flux emergence rate, Schrijver's R-value, R* (a modified version of R), and
Falconer's measurement of non-potentiality. A persistence algorithm is used to
associate developed active regions with emerging flux regions in previous
measurements, and to track regions beyond the limb through multiple solar
rotations. We find that the total number and area of magnetic regions on disk
vary with the sunspot cycle. While sunspot numbers are a proxy to the solar
magnetic field, SMART offers a direct diagnostic of the surface magnetic field
and its variation over timescale of hours to years. SMART will form the basis
of the active region extraction and tracking algorithm for the Heliophysics
Integrated Observatory (HELIO)
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