We present a spatially resolved 894 micron map of the circumstellar disk of the Butterfly star in Taurus (IRAS 04302+2247), obtained with the Submillimeter Array (SMA). The predicted and observed radial brightness profile agree well in the outer disk region, but differ in the inner region with an outer radius of ~80-120 AU. In particular, we find a local minimum of the radial brightness distribution at the center, which can be explained by an increasing density / optical depth combined with the decreasing vertical extent of the disk towards the center. Our finding indicates that young circumstellar disks can be optically thick at wavelengths as long as 894 micron. While earlier modeling lead to general conclusions about the global disk structure and, most importantly, evidence for grain growth in the disk (Wolf, Padgett, & Stapelfeldt 2003), the presented SMA observations provide more detailed constraints for the disk structure and dust grain properties in the inner, potentially planet-forming region (inside ~80-120 AU) vs. the outer disk region (~120-300 AU).
We present a model of the circumstellar environment of the so-called ``Butterfly Star'' in Taurus (IRAS 04302+2247). The appearance of this young stellar object is dominated by a large circumstellar disk seen edge-on and the light scattering lobes above the disk. The model is based on multi-wavelength continuum observations: Millimeter maps and high-resolution near-infrared images obtained with HST/NICMOS. It was found that the disk and envelope parameters are comparable with those of the circumstellar environment of other young stellar objects. A main result is that the dust properties must b…
We present 800 micron continuum photometry of pre-main-sequence binary stars with projected separations a_p < 150 AU in the Sco-Oph star-forming region. Combining our observations with published 1300 micron photometry, we find that binaries in Sco-Oph with 1 < a_p < 50--100 AU have lower submillimeter fluxes than wider binaries or single stars, as previously found for Taurus- Auriga binaries. The wide binaries and single stars have indistinguishable submillimeter flux distributions. Thus, binary companions with separations less than 50--100 AU significantly influence the nature of associated d…
We present a sensitive, multiwavelength submillimeter continuum survey of 153 young stellar objects in the Taurus-Auriga star formation region. The submillimeter detection rate is 61% to a completeness limit of ~10 mJy (3-sigma) at 850 microns. The inferred circumstellar disk masses are log-normally distributed with a mean mass of ~0.005 solar masses and a large dispersion (0.5 dex). Roughly one third of the submillimeter sources have disk masses larger than the minimal nebula from which the solar system formed. The median disk to star mass ratio is 0.5%. The empirical behavior of the submilli…
We present new multiwavelength submillimeter continuum measurements of the circumstellar dust around 48 young stars in the $ρ$ Ophiuchus dark clouds. Supplemented with previous 1.3 mm observations of an additional 99 objects from the literature, the statistical distributions of disk masses and submillimeter colors are calculated and compared to those in the Taurus-Auriga region. These basic submillimeter properties of young stellar objects in both environments are shown to be essentially identical. As with their Taurus counterparts, the $ρ$ Oph circumstellar dust properties are shown to evolve…
Whole disk brightness ratios for Jupiter, Saturn, and Mars are reported at 5.7, 9.5, 16.4, and 22.5 cm$^{-1}$. Using models for the brightness temperature of Mars, the whole disk brightness temperatures for Jupiter and Saturn are also given for the four frequencies.
We present a high spatial resolution submillimeter continuum survey of 24 circumstellar disks in the Tau-Aur and Oph-Sco star formation regions using the SMA. In the context of a simple model, we use broadband SEDs and submillimeter visibilities to derive constraints on some basic parameters that describe the structure of these disks. For the typical disk in the sample we infer a radial surface density distribution Σ~ r^-p with a median p ~ 0.5, although consideration of the systematic effects of some of our assumptions suggest that steeper distributions with p ~ 0.7-1.0 are more reasonable. T…
We highlight two recent studies of circumstellar disks in the Taurus and Orion star forming regions. Using the JCMT and CSO, we measure disk fluxes in Taurus over a wide range of submillimeter wavelengths and determine the frequency dependence of the dust opacity. We find clear evidence for a systematic change in its behavior with time, most readily explained by grain growth. Using the SMA, we observed the protoplanetary disks (proplyds) in the Orion Trapezium cluster. The combination of high resolution, high frequency, and high sensitivity that this instrument provides made it possible to res…
We present high-resolution aperture synthesis images from the Submillimeter Array of the 225 GHz (1.3 mm) continuum and CO J=2-1 line emission from the disks around components of the hierarchical triple system SR 24, located in the Ophiuchus star-forming region. The most widely separated component, SR 24 S (with a projected semimajor axis of 832 AU), has a circumstellar disk with properties typical of those around single T Tauri stars. The binary SR 24 N (with a projected semimajor axis of 32 AU) is undetected in the continuum, but has strong, resolved CO emission which likely originates in a …
Solid particles with the composition of interstellar dust and power-law size distribution dn/da propto a^{-p} for a < a_max with a_{max} > 3 lambda and 3 < p < 4 will have submm opacity spectral index beta(lambda) = dln(kappa)/dln(nu) approx (p-3) beta_{ism}, where beta_{ism} approx 1.7 is the opacity spectral index of interstellar dust material in the Rayleigh limit. For the power-law index p approx 3.5 that characterizes interstellar dust, and that appears likely for particles growing by agglomeration in protoplanetary disks, grain growth to sizes a > 3 mm will result in beta(1 mm) < ~1. Gra…
A 850 micron map of the interacting spiral galaxy M51 shows well-defined spiral arms, closely resembling the structures seen in CO and HI emission. However, most of the 850 micron emission originates in an underlying exponential disk, a component that has not been observed before in a face-on galaxy at these wavelengths. The scale-length of this disk is 5.45 kpc, which is somewhat larger than the scale-length of the stellar disk, but somewhat smaller than that of atomic hydrogen. Its profile can not be explained solely by a radial disk temperature gradient but requires the underlying dust to h…
We present ~2"-4" aperture synthesis observations of the circumstellar disk surrounding the nearby young star TW Hya in the CO J=2--1 and J=3--2 lines and associated dust continuum obtained with the partially completed Submillimeter Array. The extent and peak flux of the 230 and 345 GHz dust emission follow closely the predictions of the irradiated accretion disk model of Calvet et al. (2002). The resolved molecular line emission extends to a radius of at least 200 AU, the full extent of the disk visible in scattered light, and shows a clear pattern of Keplerian rotation. Comparison of the ima…
The nature of far-infrared dust emission toward main sequence stars, whether interstellar or circumstellar, can be deduced from submillimeter photometry. We present JCMT/SCUBA flux measurements at 850 microns toward 8 stars with large photospheric excesses at 60-100 microns. 5 sources were detected at 3-sigma or greater significance and one was marginally detected at 2.5-sigma. The inferred dust masses and temperatures range from 0.033 to 0.24 Earth masses and 43-65 K respectively. The frequency behavior of the opacity, tau_nu ~ nu^beta, is relatively shallow, beta < 1. These dust properties a…
Deep submillimeter (submm) continuum imaging observations of the starburst galaxy M82 are presented at 350, 450, 750 and 850 micron wavelengths, that were undertaken with the Submillimetre Common-User Bolometer Array (SCUBA) on the James Clerk Maxwell Telescope in Hawaii. The presented maps include a co-addition of submm data mined from the SCUBA Data Archive. The co-added data produce the deepest submm continuum maps yet of M82, in which low-level 850 micron continuum has been detected out to 1.5kpc, at least 10% farther in radius than any previously published submm detections of this galaxy.…
Observations of submillimeter lines of CO (up to J=6-5), HCO+, HCN (up to J=4-3) and their isotopes from circumstellar disks around low mass pre-main sequence stars are presented. The different line ratios and optical depths indicate that most of the observed line emission arises from an intermediate disk layer with high densities of 1E6-1E8 cm-3 and moderately warm temperatures in the outer regions. The data are compared with three disk models from the literature using a full 2D Monte Carlo radiative transfer code. The abundances of the molecules are constrained from the more optically thin 1…
We have made sensitive 800-micron continuum observations of low-mass, pre-main sequence (PMS) binary stars with projected separations less than 25 AU in Taurus-Auriga to study disks in the young binary environment. We did not detect any of the observed binaries, with typical 3-sigma upper limits of about 30 mJy. Combining our observations with previous 1300-micron observations of PMS Taurus binaries by Beckwith et al. (1990) and others, we find that the submillimeter fluxes from binaries with projected separations between 1 AU and 50 AU are significantly lower than fluxes from binaries with pr…
Circumstellar disks are expected to form early in the process that leads to the formation of a young star, during the collapse of the dense molecular cloud core. It is currently not well understood at what stage of the collapse the disk is formed or how it subsequently evolves. We aim to identify whether an embedded Keplerian protoplanetary disk resides in the L1489 IRS system. Given the amount of envelope material still present, such a disk would respresent a very young example of a protoplanetary disk. Using the Submillimeter Array (SMA) we have observed the HCO$^+$ $J=$ 3--2 line with a res…
The Submillimeter Array has opened a new window to study the innermost warm and dense regions of the envelopes and disks around deeply embedded protostars. This paper presents high-angular resolution (< 2'') submillimeter observations of the class 0 young stellar object NGC1333-IRAS2A. Dust continuum emission and lines of complex organic molecules such as CH3OCH3 and CH3OCHO, high excitation CH3OH transitions, deuterated methanol CH3OD as well as lines of CO, HCN, H13CN, SO and SO2 are detected on < 200 AU scales. The observations are interpreted using detailed radiative transfer models of the…
Mid-infrared spectrophotometric observations have revealed a small sub-class of circumstellar disks with spectral energy distributions (SEDs) suggestive of large inner gaps with low dust content. However, such data provide only an indirect and model dependent method of finding central holes. We present here the direct characterization of a 40 AU radius inner gap in the disk around LkHa 330 through 340 GHz (880 micron) dust continuum imaging with the Submillimeter Array (SMA). This large gap is fully resolved by the SMA observations and mostly empty of dust with less than 1.3 x 10^-6 M_solar of…
Images covering the central 450 by 100 arcsecond (about 8.0 by 2.0 kpc) of NGC 5128 (Centaurus A) obtained using SCUBA at 850 and 450 micron with beam sizes of 14.5 and 8 arcsecond respectively, are presented. These data are compared with those obtained at other wavelengths, in particular the optical, mid-infrared, and far-infrared continuum. The sensitive 850 and 450 micron images show that the submillimeter (submm) continuum morphology and spectral index distribution of Centaurus A comprise four regions: an unresolved AGN core, an inner jet interacting with gas in the dust lane, an inner dis…
This paper presents a large spectral line and continuum survey of 8 deeply embedded, low-mass protostellar cores using the Submillimeter Array. Each source was observed in high excitation lines of some of the most common molecular species, CO, HCO+, CS, SO, H2CO, CH3OH and SiO. Line emission from 11 species originating from warm and dense gas have been imaged at high angular resolution (1-3"; typically 200-600 AU) together with continuum emission at 230 GHz (1.3 mm) and 345 GHz (0.8 mm). Compact continuum emission is observed for all sources which likely originates in marginally optically thic…
High dynamic range imaging of submillimeter dust emission from the envelopes of eight young protostars in the Taurus and Perseus star-forming regions has been carried out using the SCUBA submillimeter camera on the James Clerk Maxwell Telescope. Good correspondence between the spectral classifications of the protostars and the spatial distributions of their dust emission is observed, in the sense that those with cooler spectral energy distributions also have a larger fraction of the submillimeter flux originating in an extended envelope compared with a disk. This results from the cool sources …
We consider current state of star formation theory and requirements to observations in millimeter and submillimeter ranges which are necessary for resolution of the most actual problems of the physics of star formation. Two key features of star-forming regions which define observational requirements to their studies, are relatively low energy of processes that take place there and smallness of corresponding spatial scales. This is especially true for the objects in the latest stages of ``pre-stellar'' evolution, that is, hot cores, hyper- and ultracompact HII regions, and protoplanetary disks.…
Using the Submillimeter Array (SMA) we have imaged for the first time the 321.226 GHz, 10_{29}-9_{36} ortho-H2O maser emission. This is also the first detection of this line in the Cepheus A high-mass star-forming region. The 22.235 GHz, 6_{16}-5_{23} water masers were also observed with the Very Large Array 43 days following the SMA observations. Three of the nine detected submillimeter maser spots are associated with the centimeter masers spatially as well as kinematically, while there are 36 22 GHz maser spots without corresponding submillimeter masers. In the HW2 source, both the 321 GHz a…
We report the results of H13CO+(1-0), CO(1-0), and 3.3 mm dust continuum observations toward one of the strongest mm-wave sources in OMC-3, MMS 7, with the Nobeyama Millimeter Array (NMA) and the Nobeyama 45 m telescope. With the NMA, we detected centrally-condensed 3.3 mm dust-continuum emission which coincides with the MIR source and the free-free jet. Our combined H13CO+ observations have revealed a disk-like envelope. The size and the mass of the disk-like envelope are 0.15 times 0.11 pc and 5.1 - 9.1 M_sun, respectively. The combined map also shows that the outer portion of the disk-like …
We present high spatial resolution (< 0.3" = 40$ AU) Submillimeter Array observations of the 865 micron continuum emission from the circumstellar disk around the young star DoAr 25. Despite its bright millimeter emission, this source exhibits only a comparatively small infrared excess and low accretion rate, suggesting that the material and structural properties of the inner disk may be in an advanced state of evolution. A simple model of the physical conditions in the disk is derived from the submillimeter visibilities and the complete spectral energy distribution using a Monte Carlo radiativ…
Improving our understanding of the initial conditions and earliest stages of protostellar collapse is crucial to gain insight into the origin of stellar masses, multiple systems, and protoplanetary disks. Observationally, there are two complementary approaches to this problem: (1) studying the structure and kinematics of prestellar cores observed prior to protostar formation, and (2) studying the structure of young (e.g. Class 0) accreting protostars observed soon after point mass formation. We discuss recent advances made in this area thanks to (sub)millimeter mapping observations with large …
We present the results of an 850 micron JCMT/SCUBA survey for dust around 13 nearby solar mass stars. The dust mass sensitivity ranged from 0.005 to 0.16 Earth masses. Three sources were detected in the survey, one of which (HD 107146) has been previously reported. One of the other two submillimeter sources, HD 104860, was not detected by IRAS and is surrounded by a cold, massive dust disk with a dust temperature and mass of Tdust = 33 K and Mdust = 0.16 Mearth. The third source, HD 8907, was detected by IRAS and ISO at 60-87 microns, and has a dust temperature and mass Tdust = 48 K and Mdust …
We investigate the possibility to detect giant planets that are still embedded in young circumstellar disks. Based on models with different stellar, planetary, and disk masses, and different radial positions of the planet we analyze the resulting submillimeter appearance of these systems. We find that the influence of the planet on the spectral energy distribution could not be distinguished from that of other disk parameters. However, dust reemission images of the disks show that the hot region in the proximity of a young planet, along with the gap, could indeed be detected and mapped with the…
We present results of a study aimed at deriving fundamental properties of circumstellar debris disks from observed infrared to submillimeter spectral energy distributions. This investigation is motivated by increasing telescope/detector sensitivity, in particular the expected availability of the Space Infrared Telescope Facility (SIRTF) followed by the Stratospheric Observatory for Infrared Astronomy (SOFIA), which will enable detailed studies with large source samples of late stage circumstellar disk and planetary system evolution. We base our study on an analytic model of the disk density di…
Submillimeter and near-infrared images of cool dusty debris disks and rings suggest the existence of unseen planets. At dusty but non-imaged stars, semi-major axes of associated planets can be estimated from the dust temperature. For some young stars these semi-major axes are greater than an arc second as seen from Earth. Such stars are excellent targets for sensitive near-infrared imaging searches for warm planets. To probe the full extent of the dust and hence of potential planetary orbits, SIRTF observations should include measurements with the 160mu filter.
We investigate the possibility to find evidence for planets in circumstellar disks by infrared and submillimeter interferometry. We present simulations of a circumstellar disk around a solar-type star with an embedded planet of 1 Jupiter mass. The three-dimensional (3D) density structure of the disk results from hydrodynamical simulations. On the basis of 3D radiative transfer simulations, images of this system were calculated. The intensity maps provide the basis for the simulation of the interferometers VLTI (equipped with the mid-infrared instrument MIDI) and ALMA. While MIDI/VLTI will not …
We investigate the possibility to find evidence for planets in circumstellar disks by infrared and submillimeter interferometry. Hydrodynamical simulations of a circumstellar disk around a solar-type star with an embedded planet of 1 Jupiter mass are presented. On the basis of 3D radiative transfer simulations, images of this system are calculated. These intensity maps provide the basis for the simulation of the interferometers VLTI (equipped with the mid-infrared instrument MIDI) and ALMA. While ALMA will provide the necessary basis for a direct gap and therefore indirect planet detection, MI…
We present Submillimeter Array observations of the Herbig Ae star HD169142 in 1.3 millimeter continuum emission and 12CO J=2-1 line emission at 1.5 arcsecond resolution that reveal a circumstellar disk. The continuum emission is centered on the star position and resolved, and provides a mass estimate of about 0.02 solar masses for the disk. The CO images show patterns in position and velocity that are well matched by a disk in Keplerian rotation with low inclination to the line-of-sight. We use radiative transfer calculations based on a flared, passive disk model to constrain the disk paramete…
The nature of the energy source powering anomalous X-ray pulsars is uncertain. Proposed scenarios involve either an ultramagnetized neutron star, or accretion onto a neutron star. We consider the accretion model proposed recently by Chatterjee, Hernquist & Narayan, in which a disk is fed by fallback material following a supernova. We compute the optical, infrared, and submillimeter emission expected from such a disk, including both viscous dissipation and reradiation of X-ray flux impinging on the disk from the pulsar. We find that it is possible with current instruments to put serious constra…
We have imaged the circumstellar envelope around the binary protostar L1551 IRS 5 in CS (J=7-6) and 343 GHz continuum emission at ~ 3 arcsec resolution using the Submillimeter Array. The continuum emission shows an elongated structure (~ 220 x 100 AU) around the binary perpendicular to the axis of the associated radio jet. The CS emission extends over ~ 400 AU, appears approximately circularly symmetric, and shows a velocity gradient from southeast (blueshifted) to northwest (redshifted). The direction of the velocity gradient is different from that observed in C18O (J=1-0). This may be becaus…
We model the spectral energy distribution (SED) from the mid-infrared to submillimeter of the ring-like disk of HR 4796A, the dustiest A-type star. We consider dust made either of coagulated but otherwise unaltered protostellar interstellar grains, or grains that are highly-processed in a protostellar/protoplanetary nebula with silicate dust annealed and carbon dust oxidized. Both types of dust are successful in reproducing the observed SED, provided that the grains are highly fluffy, with a vacuum volume fraction of \~90%. We find no evidence for the existence of a hot ``zodiacal dust'' compo…
We have monitored the millimeter and submillimeter emission from the young stellar object GG Tau, a T Tauri binary system surrounded by a massive circumbinary disk. We find that between 1992 and 1994, the flux has increased significantly at 800, 1100, and 1300 microns, resulting in a steepening of the observed spectral energy distribution at those wavelengths. Such an increase appears consistent with a modest increase in disk luminosity (a factor of two). The increase in the effective disk temperature might arise from a slight change in the disk heating processes. Alternatively, the flux incre…
We model the infrared (IR) emission from the ring-like dust disk around the main-sequence (MS) star Epsilon Eridani, a young analog to our solar system, in terms of a porous dust model previously developed for the extended wedge-shaped disk around the MS star $β$ Pictoris and the sharply truncated ring-like disks around the Herbig Ae/Be stars HR 4796A and HD 141569A. It is shown that the porous dust model with a porosity of $\simali$90% is also successful in reproducing the IR to submillimeter dust emission spectral energy distribution as well as the 850$\mum$ flux radial profile of the dust r…
The results from a single-dish molecular line survey of a set of 18 deeply embedded young stellar objects are summarized. More than 40 lines from 16 different species were observed with the JCMT, Onsala, IRAM 30m and SEST telescopes. The multi-transition data are analyzed using a temperature and density structure derived from models of the dust continuum emission. For the outer envelope (>300 AU), the data indicate a `drop' abundance profile for many species, with normal abundances in the outer- and innermost regions and highly depleted abundances in an intermediate zone. This zone is bounded …
We present a census of the population of deeply embedded young stellar objects (YSOs) in the Ophiuchus molecular cloud complex based on a combination of Spitzer Space Telescope mid-infrared data from the "Cores to Disks" (c2d) legacy team and JCMT/SCUBA submillimeter maps from the COMPLETE team. We have applied a method developed for identifying embedded protostars in Perseus to these datasets and in this way construct a relatively unbiased sample of 27 candidate embedded protostars with envelopes more massive than our sensitivity limit (about 0.1 M_sun). Embedded YSOs are found in 35% of the …
This paper examines the density and velocity structure of envelopes around young stellar objects through submillimeter continuum imaging of four objects in Taurus and previously obtained molecular-line data. Observations carried out with the SCUBA on the JCMT at 850 and 450 micron of L1489 IRS, L1535 IRS, L1527 IRS, and TMC 1 reveal ~2000 AU elongated structures embedded in extended envelopes. The density distribution in these envelopes is equally well fit by a radial power-law of index p=1.0-2.0 or with a collapse model such as that of Shu (1997: ApJ, 214, 488). This inside-out collapse model…
Photodissociation Region (PDR) models are computed over a wide range of physical conditions, from those appropriate to giant molecular clouds illuminated by the interstellar radiation field to the conditions experienced by circumstellar disks very close to hot massive stars. These models use the most up-to-date values of atomic and molecular data, the most current chemical rate coefficients, and the newest grain photoelectric heating rates which include treatments of small grains and large molecules. In addition, we examine the effects of metallicity and cloud extinction on the predicted line …
We report a new and complete model of the beta Pictoris disk, which succeeds in accounting for both the surface brightness distribution, warp characteristics, the outer ``butterfly'' asymmetry as observed by HST/STIS in scattered light, as well as the infrared emission. Our model includes the presence of a disk of planetesimals extending out to 120-150 AU, perturbed gravitationally by a giant planet on an inclined orbit, following the approach of Mouillet et al. (1997b). At any time, the planetesimal disk is assumed to be the source of a distribution of grains produced through collisional evol…
We report a dual-band observation at 223 and 654 GHz (460 micron) toward an ultracompact (UC) HII region, G240.31+0.07, with the Submillimeter Array. With a beam size of 1"5 X 0"8, the dust continuum emission is resolved into two clumps, with clump A coincident well with an H2O maser and the UC HII region. The newly discovered clump, B, about 1"3 (~8.3 X 10^3 AU) to the southwest of clump A, is also associated with H2O masers and may be a more recent star-forming site. The continuum flux densities imply an opacity spectral index of β= 1.5 +- 0.3, suggestive of a value lower than the canonical …
This paper investigates small-scale structures of dense gas and dust around the low-mass protostellar binary NGC1333-IRAS2 using millimeter-wavelength aperture-synthesis observations from the OVRO and BIMA interferometers. The detected 3 mm continuum emission is consistent with models of the envelope around IRAS2A, based on previously reported submillimeter continuum images, down to the 3", or 500 AU, resolution of the interferometer data. Our data constrain the contribution of an unresolved point source to 22 mJy. Within the accuracy of the parameters describing the envelope model, the point …
We present results from the observations and modeling of seventeen Class I cores with the Submillimetre Common Users Bolometer Array (SCUBA) on the James Clerk Maxwell Telescope (JCMT). By modeling the transfer of radiation through the envelope for nine cores, we find, for a power law distribution n(r)=n_f(r/r_f)^-p, the average and standard deviation p=1.6 +/- 0.4 and a median of p=1.8. However, the inclusion of a disk or other point-like component can cause the derived p to be shallower by as much as 0.5. In addition, we test the Shu collapse model for our sources and discuss the application…
