26 research outputs found
IRS Scan-mapping of the Wasp-waist Nebula (IRAS 16253â2429). I. Derivation of Shock Conditions from H_2 Emission and Discovery of 11.3 ÎŒm PAH Absorption
The outflow driven by the Class 0 protostar, IRAS 16253â2429, is associated with bipolar cavities visible in scattered mid-infrared light, which we refer to as the Wasp-Waist Nebula. InfraRed Spectometer (IRS) scan mapping with the Spitzer Space Telescope of a ~1' Ă 2' area centered on the protostar was carried out. The outflow is imaged in six pure rotational (0-0 S(2) through 0-0 S(7)) H_2 lines, revealing a distinct, S-shaped morphology in all maps. A source map in the 11.3 ÎŒm polycyclic aromatic hydrocarbon (PAH) feature is presented in which the protostellar envelope appears in absorption. This is the first detection of absorption in the 11.3 ÎŒm PAH feature. Spatially resolved excitation analysis of positions in the blue- and redshifted outflow lobes, with extinction-corrections determined from archival Spitzer 8 ÎŒm imaging, shows remarkably constant temperatures of ~1000 K in the shocked gas. The radiated luminosity in the observed H_2 transitions is found to be 1.94 ± 0.05 Ă 10^(â5) L_â in the redshifted lobe and 1.86 ± 0.04 Ă 10^(â5) L_â in the blueshifted lobe. These values are comparable to the mechanical luminosity of the flow. By contrast, the mass of hot (T ~ 1000 K) H_2 gas is 7.95 ± 0.19 Ă 10^(â7) M_â in the redshifted lobe and 5.78 ± 0.17 Ă 10^(â7) M_â in the blueshifted lobe. This is just a tiny fraction, of order 10^(â3), of the gas in the cold (30 K), swept-up gas mass derived from millimeter CO observations. The H_2 ortho/para ratio of 3:1 found at all mapped points in this flow suggests previous passages of shocks through the gas. Comparison of the H_2 data with detailed shock models of Wilgenbus et al. shows the emitting gas is passing through Jump (J-type) shocks. Pre-shock densities of 10^4 cm^(â3)†n _H †10^5 cm^(â3) are inferred for the redshifted lobe and n _H †10^3 cm^(â3) for the blueshifted lobe. Shock velocities are 5 km s^(â1) †v_s †10 km s^(â1) for the redshifted gas and v_s = 10 km s^(â1) for the blueshifted gas. Initial transverse (to the shock) magnetic field strengths for the redshifted lobe are in the range 10-32 ÎŒG, and just 3 ÎŒG for the blueshifted lobe. A cookbook for using the CUBISM contributed software for IRS spectral mapping data is presented in the Appendix
Protostellar Outflows in L1340
We have searched the L1340 A, B, and C clouds for shocks from protostellar outflows using the H_2 2.122 ÎŒm near-infrared line as a shock tracer. Substantial outflow activity has been found in each of the three regions of the cloud (L1340 A, L1340 B, and L1340 C). We find 42 distinct shock complexes (16 in L1340 A, 11 in L1340 B, and 15 in L1340 C). We were able to link 17 of those shock complexes into 12 distinct outflows and identify candidate source stars for each. We examine the properties (A_V, T_(bol), and L_(bol)) of the source protostars and compare them to the properties of the general population of Class 0/I and flat spectral energy distribution protostars and find that there is an indication, albeit at low statistical significance, that the outflow-driving protostars are drawn from a population with lower A_V, higher L_(bol), and lower T_(bol) than the general population of protostars
Protostellar Outflows in L1340
We have searched the L1340 A, B, and C clouds for shocks from protostellar outflows using the H_2 2.122 ÎŒm near-infrared line as a shock tracer. Substantial outflow activity has been found in each of the three regions of the cloud (L1340 A, L1340 B, and L1340 C). We find 42 distinct shock complexes (16 in L1340 A, 11 in L1340 B, and 15 in L1340 C). We were able to link 17 of those shock complexes into 12 distinct outflows and identify candidate source stars for each. We examine the properties (A_V, T_(bol), and L_(bol)) of the source protostars and compare them to the properties of the general population of Class 0/I and flat spectral energy distribution protostars and find that there is an indication, albeit at low statistical significance, that the outflow-driving protostars are drawn from a population with lower A_V, higher L_(bol), and lower T_(bol) than the general population of protostars
A Mid-Infrared Study of the Class 0 Cluster in LDN 1448
We present ground-based mid-infrared observations of Class 0 protostars in
LDN 1448. Of the five known protostars in this cloud, we detected two, L1448N:A
and L1448C, at 12.5, 17.9, 20.8, and 24.5 microns, and a third, L1448 IRS 2, at
24.5 microns. We present high-resolution images of the detected sources, and
photometry or upper limits for all five Class 0 sources in this cloud. With
these data, we are able to augment existing spectral energy distributions
(SEDs) for all five objects and place them on an evolutionary status diagram.Comment: Accepted by the Astronomical Journal; 26 pages, 9 figure
Giant Molecular Outflows Powered by Protostars in L1448
We present sensitive, large-scale maps of the CO J=1-0 emission of the L1448
dark cloud. These maps were acquired using the On-The-Fly capability of the
NRAO 12-meter telescope. CO outflow activity is seen in L1448 on parsec-scales
for the first time. Careful comparison of the spatial and velocity distribution
of our high-velocity CO maps with previously published optical and
near-infrared images and spectra has led to the identification of six distinct
CO outflows. We show the direct link between the heretofore unknown, giant,
highly-collimated, protostellar molecular outflows and their previously
discovered, distant optical manifestations. The outflows traced by our CO
mapping generally reach the projected cloud boundaries. Integrated intensity
maps over narrow velocity intervals indicate there is significant overlap of
blue- and red-shifted gas, suggesting the outflows are highly inclined with
respect to the line-of-sight, although the individual outflow position angles
are significantly different. The velocity channel maps also show that the
outflows dominate the CO line cores as well as the high-velocity wings. The
magnitude of the combined flow momenta, as well as the combined kinetic energy
of the flows, are sufficient to disperse the 50 solar mass NH3 cores in which
the protostars are currently forming, although some question remains as to the
exact processes involved in redirecting the directionality of the outflow
momenta to effect the complete dispersal of the parent cloud.Comment: 11 pages, 9 figures, to be published in the Astronomical Journa
Life in 2.5D: Animal Movement in the Trees
The complex, interconnected, and non-contiguous nature of canopy environments present unique cognitive, locomotor, and sensory challenges to their animal inhabitants. Animal movement through forest canopies is constrained; unlike most aquatic or aerial habitats, the three-dimensional space of a forest canopy is not fully realized or available to the animals within it. Determining how the unique constraints of arboreal habitats shape the ecology and evolution of canopy-dwelling animals is key to fully understanding forest ecosystems. With emerging technologies, there is now the opportunity to quantify and map tree connectivity, and to embed the fine-scale horizontal and vertical position of moving animals into these networks of branching pathways. Integrating detailed multi-dimensional habitat structure and animal movement data will enable us to see the world from the perspective of an arboreal animal. This synthesis will shed light on fundamental aspects of arboreal animalsâ cognition and ecology, including how they navigate landscapes of risk and reward and weigh energetic trade-offs, as well as how their environment shapes their spatial cognition and their social dynamics
Near-infrared and Millimeter-wavelength Observations of Mol 160: A Massive Young Protostellar Core
We have discovered two compact sources of shocked H2 2.12-micron emission
coincident with Mol 160 (IRAS 23385+6053), a massive star-forming core thought
to be a precursor to an ultracompact HII region. The 2.12-micron sources lie
within 2" (0.05 pc) of a millimeter-wavelength continuum peak where the column
density is >= 10e24 cm. We estimate that the ratio of molecular hydrogen
luminosity to bolometric luminosity is > 0.2%, indicating a high ratio of
mechanical to radiant luminosity. CS J=2-1 and HCO J=1-0 observations with
CARMA indicate that the protostellar molecular core has a peculiar velocity of
~ 2 km s with respect to its parent molecular cloud. We also observed 95
GHz CH3OH J=8$-7 Class I maser emission from several locations within the core.
Comparison with previous observations of 44-GHz CH3OH maser emission shows the
maser sources have a high mean ratio of 95-GHz to 44-GHz intensity. Our
observations strengthen the case that Mol 160 (IRAS 23385+6053) is a rapidly
accreting massive protostellar system in a very early phase of its evolution.Comment: 47 pages, 8 figures, 2 tables, accepted for publication in ApJ, 7 Dec
201