Josh Walawender | Subaru Telescope, NAOJ (original) (raw)
Papers by Josh Walawender
Astrophysical Journal, 2010
The Bolocam Galactic Plane Survey (BGPS) data for a six square degree region of the Galactic plan... more The Bolocam Galactic Plane Survey (BGPS) data for a six square degree region of the Galactic plane containing the Galactic center is analyzed and compared to infrared and radio continuum data. The BGPS 1.
Revista Mexicana De Astronomia Y Astrofisica, 2010
In this work we study Herbig-Haro objects located in the region around the head of the cometary g... more In this work we study Herbig-Haro objects located in the region around the head of the cometary globule CG 30. Two sets of optical images are presented. The first set was obtained with the 3.5 m New Technology Telescope in 1995 in three emission lines: Hα, S IIλλ6731,6716Å and [O II]λ3729Å. The second set is an Hα image of the CG 30/31/38 complex obtained in 2006 with the 8 m Subaru telescope. A proper motion study of the HH objects in the region was performed using the Hα images from both epochs. Due to the high resolution of our images we were able to, for the first time, resolve the HH 120 object into ten knots and measure proper motions for some of them. We discover several new HH objects and a large bipolar jet, HH 950, emerging from the head of CG 30. We suggest that two previously known submillimeter sources are the driving sources for the HH 120 and HH 950 flows.
Astronomical Journal, 2005
We report the detection of several new circumstellar disks seen in silhouette against background ... more We report the detection of several new circumstellar disks seen in silhouette against background nebular light in the outskirts of the Orion nebula and the neighboring H ii region M43. These were detected as part of our Hα survey of Orion with the Advanced Camera for Surveys on-board the Hubble Space Telescope. Several of the disks show bipolar reflection nebulae, microjets, or pronounced temporal variability of their central stars. The relatively large fraction of bipolar reflection nebulae or microjets in our sample may be a selection effect caused by the faint nebular background far from the Trapezium. Two disks in our sample are large and particularly noteworthy: A nearly edge-on disk, d216-0939, is located several arcminutes northwest of M43 and resembles the famous HH 30 disk/jet system in Taurus. It drives the 0.15 pc long bipolar outflow HH 667, and exhibits a remarkable asymmetric reflection nebula caused by the tilt of the flared disk. With a diameter of ∼2. ′′ 6 (1200 AU), d216-0939 is as large as the giant edge-on silhouette disk d114-426 in the core of the Orion Nebula. The large disk d253-1536 is located in a binary system embedded within an externally-ionized giant proplyd in M43. The disk exhibits distortions which we attribute to tidal interactions with the companion star. The bipolar jet HH 668 emerges from the proplyd ionization front in a direction orthogonal to the disk, and can be traced to the young star embedded within it. A bow shock lies 54 ′′ south of this binary system along the outflow axis. Proper motions over a 1.4 yr baseline confirm that these emission knots are indeed moving away from d253-1536, with speeds as high as ∼330 km s −1 in the HH 668 microjet, and slower motion farther from the star.
Astronomical Journal, 2005
We present Hubble Space Telescope Advanced Camera for Surveys images of the giant proplyd 181À826... more We present Hubble Space Telescope Advanced Camera for Surveys images of the giant proplyd 181À826 in the southern Orion Nebula. This object exhibits a variety of known proplyd properties-an optically visible central star, a silhouette disk, a bright proplyd ionization front, and a bipolar microjet emerging along the disk axis that powers a larger Herbig-Haro flow. The proplyd ionization front is remarkable because of its large size (a radius of about 800 AU) and because of its corrugated structure consisting of a set of coaxial rings with the same orientation as the embedded silhouette disk. The rings are centered on the disk /jet axis, and we discuss possible mechanisms for their formation. The silhouette disk has an outer radius of about 160 AU, and its axis is inclined by an angle of about 60 with respect to our line of sight. A prominent reflection nebula protrudes along the disk axis toward the south, marking the base of the approaching outflow, and a faint knot on the north side of the disk indicates that the nebula is bipolar. Fabry-Pérot images reveal a high-velocity blueshifted jet with a mass-loss rate of about 10 À8 M yr À1 emerging along the disk axis. It has a velocity (corrected for the outflow inclination angle) of about 160 km s À1 and can be traced for about 1 0 toward the south. A chain of three lower velocity blueshifted bow shocks, collectively known as HH 540, extend several arcminutes south of 181À826 along the same axis, tracing a largescale outflow powered by this jet.
![Research paper thumbnail of And in the Darkness Bind Them: Equatorial Rings, B[e] Supergiants, and the Waists of Bipolar Nebulae](https://attachments.academia-assets.com/31967896/thumbnails/1.jpg)
](Astronomical Journal, 2007
We report the discovery of two new circumstellar ring nebulae in the western Carina Nebula, and w... more We report the discovery of two new circumstellar ring nebulae in the western Carina Nebula, and we discuss their significance in stellar evolution. The brighter of the two new objects, SBW1, resembles a lidless staring eye and encircles a B1.5 Iab supergiant. Although seen in Carina, its luminosity class and radial velocity imply a larger distance of ∼7 kpc in the far Carina arm. At that distance its size and shape are nearly identical to the equatorial ring around SN1987A, but SBW1's low N abundance indicates that the ring was excreted without its star passing through a red supergiant phase. The fainter object, SBW2, is a more distorted ring, is N-rich, and is peculiar in that its central star seems to be invisible. We discuss the implications of these two new nebulae in context with other circumstellar rings such as those around SN1987A, Sher 25, HD 168625, RY Scuti, WeBo1, SuWt2, and others. The ring bearers fall into two groups: Five rings surround hot supergiants, and it is striking that all except for the one known binary are carbon copies of the ring around SN1987A. We propose a link between these B supergiant rings and B[e] supergiants, where the large spatially-resolved rings derive from the same material that would have given rise to emission lines during the earlier B[e] phase, when it was much closer to the star. The remaining four rings surround evolved intermediate-mass stars; all members of this ring fellowship are close binaries, hinting that binary interactions govern the forging of such rings. Two-thirds of our sample are found in or near giant H ii regions. We estimate that there may be several thousand more dark rings in the Galaxy, but we are scarcely aware of their existence -either because they are only illuminated in precious few circumstances or because of selection effects. For intermediate-mass stars, these rings might be the pre-existing equatorial density enhancements invoked to bind the waists of bipolar nebulae.
We propose to search for new irradiated jets and protostellar outflows, shocks, protoplanetary di... more We propose to search for new irradiated jets and protostellar outflows, shocks, protoplanetary disks seen in silhouette (dark proplyds), and photo-ablating disks (bright proplyds), in the Carina Nebula with narrow-band filters and the MOSAIC camera on the CTIO 4 meter. Pilot observations obtained last December have demonstrated that this region contains a rich harvest of disks and outflows. A complete MOSAIC survey is needed to determine their population. The Carina Nebula is the most massive star forming region with the largest population of early O stars in which circumstellar disks, irradiated jets, and protostellar jets (Herbig-Haro objects) have so far been found. This is because Carina is much closer to us than other clusters with comparable populations of massive stars. These observations will extend our understanding of low-mass star formation, outflow production and impacts on the surrounding medium, and protoplanetary disk survival - to regions where the most massive stars are born. A detailed investigation of the Carina Nebula will provide a fundamental stepping stone to understanding how these processes operate in luminous H II region complexes in our Galaxy, the LMC and SMC, and in other galaxies.
We propose to probe the line emission from nearby star forming regions in the 5 to 37 micron spec... more We propose to probe the line emission from nearby star forming regions in the 5 to 37 micron spectral range using the slit-scan mode of IRS. Our goals are: [1] Measure the fluxes produced by the pure rotational lines of molecular hydrogen and other spectral features in the 5 to 38 micrometer region from the surroundings of 4 well-studied and nearby outflow sources. [2] Trace the intermediate velocity (2 to 30 km/sec) shocks in outflow regions. Such emission is predicted by models in which high velocity motions traced by optical and near-IR emission lines (Herbig-Haro objects) accelerate molecular outflows and degrade into turbulent motions. We will obtain slit-scan maps in the LL and SL modes of IRS of arc-minute scale regions surrounding HH 211, HH212, L1448c and, NGC 2071. By observing these four sources, we will compare the mid-IR emission lines produced by regions supporting various levels of star formation activity ranging from the birth of isolated single stars, to small groups, to rich clusters containing over 100 YSOs and stars as massive as 8 to 10 Solar masses.
Astronomical Journal, 2009
We have used deep optical (Hα and [S ii]) and near-IR (H 2 and K S ) images and catalogs of proto... more We have used deep optical (Hα and [S ii]) and near-IR (H 2 and K S ) images and catalogs of protostars based on optical and infrared data to follow up our previous observations and examine the protostellar outflow population in the Barnard 1 (B1) dark cloud. The deep images presented here link shocks at the low extinction periphery of the cloud to an outflow system that bisects the confused core of B1. In addition, we find that a deeply embedded infrared shock, previously identified as a protostar, is likely the impact of a flow on a submillimeter clump. In all, we detail nine outflow systems in this cloud, eight of which have clearly identified source protostars.
Astrophysical Journal Supplement Series, 2010
We present a catalog of 8358 sources extracted from images produced by the Bolocam Galactic Plane... more We present a catalog of 8358 sources extracted from images produced by the Bolocam Galactic Plane Survey (BGPS). The BGPS is a survey of the millimeter dust continuum emission from the northern Galactic plane. The catalog sources are extracted using a custom algorithm, Bolocat, which was designed specifically to identify and characterize objects in the large-area maps generated from the Bolocam instrument. The catalog products are designed to facilitate follow-up observations of these relatively unstudied objects. The catalog is 98% complete from 0.4 Jy to 60 Jy over all object sizes for which the survey is sensitive (< 3.5 ′ ). We find that the sources extracted can best be described as molecular clumps -large dense regions in molecular clouds linked to cluster formation. We find the flux density distribution of sources follows a power law with dN/dS ∝ S −2.4±0.1 and that the mean Galactic latitude for sources is significantly below the midplane: b = (−0.095 ± 0.001) • .
Astronomical Journal, 2006
We present a survey of shocks and outflows in the Chamaeleon I star-forming complex using Hα, [S ... more We present a survey of shocks and outflows in the Chamaeleon I star-forming complex using Hα, [S II], and SDSS i' images obtained from the ground, an i' image obtained with the Hubble Space Telescope, and 4.5 μm images obtained with the Infrared Array Camera (IRAC) on the Spitzer Space Telescope. We find new Herbig-Haro (HH) objects and extensions to the previously cataloged shocks that trace parts of at least 20 distinct outflows from young stars. Some HH objects mark the presence of giant outflows, the largest of which is powered by Cha-MMS1 and associated with HH 49/50 near the Ced 110 region. Other large flows are powered by Cha-MMS2 in the Ced 112 region and the IRN in the Ced 111 region. Although some shocks exhibit infrared emission in the IRAC bands, most notably HH 49/50 (the ``tornado''), most outflows in the Cha I clouds are not detected in the Spitzer IRAC bands. This result is consistent with the general lack of extensive 2.12 μm H2 emission from Cha I.
We present the Bolocam Galactic Plane Survey (BGPS), a 1.1 mm continuum survey at 33 effective re... more We present the Bolocam Galactic Plane Survey (BGPS), a 1.1 mm continuum survey at 33 effective resolution of 170 square degrees of the Galactic Plane visible from the northern hemisphere. The BGPS is one of the first large area, systematic surveys of the Galactic Plane in the millimeter continuum without arXiv:1011.0691v1 [astro-ph.GA] 2 Nov 2010 -2pre-selected targets. The survey is contiguous over the range −10.5 ≤ l ≤ 90.5, |b| ≤ 0.5. Towards the Cygnus X spiral arm, the coverage was flared to |b| ≤ 1.5 for 75.5 ≤ l ≤ 87.5. In addition, cross-cuts to |b| ≤ 1.5 were made at l = 3, 15, 30 and 31. The total area of this section is 133 square degrees. With the exception of the increase in latitude, no pre-selection criteria were applied to the coverage in this region. In addition to the contiguous region, four targeted regions in the outer Galaxy were observed: IC1396 (9 square degrees, 97.5 ≤ l ≤ 100.5, 2.25 ≤ b ≤ 5.25), a region towards the Perseus Arm (4 square degrees centered on l = 111, b = 0 near NGC7538), W3/4/5 (18 square degrees, 132.5 ≤ l ≤ 138.5) and Gem OB1 (6 square degrees, 187.5 ≤ l ≤ 193.5).
Astronomical Journal, 2004
... A NEW GIANT HERBIG-HARO FLOW IN L1451 Josh Walawender, 1,2 John Bally, 1,2 Bo Reipurth, 3 and... more ... A NEW GIANT HERBIG-HARO FLOW IN L1451 Josh Walawender, 1,2 John Bally, 1,2 Bo Reipurth, 3 and Colin Aspin 4 ... The flow is driven by the Class I protostar IRAS 03235+3004 embedded in a bright-rimmed, sharp-edged cometary cloud facing northeast. ...
Astronomical Journal, 2005
... Josh Walawender, 1, 2 John Bally, 1, 2 Helen Kirk, 3, 4 and Doug Johnstone 3, 4 ... To minimi... more ... Josh Walawender, 1, 2 John Bally, 1, 2 Helen Kirk, 3, 4 and Doug Johnstone 3, 4 ... To minimize negative &#x27;&#x27;bowling&#x27;&#x27; around bright sources, all points with values outside of Æ5 times the mean noise per pixel were set to those values before convolution. ...
Astronomical Journal, 2009
New observations of protostellar outflows associated with young stars in two of Orion's outlying ... more New observations of protostellar outflows associated with young stars in two of Orion's outlying cometary clouds, L1622 and L1634, are presented. The Hα surface brightness of the bright rims are used to argue that both clouds are located at a distance of about 400 pc in the interior of the Orion superbubble where they are illuminated by Orion's massive stars. Spitzer IRAC and MIPS images reveal 28 candidate young stellar objects (YSOs). Combined with the 14 spectroscopically confirmed T Tauri stars, there are at least 34 YSOs in L1622. Narrow-band images have led to the identification of about a dozen shock complexes in L1622. At least six belong to a highly collimated externally irradiated, bipolar jet, HH 963, that is powered by a low-luminosity Class II YSO located outside the projected edge of the L1622 dark cloud. However, the sources of most shocks remain unclear. The Spitzer/IRAC images reveal a compact, highly obscured, S-symmetric outflow brightest in the 4.5 μm images. A faint [S II] counter part, HH 962, is associated with the western end of this flow which appears to be powered by an obscured source in the L1622 cloud interior. The currently identified sample of YSOs implies a star formation efficiency of about 4% for L1622. The L1634 cloud contains nine YSOs and three outflows, including the well known HH 240/241 system. A new flow, HH 979, is powered by the embedded YSO IRS7 in L1634 and crosses the eastern lobe of the HH 240 outflow. Spitzer/IRAC images show 4.5 μm emission indicating molecular shocks from the Herbig-Haro objects closest to IRS 7. A YSO embedded in a condensation located 5' north of HH 240/241 is identified in the Spitzer images. This source drives an irradiated outflow, HH 980, whose lobes emerge into the ionized environment of the Orion-Eridanus superbubble interior. The star formation efficiency of L1634 is estimated to be about 3%.
Astronomical Journal, 2010
A population of 11 faint, collimated jets has been discovered in the northern part of the L1641 c... more A population of 11 faint, collimated jets has been discovered in the northern part of the L1641 cloud in the region of HH 1/2, HH 34, and the L1641-N cluster. These jets were missed in previous imaging surveys on account of their weak emission, and they were discovered only on deep exposures with the Subaru 8m telescope. With these new faint jets, the number of HH flows within the area surveyed has doubled. This suggests that collimated jets from young stars may be more common than assumed so far. It is noteworthy that all of the jets are associated with optically visible stars with r-magnitudes ranging from 13.8 to 22.0. The driving sources of jets in regions flooded by ultraviolet radiation from nearby OB stars are known to be excavated by photo-ionization, and in three cases remnant Hα emission envelopes are found associated with the sources, although the more benign environment in the region observed here, about 10 pc distant from the Orion Nebula Cluster, makes the optical visibility of all these sources rather surprising. Such faint jets from visible stars represent either the final vestiges of the outflow phenomenon, or they are triggered by disturbances of the remnant disks, possibly initiated by the orbital evolution of binaries that spiral in to form close binaries. Among the known Hα emission stars within the region surveyed, 8% are found to be associated with jets.
Astronomical Journal, 2006
The Circinus giant molecular cloud is a little explored region that deserves closer study owing t... more The Circinus giant molecular cloud is a little explored region that deserves closer study owing to the many signs of vigorous low-mass star formation in the form of Hα emission stars, Herbig-Haro objects, molecular outflows, and embedded sources. The western part of the cloud complex has a filamentary structure with numerous cavities, indicating the effect of powerful molecular outflows. It is likely that the current strong star formation activity was triggered by a supernova explosion. Our present limited knowledge about this region is summarized, and several particularly interesting sources are discussed.
Astrophysical Journal Supplement Series, 2011
We present the Bolocam Galactic Plane Survey (BGPS), a 1.1 mm continuum survey at 33'' effective ... more We present the Bolocam Galactic Plane Survey (BGPS), a 1.1 mm continuum survey at 33'' effective resolution of 170 deg2 of the Galactic Plane visible from the northern hemisphere. The BGPS is one of the first large area, systematic surveys of the Galactic Plane in the millimeter continuum without pre-selected targets. The survey is contiguous over the range -10.5 <= l <= 90.5, |b| <= 0.5. Toward the Cygnus X spiral arm, the coverage was flared to |b| <= 1.5 for 75.5 <= l <= 87.5. In addition, cross-cuts to |b| <= 1.5 were made at l= 3, 15, 30, and 31. The total area of this section is 133 deg2. With the exception of the increase in latitude, no pre-selection criteria were applied to the coverage in this region. In addition to the contiguous region, four targeted regions in the outer Galaxy were observed: IC1396 (9 deg2, 97.5 <= l <= 100.5, 2.25 <= b <= 5.25), a region toward the Perseus Arm (4 deg2 centered on l = 111, b = 0 near NGC 7538), W3/4/5 (18 deg2, 132.5 <= l <= 138.5), and Gem OB1 (6 deg2, 187.5 <= l <= 193.5). The survey has detected approximately 8400 clumps over the entire area to a limiting non-uniform 1σ noise level in the range 11-53 mJy beam-1 in the inner Galaxy. The BGPS source catalog is presented in a previously published companion paper. This paper details the survey observations and data reduction methods for the images. We discuss in detail the determination of astrometric and flux density calibration uncertainties and compare our results to the literature. Data processing algorithms that separate astronomical signals from time-variable atmospheric fluctuations in the data timestream are presented. These algorithms reproduce the structure of the astronomical sky over a limited range of angular scales and produce artifacts in the vicinity of bright sources. Based on simulations, we find that extended emission on scales larger than about 5farcm9 is nearly completely attenuated (>90%) and the linear scale at which the attenuation reaches 50% is 3farcm8. Comparison with other millimeter-wave data sets implies a possible systematic offset in flux calibration, for which no cause has been discovered. This presentation serves as a companion and guide to the public data release (http://irsa.ipac.caltech.edu/Missions/bolocam.html) through NASA's Infrared Processing and Analysis Center (IPAC) Infrared Science Archive (IRSA). New data releases will be provided through IPAC-IRSA with any future improvements in the reduction. The BGPS provides a complementary long-wavelength spectral band for the ongoing ATLASGAL and Herschel-SPIRE surveys, and an important database and context for imminent observations with SCUBA-2 and ALMA.
Astrophysical Journal, 2010
We present the 1.1 millimeter Bolocam Galactic Plane Survey (BGPS) observations of the Gemini OB1... more We present the 1.1 millimeter Bolocam Galactic Plane Survey (BGPS) observations of the Gemini OB1 molecular cloud complex, and targeted NH 3 observations of the BGPS sources. When paired with molecular spectroscopy of a dense gas tracer, millimeter observations yield physical properties such as masses, radii, mean densities, kinetic temperatures and line widths. We detect 34 distinct BGPS sources above 5σ = 0.37 Jy beam −1 with corresponding 5σ detections in the NH 3 (1,1) transition. Eight of the objects show water maser emission (20%). We find a mean millimeter source FWHM of 1.12 pc, and a mean gas kinetic temperature of 20 K for the sample of 34 BGPS sources with detections in the NH 3 (1,1) line. The observed NH 3 line widths are dominated by non-thermal motions, typically found to be a few times the thermal sound speed expected for the derived kinetic temperature. We calculate the mass for each source from the millimeter flux assuming the sources are isothermal and find a mean isothermal mass within a 120 ′′ aperture of 230 ± 180 M ⊙ . We find a total mass of 8,400 M ⊙ for all BGPS sources in the Gemini OB1 molecular cloud, representing 6.5% of the cloud mass. By comparing the millimeter isothermal mass to the virial mass within a radius equal to the mm source size calculated from the NH 3 line widths, we find a mean virial parameter (M vir /M iso ) of 1.0±0.9 for the sample. We find mean values for the distributions of column densities of 1.0 × 10 22 cm −2 for H 2 , and 3.0 × 10 14 cm −2 for NH 3 , giving a mean NH 3 abundance of 3.0 × 10 −8 relative to H 2 . We find volume-averaged densities on the order of 10 3 − 10 4 cm −3 . The sizes and densities suggest that in the Gem OB 1 region the BGPS is detecting the clumps from which stellar clusters form, rather than smaller, higher density cores where single stars or small multiple systems form.
Astrophysical Journal, 2010
The Bolocam Galactic Plane Survey (BGPS) data for a six square degree region of the Galactic plan... more The Bolocam Galactic Plane Survey (BGPS) data for a six square degree region of the Galactic plane containing the Galactic center is analyzed and compared to infrared and radio continuum data. The BGPS 1.
Revista Mexicana De Astronomia Y Astrofisica, 2010
In this work we study Herbig-Haro objects located in the region around the head of the cometary g... more In this work we study Herbig-Haro objects located in the region around the head of the cometary globule CG 30. Two sets of optical images are presented. The first set was obtained with the 3.5 m New Technology Telescope in 1995 in three emission lines: Hα, S IIλλ6731,6716Å and [O II]λ3729Å. The second set is an Hα image of the CG 30/31/38 complex obtained in 2006 with the 8 m Subaru telescope. A proper motion study of the HH objects in the region was performed using the Hα images from both epochs. Due to the high resolution of our images we were able to, for the first time, resolve the HH 120 object into ten knots and measure proper motions for some of them. We discover several new HH objects and a large bipolar jet, HH 950, emerging from the head of CG 30. We suggest that two previously known submillimeter sources are the driving sources for the HH 120 and HH 950 flows.
Astronomical Journal, 2005
We report the detection of several new circumstellar disks seen in silhouette against background ... more We report the detection of several new circumstellar disks seen in silhouette against background nebular light in the outskirts of the Orion nebula and the neighboring H ii region M43. These were detected as part of our Hα survey of Orion with the Advanced Camera for Surveys on-board the Hubble Space Telescope. Several of the disks show bipolar reflection nebulae, microjets, or pronounced temporal variability of their central stars. The relatively large fraction of bipolar reflection nebulae or microjets in our sample may be a selection effect caused by the faint nebular background far from the Trapezium. Two disks in our sample are large and particularly noteworthy: A nearly edge-on disk, d216-0939, is located several arcminutes northwest of M43 and resembles the famous HH 30 disk/jet system in Taurus. It drives the 0.15 pc long bipolar outflow HH 667, and exhibits a remarkable asymmetric reflection nebula caused by the tilt of the flared disk. With a diameter of ∼2. ′′ 6 (1200 AU), d216-0939 is as large as the giant edge-on silhouette disk d114-426 in the core of the Orion Nebula. The large disk d253-1536 is located in a binary system embedded within an externally-ionized giant proplyd in M43. The disk exhibits distortions which we attribute to tidal interactions with the companion star. The bipolar jet HH 668 emerges from the proplyd ionization front in a direction orthogonal to the disk, and can be traced to the young star embedded within it. A bow shock lies 54 ′′ south of this binary system along the outflow axis. Proper motions over a 1.4 yr baseline confirm that these emission knots are indeed moving away from d253-1536, with speeds as high as ∼330 km s −1 in the HH 668 microjet, and slower motion farther from the star.
Astronomical Journal, 2005
We present Hubble Space Telescope Advanced Camera for Surveys images of the giant proplyd 181À826... more We present Hubble Space Telescope Advanced Camera for Surveys images of the giant proplyd 181À826 in the southern Orion Nebula. This object exhibits a variety of known proplyd properties-an optically visible central star, a silhouette disk, a bright proplyd ionization front, and a bipolar microjet emerging along the disk axis that powers a larger Herbig-Haro flow. The proplyd ionization front is remarkable because of its large size (a radius of about 800 AU) and because of its corrugated structure consisting of a set of coaxial rings with the same orientation as the embedded silhouette disk. The rings are centered on the disk /jet axis, and we discuss possible mechanisms for their formation. The silhouette disk has an outer radius of about 160 AU, and its axis is inclined by an angle of about 60 with respect to our line of sight. A prominent reflection nebula protrudes along the disk axis toward the south, marking the base of the approaching outflow, and a faint knot on the north side of the disk indicates that the nebula is bipolar. Fabry-Pérot images reveal a high-velocity blueshifted jet with a mass-loss rate of about 10 À8 M yr À1 emerging along the disk axis. It has a velocity (corrected for the outflow inclination angle) of about 160 km s À1 and can be traced for about 1 0 toward the south. A chain of three lower velocity blueshifted bow shocks, collectively known as HH 540, extend several arcminutes south of 181À826 along the same axis, tracing a largescale outflow powered by this jet.
Astronomical Journal, 2007
We report the discovery of two new circumstellar ring nebulae in the western Carina Nebula, and w... more We report the discovery of two new circumstellar ring nebulae in the western Carina Nebula, and we discuss their significance in stellar evolution. The brighter of the two new objects, SBW1, resembles a lidless staring eye and encircles a B1.5 Iab supergiant. Although seen in Carina, its luminosity class and radial velocity imply a larger distance of ∼7 kpc in the far Carina arm. At that distance its size and shape are nearly identical to the equatorial ring around SN1987A, but SBW1's low N abundance indicates that the ring was excreted without its star passing through a red supergiant phase. The fainter object, SBW2, is a more distorted ring, is N-rich, and is peculiar in that its central star seems to be invisible. We discuss the implications of these two new nebulae in context with other circumstellar rings such as those around SN1987A, Sher 25, HD 168625, RY Scuti, WeBo1, SuWt2, and others. The ring bearers fall into two groups: Five rings surround hot supergiants, and it is striking that all except for the one known binary are carbon copies of the ring around SN1987A. We propose a link between these B supergiant rings and B[e] supergiants, where the large spatially-resolved rings derive from the same material that would have given rise to emission lines during the earlier B[e] phase, when it was much closer to the star. The remaining four rings surround evolved intermediate-mass stars; all members of this ring fellowship are close binaries, hinting that binary interactions govern the forging of such rings. Two-thirds of our sample are found in or near giant H ii regions. We estimate that there may be several thousand more dark rings in the Galaxy, but we are scarcely aware of their existence -either because they are only illuminated in precious few circumstances or because of selection effects. For intermediate-mass stars, these rings might be the pre-existing equatorial density enhancements invoked to bind the waists of bipolar nebulae.
We propose to search for new irradiated jets and protostellar outflows, shocks, protoplanetary di... more We propose to search for new irradiated jets and protostellar outflows, shocks, protoplanetary disks seen in silhouette (dark proplyds), and photo-ablating disks (bright proplyds), in the Carina Nebula with narrow-band filters and the MOSAIC camera on the CTIO 4 meter. Pilot observations obtained last December have demonstrated that this region contains a rich harvest of disks and outflows. A complete MOSAIC survey is needed to determine their population. The Carina Nebula is the most massive star forming region with the largest population of early O stars in which circumstellar disks, irradiated jets, and protostellar jets (Herbig-Haro objects) have so far been found. This is because Carina is much closer to us than other clusters with comparable populations of massive stars. These observations will extend our understanding of low-mass star formation, outflow production and impacts on the surrounding medium, and protoplanetary disk survival - to regions where the most massive stars are born. A detailed investigation of the Carina Nebula will provide a fundamental stepping stone to understanding how these processes operate in luminous H II region complexes in our Galaxy, the LMC and SMC, and in other galaxies.
We propose to probe the line emission from nearby star forming regions in the 5 to 37 micron spec... more We propose to probe the line emission from nearby star forming regions in the 5 to 37 micron spectral range using the slit-scan mode of IRS. Our goals are: [1] Measure the fluxes produced by the pure rotational lines of molecular hydrogen and other spectral features in the 5 to 38 micrometer region from the surroundings of 4 well-studied and nearby outflow sources. [2] Trace the intermediate velocity (2 to 30 km/sec) shocks in outflow regions. Such emission is predicted by models in which high velocity motions traced by optical and near-IR emission lines (Herbig-Haro objects) accelerate molecular outflows and degrade into turbulent motions. We will obtain slit-scan maps in the LL and SL modes of IRS of arc-minute scale regions surrounding HH 211, HH212, L1448c and, NGC 2071. By observing these four sources, we will compare the mid-IR emission lines produced by regions supporting various levels of star formation activity ranging from the birth of isolated single stars, to small groups, to rich clusters containing over 100 YSOs and stars as massive as 8 to 10 Solar masses.
Astronomical Journal, 2009
We have used deep optical (Hα and [S ii]) and near-IR (H 2 and K S ) images and catalogs of proto... more We have used deep optical (Hα and [S ii]) and near-IR (H 2 and K S ) images and catalogs of protostars based on optical and infrared data to follow up our previous observations and examine the protostellar outflow population in the Barnard 1 (B1) dark cloud. The deep images presented here link shocks at the low extinction periphery of the cloud to an outflow system that bisects the confused core of B1. In addition, we find that a deeply embedded infrared shock, previously identified as a protostar, is likely the impact of a flow on a submillimeter clump. In all, we detail nine outflow systems in this cloud, eight of which have clearly identified source protostars.
Astrophysical Journal Supplement Series, 2010
We present a catalog of 8358 sources extracted from images produced by the Bolocam Galactic Plane... more We present a catalog of 8358 sources extracted from images produced by the Bolocam Galactic Plane Survey (BGPS). The BGPS is a survey of the millimeter dust continuum emission from the northern Galactic plane. The catalog sources are extracted using a custom algorithm, Bolocat, which was designed specifically to identify and characterize objects in the large-area maps generated from the Bolocam instrument. The catalog products are designed to facilitate follow-up observations of these relatively unstudied objects. The catalog is 98% complete from 0.4 Jy to 60 Jy over all object sizes for which the survey is sensitive (< 3.5 ′ ). We find that the sources extracted can best be described as molecular clumps -large dense regions in molecular clouds linked to cluster formation. We find the flux density distribution of sources follows a power law with dN/dS ∝ S −2.4±0.1 and that the mean Galactic latitude for sources is significantly below the midplane: b = (−0.095 ± 0.001) • .
Astronomical Journal, 2006
We present a survey of shocks and outflows in the Chamaeleon I star-forming complex using Hα, [S ... more We present a survey of shocks and outflows in the Chamaeleon I star-forming complex using Hα, [S II], and SDSS i' images obtained from the ground, an i' image obtained with the Hubble Space Telescope, and 4.5 μm images obtained with the Infrared Array Camera (IRAC) on the Spitzer Space Telescope. We find new Herbig-Haro (HH) objects and extensions to the previously cataloged shocks that trace parts of at least 20 distinct outflows from young stars. Some HH objects mark the presence of giant outflows, the largest of which is powered by Cha-MMS1 and associated with HH 49/50 near the Ced 110 region. Other large flows are powered by Cha-MMS2 in the Ced 112 region and the IRN in the Ced 111 region. Although some shocks exhibit infrared emission in the IRAC bands, most notably HH 49/50 (the ``tornado''), most outflows in the Cha I clouds are not detected in the Spitzer IRAC bands. This result is consistent with the general lack of extensive 2.12 μm H2 emission from Cha I.
We present the Bolocam Galactic Plane Survey (BGPS), a 1.1 mm continuum survey at 33 effective re... more We present the Bolocam Galactic Plane Survey (BGPS), a 1.1 mm continuum survey at 33 effective resolution of 170 square degrees of the Galactic Plane visible from the northern hemisphere. The BGPS is one of the first large area, systematic surveys of the Galactic Plane in the millimeter continuum without arXiv:1011.0691v1 [astro-ph.GA] 2 Nov 2010 -2pre-selected targets. The survey is contiguous over the range −10.5 ≤ l ≤ 90.5, |b| ≤ 0.5. Towards the Cygnus X spiral arm, the coverage was flared to |b| ≤ 1.5 for 75.5 ≤ l ≤ 87.5. In addition, cross-cuts to |b| ≤ 1.5 were made at l = 3, 15, 30 and 31. The total area of this section is 133 square degrees. With the exception of the increase in latitude, no pre-selection criteria were applied to the coverage in this region. In addition to the contiguous region, four targeted regions in the outer Galaxy were observed: IC1396 (9 square degrees, 97.5 ≤ l ≤ 100.5, 2.25 ≤ b ≤ 5.25), a region towards the Perseus Arm (4 square degrees centered on l = 111, b = 0 near NGC7538), W3/4/5 (18 square degrees, 132.5 ≤ l ≤ 138.5) and Gem OB1 (6 square degrees, 187.5 ≤ l ≤ 193.5).
Astronomical Journal, 2004
... A NEW GIANT HERBIG-HARO FLOW IN L1451 Josh Walawender, 1,2 John Bally, 1,2 Bo Reipurth, 3 and... more ... A NEW GIANT HERBIG-HARO FLOW IN L1451 Josh Walawender, 1,2 John Bally, 1,2 Bo Reipurth, 3 and Colin Aspin 4 ... The flow is driven by the Class I protostar IRAS 03235+3004 embedded in a bright-rimmed, sharp-edged cometary cloud facing northeast. ...
Astronomical Journal, 2005
... Josh Walawender, 1, 2 John Bally, 1, 2 Helen Kirk, 3, 4 and Doug Johnstone 3, 4 ... To minimi... more ... Josh Walawender, 1, 2 John Bally, 1, 2 Helen Kirk, 3, 4 and Doug Johnstone 3, 4 ... To minimize negative &#x27;&#x27;bowling&#x27;&#x27; around bright sources, all points with values outside of Æ5 times the mean noise per pixel were set to those values before convolution. ...
Astronomical Journal, 2009
New observations of protostellar outflows associated with young stars in two of Orion's outlying ... more New observations of protostellar outflows associated with young stars in two of Orion's outlying cometary clouds, L1622 and L1634, are presented. The Hα surface brightness of the bright rims are used to argue that both clouds are located at a distance of about 400 pc in the interior of the Orion superbubble where they are illuminated by Orion's massive stars. Spitzer IRAC and MIPS images reveal 28 candidate young stellar objects (YSOs). Combined with the 14 spectroscopically confirmed T Tauri stars, there are at least 34 YSOs in L1622. Narrow-band images have led to the identification of about a dozen shock complexes in L1622. At least six belong to a highly collimated externally irradiated, bipolar jet, HH 963, that is powered by a low-luminosity Class II YSO located outside the projected edge of the L1622 dark cloud. However, the sources of most shocks remain unclear. The Spitzer/IRAC images reveal a compact, highly obscured, S-symmetric outflow brightest in the 4.5 μm images. A faint [S II] counter part, HH 962, is associated with the western end of this flow which appears to be powered by an obscured source in the L1622 cloud interior. The currently identified sample of YSOs implies a star formation efficiency of about 4% for L1622. The L1634 cloud contains nine YSOs and three outflows, including the well known HH 240/241 system. A new flow, HH 979, is powered by the embedded YSO IRS7 in L1634 and crosses the eastern lobe of the HH 240 outflow. Spitzer/IRAC images show 4.5 μm emission indicating molecular shocks from the Herbig-Haro objects closest to IRS 7. A YSO embedded in a condensation located 5' north of HH 240/241 is identified in the Spitzer images. This source drives an irradiated outflow, HH 980, whose lobes emerge into the ionized environment of the Orion-Eridanus superbubble interior. The star formation efficiency of L1634 is estimated to be about 3%.
Astronomical Journal, 2010
A population of 11 faint, collimated jets has been discovered in the northern part of the L1641 c... more A population of 11 faint, collimated jets has been discovered in the northern part of the L1641 cloud in the region of HH 1/2, HH 34, and the L1641-N cluster. These jets were missed in previous imaging surveys on account of their weak emission, and they were discovered only on deep exposures with the Subaru 8m telescope. With these new faint jets, the number of HH flows within the area surveyed has doubled. This suggests that collimated jets from young stars may be more common than assumed so far. It is noteworthy that all of the jets are associated with optically visible stars with r-magnitudes ranging from 13.8 to 22.0. The driving sources of jets in regions flooded by ultraviolet radiation from nearby OB stars are known to be excavated by photo-ionization, and in three cases remnant Hα emission envelopes are found associated with the sources, although the more benign environment in the region observed here, about 10 pc distant from the Orion Nebula Cluster, makes the optical visibility of all these sources rather surprising. Such faint jets from visible stars represent either the final vestiges of the outflow phenomenon, or they are triggered by disturbances of the remnant disks, possibly initiated by the orbital evolution of binaries that spiral in to form close binaries. Among the known Hα emission stars within the region surveyed, 8% are found to be associated with jets.
Astronomical Journal, 2006
The Circinus giant molecular cloud is a little explored region that deserves closer study owing t... more The Circinus giant molecular cloud is a little explored region that deserves closer study owing to the many signs of vigorous low-mass star formation in the form of Hα emission stars, Herbig-Haro objects, molecular outflows, and embedded sources. The western part of the cloud complex has a filamentary structure with numerous cavities, indicating the effect of powerful molecular outflows. It is likely that the current strong star formation activity was triggered by a supernova explosion. Our present limited knowledge about this region is summarized, and several particularly interesting sources are discussed.
Astrophysical Journal Supplement Series, 2011
We present the Bolocam Galactic Plane Survey (BGPS), a 1.1 mm continuum survey at 33'' effective ... more We present the Bolocam Galactic Plane Survey (BGPS), a 1.1 mm continuum survey at 33'' effective resolution of 170 deg2 of the Galactic Plane visible from the northern hemisphere. The BGPS is one of the first large area, systematic surveys of the Galactic Plane in the millimeter continuum without pre-selected targets. The survey is contiguous over the range -10.5 <= l <= 90.5, |b| <= 0.5. Toward the Cygnus X spiral arm, the coverage was flared to |b| <= 1.5 for 75.5 <= l <= 87.5. In addition, cross-cuts to |b| <= 1.5 were made at l= 3, 15, 30, and 31. The total area of this section is 133 deg2. With the exception of the increase in latitude, no pre-selection criteria were applied to the coverage in this region. In addition to the contiguous region, four targeted regions in the outer Galaxy were observed: IC1396 (9 deg2, 97.5 <= l <= 100.5, 2.25 <= b <= 5.25), a region toward the Perseus Arm (4 deg2 centered on l = 111, b = 0 near NGC 7538), W3/4/5 (18 deg2, 132.5 <= l <= 138.5), and Gem OB1 (6 deg2, 187.5 <= l <= 193.5). The survey has detected approximately 8400 clumps over the entire area to a limiting non-uniform 1σ noise level in the range 11-53 mJy beam-1 in the inner Galaxy. The BGPS source catalog is presented in a previously published companion paper. This paper details the survey observations and data reduction methods for the images. We discuss in detail the determination of astrometric and flux density calibration uncertainties and compare our results to the literature. Data processing algorithms that separate astronomical signals from time-variable atmospheric fluctuations in the data timestream are presented. These algorithms reproduce the structure of the astronomical sky over a limited range of angular scales and produce artifacts in the vicinity of bright sources. Based on simulations, we find that extended emission on scales larger than about 5farcm9 is nearly completely attenuated (>90%) and the linear scale at which the attenuation reaches 50% is 3farcm8. Comparison with other millimeter-wave data sets implies a possible systematic offset in flux calibration, for which no cause has been discovered. This presentation serves as a companion and guide to the public data release (http://irsa.ipac.caltech.edu/Missions/bolocam.html) through NASA's Infrared Processing and Analysis Center (IPAC) Infrared Science Archive (IRSA). New data releases will be provided through IPAC-IRSA with any future improvements in the reduction. The BGPS provides a complementary long-wavelength spectral band for the ongoing ATLASGAL and Herschel-SPIRE surveys, and an important database and context for imminent observations with SCUBA-2 and ALMA.
Astrophysical Journal, 2010
We present the 1.1 millimeter Bolocam Galactic Plane Survey (BGPS) observations of the Gemini OB1... more We present the 1.1 millimeter Bolocam Galactic Plane Survey (BGPS) observations of the Gemini OB1 molecular cloud complex, and targeted NH 3 observations of the BGPS sources. When paired with molecular spectroscopy of a dense gas tracer, millimeter observations yield physical properties such as masses, radii, mean densities, kinetic temperatures and line widths. We detect 34 distinct BGPS sources above 5σ = 0.37 Jy beam −1 with corresponding 5σ detections in the NH 3 (1,1) transition. Eight of the objects show water maser emission (20%). We find a mean millimeter source FWHM of 1.12 pc, and a mean gas kinetic temperature of 20 K for the sample of 34 BGPS sources with detections in the NH 3 (1,1) line. The observed NH 3 line widths are dominated by non-thermal motions, typically found to be a few times the thermal sound speed expected for the derived kinetic temperature. We calculate the mass for each source from the millimeter flux assuming the sources are isothermal and find a mean isothermal mass within a 120 ′′ aperture of 230 ± 180 M ⊙ . We find a total mass of 8,400 M ⊙ for all BGPS sources in the Gemini OB1 molecular cloud, representing 6.5% of the cloud mass. By comparing the millimeter isothermal mass to the virial mass within a radius equal to the mm source size calculated from the NH 3 line widths, we find a mean virial parameter (M vir /M iso ) of 1.0±0.9 for the sample. We find mean values for the distributions of column densities of 1.0 × 10 22 cm −2 for H 2 , and 3.0 × 10 14 cm −2 for NH 3 , giving a mean NH 3 abundance of 3.0 × 10 −8 relative to H 2 . We find volume-averaged densities on the order of 10 3 − 10 4 cm −3 . The sizes and densities suggest that in the Gem OB 1 region the BGPS is detecting the clumps from which stellar clusters form, rather than smaller, higher density cores where single stars or small multiple systems form.