13 research outputs found
FIFI-LS FIR VIEW OF ORION: FINE STRUCTURE AND CO LINES
The Orion Nebula is the closest massive star forming region, which allows us to study its physical conditions at high spatial resolution. We used the far infrared integral-field spectrometer, FIFI-LS, on-board the airborne observatory SOFIA to study the Orion Nebula’s atomic and molecular gas.
We obtained large maps of fine structure and CO lines that span the nebula from the BN/KL-object to the bar. These maps allow us to study the conditions of the photon-dominated region and the interface to the molecular cloud.
A five-hundred-year-old violent explosion in the Orion Nebula has been stirring up the BN/KL region via wide-angled molecular outflows. We present maps of several high-J CO observations, allowing analysis of the heated molecular gas
HAWC+/SOFIA Polarimetry in L1688: Relative Orientation of Magnetic Field and Elongated Cloud Structure
We present a study of the relative orientation between the magnetic field and
elongated cloud structures for the Oph A and Oph E regions in
L1688 in the Ophiuchus molecular cloud. Combining inferred magnetic field
orientation from HAWC+ 154 m observations of polarized thermal emission
with column density maps created using Herschel submillimeter observations, we
find consistent perpendicular relative alignment at scales of pc
( at pc) using the histogram of relative orientations
(HRO) technique. This supports the conclusions of previous work using Planck
polarimetry and extends the results to higher column densities. Combining this
HAWC+ HRO analysis with a new Planck HRO analysis of L1688, the transition from
parallel to perpendicular alignment in L1688 is observed to occur at a
molecular hydrogen column density of approximately cm. This
value for the alignment transition column density agrees well with values found
for nearby clouds via previous studies using only Planck observations. Using
existing turbulent, magnetohydrodynamic simulations of molecular clouds formed
by colliding flows as a model for L1688, we conclude that the molecular
hydrogen volume density associated with this transition is approximately
cm. We discuss the limitations of our analysis, including
incomplete sampling of the dense regions in L1688 by HAWC+.Comment: To be published in Ap
The Twisted Magnetic Field of the Protobinary L483
We present H-band (1.65 μm) and SOFIA HAWC+ 154 μm polarization observations of the low-mass core L483. Our H-band observations reveal a magnetic field that is overwhelmingly in the E–W direction, which is approximately parallel to the bipolar outflow that is observed in scattered IR light and in single-dish 12CO observations. From our 154 μm data, we infer a ∼45° twist in the magnetic field within the inner 5″ (1000 au) of L483. We compare these new observations with published single-dish 350 μm polarimetry and find that the 10,000 au scale H-band data match the smaller-scale 350 μm data, indicating that the collapse of L483 is magnetically regulated on these larger scales. We also present high-resolution 1.3 mm Atacama Large Millimeter/submillimeter Array data of L483 that reveals it is a close binary star with a separation of 34 au. The plane of the binary of L483 is observed to be approximately parallel to the twisted field in the inner 1000 au. Comparing this result to the ∼1000 au protostellar envelope, we find that the envelope is roughly perpendicular to the 1000 au HAWC+ field. Using the data presented, we speculate that L483 initially formed as a wide binary and the companion star migrated to its current position, causing an extreme shift in angular momentum thereby producing the twisted magnetic field morphology observed. More observations are needed to further test this scenario
The magnetic field in the Milky Way filamentary bone G47
Funding: R.J.S. acknowledges funding from an STFC ERF (grant ST/N00485X/1).Star formation primarily occurs in filaments where magnetic fields are expected to be dynamically important. The largest and densest filaments trace the spiral structure within galaxies. Over a dozen of these dense (∼104 cm−3) and long (>10 pc) filaments have been found within the Milky Way, and they are often referred to as "bones." Until now, none of these bones has had its magnetic field resolved and mapped in its entirety. We introduce the SOFIA legacy project FIELDMAPS which has begun mapping ∼10 of these Milky Way bones using the HAWC+ instrument at 214 μm and 18′′.2 resolution. Here we present a first result from this survey on the ∼60 pc long bone G47. Contrary to some studies of dense filaments in the Galactic plane, we find that the magnetic field is often not perpendicular to the spine (i.e., the center line of the bone). Fields tend to be perpendicular in the densest areas of active star formation and more parallel or random in other areas. The average field is neither parallel nor perpendicular to the Galactic plane or the bone. The magnetic field strengths along the spine typically vary from ∼20 to ∼100 μG. Magnetic fields tend to be strong enough to suppress collapse along much of the bone, but for areas that are most active in star formation, the fields are notably less able to resist gravitational collapse.Peer reviewe
Early Planet Formation in Embedded Disks (eDisk). II. Limited Dust Settling and Prominent Snow Surfaces in the Edge-on Class I Disk IRAS 04302+2247
While dust disks around optically visible, Class II protostars are found to
be vertically thin, when and how dust settles to the midplane are unclear. As
part of the Atacama Large Millimeter/submillimeter Array (ALMA) large program,
Early Planet Formation in Embedded Disks, we analyze the edge-on, embedded,
Class I protostar IRAS 04302+2247, also nicknamed the ``Butterfly Star." With a
resolution of 0.05" (8~au), the 1.3 mm continuum shows an asymmetry along the
minor axis which is evidence of an optically thick and geometrically thick disk
viewed nearly edge-on. There is no evidence of rings and gaps, which could be
due to the lack of radial substructure or the highly inclined and optically
thick view. With 0.1" (16~au) resolution, we resolve the 2D snow surfaces,
i.e., the boundary region between freeze-out and sublimation, for CO
=2--1, CO =2--1, CO =2--1, CO
=--, and SO =--, and constrain the CO
midplane snow line to au. We find Keplerian rotation around a
protostar of using CO. Through forward
ray-tracing using RADMC-3D, we find that the dust scale height is au
at a radius of 100~au from the central star and is comparable to the gas
pressure scale height. The results suggest that the dust of this Class~I source
has yet to vertically settle significantly.Comment: 33 pages, 21 figures. Accepted for publication in ApJ as one of the
first-look papers of the eDisk ALMA Large Progra
Early Planet Formation in Embedded Disks (eDisk). VII. Keplerian Disk, Disk Substructure, and Accretion Streamers in the Class 0 Protostar IRAS 16544-1604 in CB 68
We present observations of the Class 0 protostar IRAS 16544-1604 in CB 68
from the ''Early Planet Formation in Embedded Disks (eDisk)'' ALMA Large
program. The ALMA observations target continuum and lines at 1.3-mm with an
angular resolution of 5 au. The continuum image reveals a dusty
protostellar disk with a radius of 30 au seen close to edge-on, and
asymmetric structures both along the major and minor axes. While the asymmetry
along the minor axis can be interpreted as the effect of the dust flaring, the
asymmetry along the major axis comes from a real non-axisymmetric structure.
The CO image cubes clearly show the gas in the disk that follows a
Keplerian rotation pattern around a 0.14 central protostar.
Furthermore, there are 1500 au-scale streamer-like features of gas
connecting from North-East, North-North-West, and North-West to the disk, as
well as the bending outflow as seen in the CO (2-1) emission. At the
apparent landing point of NE streamer, there are SO (6-5) and SiO (5-4)
emission detected. The spatial and velocity structure of NE streamer can be
interpreted as a free-falling gas with a conserved specific angular momentum,
and the detection of the SO and SiO emission at the tip of the streamer implies
presence of accretion shocks. Our eDisk observations have unveiled that the
Class 0 protostar in CB 68 has a Keplerian rotating disk with flaring and
non-axisymmetric structure associated with accretion streamers and outflows.Comment: 30 pages, 24 figures, accepted for publication in The Astrophysical
Journal as one of the first-look papers of the eDisk ALMA Large Progra
Early Planet Formation in Embedded Disks (eDisk). I. Overview of the Program and First Results
We present an overview of the Large Program, ``Early Planet Formation in
Embedded Disks (eDisk)'', conducted with the Atacama Large
Millimeter/submillimeter Array (ALMA). The ubiquitous detections of
substructures, particularly rings and gaps, in protoplanetary disks around T
Tauri stars raise the possibility that at least some planet formation may have
already started during the embedded stages of star formation. In order to
address exactly how and when planet formation is initiated, the program focuses
on searching for substructures in disks around 12 Class 0 and 7 Class I
protostars in nearby (200 pc) star-forming regions through 1.3 mm continuum
observations at a resolution of au (0.04"). The initial results show
that the continuum emission, mostly arising from dust disks around the sample
protostars, has relatively few distinctive substructures, such as rings and
spirals, in marked contrast to Class II disks. The dramatic difference may
suggest that substructures quickly develop in disks when the systems evolve
from protostars to Class II sources or alternatively that high optical depth of
the continuum emission could obscure internal structures. Kinematic information
obtained through CO isotopologue lines and other lines reveals the presence of
Keplerian disks around protostars, providing us with crucial physical
parameters, in particular, the dynamical mass of the central protostars. We
describe the background of the eDisk program, the sample selection and their
ALMA observations, the data reduction, and also highlight representative
first-look results.Comment: This is a publication of a series of eDisk ALMA large program
first-look paper
FIFI-LS FIR VIEW OF ORION: FINE STRUCTURE AND CO LINES
The Orion Nebula is the closest massive star forming region, which allows us to study its physical conditions at high spatial resolution. We used the far infrared integral-field spectrometer, FIFI-LS, on-board the airborne observatory SOFIA to study the Orion Nebula’s atomic and molecular gas.
We obtained large maps of fine structure and CO lines that span the nebula from the BN/KL-object to the bar. These maps allow us to study the conditions of the photon-dominated region and the interface to the molecular cloud.
A five-hundred-year-old violent explosion in the Orion Nebula has been stirring up the BN/KL region via wide-angled molecular outflows. We present maps of several high-J CO observations, allowing analysis of the heated molecular gas
The magnetic field in the Milky Way filamentary bone G47
Star formation primarily occurs in filaments where magnetic fields are expected to be dynamically important. The largest and densest filaments trace the spiral structure within galaxies. Over a dozen of these dense (∼104 cm−3) and long (>10 pc) filaments have been found within the Milky Way, and they are often referred to as "bones." Until now, none of these bones has had its magnetic field resolved and mapped in its entirety. We introduce the SOFIA legacy project FIELDMAPS which has begun mapping ∼10 of these Milky Way bones using the HAWC+ instrument at 214 μm and 18′′.2 resolution. Here we present a first result from this survey on the ∼60 pc long bone G47. Contrary to some studies of dense filaments in the Galactic plane, we find that the magnetic field is often not perpendicular to the spine (i.e., the center line of the bone). Fields tend to be perpendicular in the densest areas of active star formation and more parallel or random in other areas. The average field is neither parallel nor perpendicular to the Galactic plane or the bone. The magnetic field strengths along the spine typically vary from ∼20 to ∼100 μG. Magnetic fields tend to be strong enough to suppress collapse along much of the bone, but for areas that are most active in star formation, the fields are notably less able to resist gravitational collapse