- ID:
- ivo://CDS.VizieR/J/A+A/619/A161
- Title:
- ALMA images of HD 135344B
- Short Name:
- J/A+A/619/A161
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Spiral arms, rings and large scale asymmetries are structures observed in high resolution observations of protoplanetary disks, and it appears that some of the disks showing spiral arms in scattered light also show asymmetries in millimeter-sized dust. HD 135344B is one of these disks. Planets are invoked as the origin of these structures, but no planet has been observed so far and up per limits are becoming more stringent with time. We want to investigate the nature of the asymmetric structure in the HD 135344B disk in order to understand the origin of the spirals and of the asymmetry seen in this disk. Ultimately, we aim at understanding whether or not one or more planets are needed to explain such structures. We present new ALMA sub-0.1" resolution observations at optically thin wavelengths (lambda=2.8mm and 1.9mm) of the HD 135344B disk. The high spatial resolution allows us to unambiguously characterize the mm-dust morphology of the disk. The low optical depth of continuum emission probes the bulk of the dust content of the vortex. Moreover, we combine the new observations with archival data at shorter wavelengths to perform a multi-wavelength analysis and to obtain information about the dust distribution and properties inside the observed asymmetry. We resolve the asymmetric disk into a symmetric ring + asymmetric crescent, and observe that: (1) the spectral index strongly decreases at the center of the vortex, consistent with the presence of large grains; (2) for the first time, an azimuthal shift of the peak of the vortex with wavelength is observed; (3) the azimuthal width of the vortex decreases at longer wavelengths, as expected for dust traps. These features allow to confirm the nature of the asymmetry as a vortex. Finally, under the assumption of optically thin emission, a lower limit to the total mass of the vortex is 0.3M_Jupiter_. Considering the uncertainties involved in this estimate, it is possible that the actual mass of the vortex is higher and possibly within the required values (~4M_Jupiter_) to launch spiral arms similar to those observed in scattered light. If this is the case, no outer planet is needed to explain the morphology.
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Search Results
- ID:
- ivo://CDS.VizieR/J/A+A/627/L6
- Title:
- ALMA Long Baseline maps of G17.64+0.16
- Short Name:
- J/A+A/627/L6
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the highest angular resolution (20x15mas - 44x33au) Atacama Large Millimeter/sub-millimeter Array (ALMA) observations currently possible of the proto-O-star G17.64+0.16 in Band 6. The Cycle 5 observations with baselines out to 16 km probes scales <50au and reveal the rotating disc around G17.64+0.16, a massive forming O-type star. The disc has a ring-like enhancement in the dust emission, especially visible as arc structures to the north and south. The Keplerian kinematics are most prominently seen in the vibrationally excited water line, H_2_O (Eu=3461.9K). The mass of the central source found by modelling the Keplerian rotation is consistent with 45+/-10M_{sun}_. The H30alpha (231.9GHz) radio-recombination line and the SiO (5-4) molecular line were detected at up to the 10-sigma level. The estimated disc mass is 0.6-2.6M_{sun}_ under the optically thin assumption. Analysis of the Toomre Q parameter, in the optically thin regime, indicates that the disc stability is highly dependent on temperature. The disc currently appears stable for temperatures >150K, this does not preclude that the substructures formed earlier through disc fragmentation.
- ID:
- ivo://CDS.VizieR/J/A+A/620/A31
- Title:
- ALMA maps of G17.64+0.16
- Short Name:
- J/A+A/620/A31
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present high angular resolution (~0.2") continuum and molecular emission line Atacama Large Millimeter/sub-millimeter Array (ALMA) observations of G17.64+0.16 in Band 6 (220-230GHz) taken as part of a campaign in search of circumstellar discs around (proto)-O-stars. At a resolution of ~400au the main continuum core is essentially unresolved and isolated from other strong and compact emission peaks. We detect SiO (5-4) emission that is marginally resolved and elongated in a direction perpendicular to the large-scale outflow seen in the ^13^CO (2-1) line using the main ALMA array in conjunction with the Atacama Compact Array (ACA). Morphologically, the SiO appears to represent a disc-like structure. Using parametric models we show that the position-velocity profile of the SiO is consistent with the Keplerian rotation of a disc around an object between 10-30M_{sun}_ in mass, only if there is also radial expansion from a separate structure. The radial motion component can be interpreted as a disc wind from the disc surface. Models with a central stellar object mass between 20 and 30M_{sun}_ are the most consistent with the stellar luminosity 1x10^5^L_{sun}_) and indicative of an O-type star. The H30{alpha} millimetre recombination line (231.9GHz) is also detected, but spatially unresolved, and is indicative of a very compact, hot, ionised region co-spatial with the dust continuum core. The broad line-width of the H30{alpha} emission (Full-Width-Half-Maximum=81.9km/s is not dominated by pressure-broadening but is consistent with underlying bulk motions. These velocities match those required for shocks to release silicon from dust grains into the gas phase. CH_3_CN and CH_3_OH thermal emission also shows two arc shaped plumes that curve away from the disc plane. Their coincidence with OH maser emission suggests that they could trace the inner working surfaces of a wide-angle wind driven by G17.64 which impacts the diffuse remnant natal cloud before being redirected into the large-scale outflow direction. Accounting for all observables, we suggest that G17.64 is consistent with a O-type young stellar object in the final stages of protostellar assembly, driving a wind, but that has not yet developed into a compact HII region. The existence and detection of the disc in G17.64 is likely related to its isolated and possibly more evolved nature, traits which may underpin discs in similar sources.
- ID:
- ivo://CDS.VizieR/J/ApJS/256/30
- Title:
- ALMA 1.33mm images of 10 FU Orionis-type stars
- Short Name:
- J/ApJS/256/30
- Date:
- 03 Mar 2022
- Publisher:
- CDS
- Description:
- The FU Orionis-type objects (FUors) are low-mass pre-main-sequence stars undergoing a temporary but significant increase of mass accretion rate from the circumstellar disk onto the protostar. It is not yet clear what triggers the accretion bursts and whether the disks of FUors are in any way different from the disks of nonbursting young stellar objects. Motivated by this, we conducted a 1.3mm continuum survey of 10 FUors and FUor-like objects with ALMA, using both the 7m array and the 12m array in two different configurations to recover emission at the widest possible range of spatial scales. We detected all targeted sources and several nearby objects as well. To constrain the disk structure, we fit the data with models of increasing complexity from 2D Gaussian to radiative transfer, enabling comparison with other samples modeled in a similar way. The radiative transfer modeling gives disk masses that are significantly larger than what is obtained from the measured millimeter fluxes assuming optically thin emission, suggesting that the FUor disks are optically thick at this wavelength. In comparison with samples of regular class II and class I objects, the disks of FUors are typically a factor of 2.9-4.4 more massive and a factor of 1.5-4.7 smaller in size. A significant fraction of them (65%-70%) may be gravitationally unstable.
- ID:
- ivo://CDS.VizieR/J/ApJ/831/125
- Title:
- ALMA 887{mu}m obs. of ChaI star-forming region
- Short Name:
- J/ApJ/831/125
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The disk mass is among the most important input parameter for every planet formation model to determine the number and masses of the planets that can form. We present an ALMA 887{mu}m survey of the disk population around objects from ~2 to 0.03M_{sun}_ in the nearby ~2Myr old Chamaeleon I star-forming region. We detect thermal dust emission from 66 out of 93 disks, spatially resolve 34 of them, and identify two disks with large dust cavities of about 45 au in radius. Assuming isothermal and optically thin emission, we convert the 887{mu}m flux densities into dust disk masses, hereafter M_dust_. We find that the M_dust_-M_*_ relation is steeper than linear and of the form M_dust_{propto}(M_*_)^1.3-1.9^, where the range in the power-law index reflects two extremes of the possible relation between the average dust temperature and stellar luminosity. By reanalyzing all millimeter data available for nearby regions in a self-consistent way, we show that the 1-3 Myr old regions of Taurus, Lupus, and Chamaeleon I share the same M_dust_-M_*_ relation, while the 10 Myr old Upper Sco association has a steeper relation. Theoretical models of grain growth, drift, and fragmentation reproduce this trend and suggest that disks are in the fragmentation-limited regime. In this regime millimeter grains will be located closer in around lower-mass stars, a prediction that can be tested with deeper and higher spatial resolution ALMA observations.
- ID:
- ivo://CDS.VizieR/J/ApJ/813/45
- Title:
- ALMA observations in z~0.5-3 quasars
- Short Name:
- J/ApJ/813/45
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present Atacama Large Millimeter/submillimeter Array (ALMA) 870 {mu}m (345 GHz) data for 49 high-redshift (0.47<z<2.85), luminous (11.7<log(L_bol_/L_{sun}_)<14.2) radio-powerful active galactic nuclei (AGNs), obtained to constrain cool dust emission from starbursts concurrent with highly obscured radiative-mode black hole (BH) accretion in massive galaxies that possess a small radio jet. The sample was selected from the Wide-field Infrared Survey Explorer with extremely steep (red) mid-infrared colors and with compact radio emission from NVSS/FIRST. Twenty-six sources are detected at 870 {mu}m, and we find that the sample has large mid- to far-infrared luminosity ratios, consistent with a dominant and highly obscured quasar. The rest-frame 3 GHz radio powers are 24.7<log(P_3.0GHz_/W/Hz)<27.3 and all sources are radio-intermediate or radio-loud. BH mass estimates are 7.7<log(M_BH_/M_{sun}_)<10.2. The rest-frame 1-5 {mu}m spectral energy distributions are very similar to the "Hot DOGs" (hot dust-obscured galaxies), and steeper (redder) than almost any other known extragalactic sources. ISM masses estimated for the ALMA-detected sources are 9.9<log(M_ISM_/M_{sun}_)<11.75 assuming a dust temperature of 30 K. The cool dust emission is consistent with star formation rates reaching several thousand M_{sun}_/yr, depending on the assumed dust temperature, but we cannot rule out the alternative that the AGN powers all the emission in some cases. Our best constrained source has radiative transfer solutions with approximately equal contributions from an obscured AGN and a young (10-15 Myr) compact starburst.
- ID:
- ivo://CDS.VizieR/J/ApJ/827/142
- Title:
- ALMA observations of GKM stars in Upper Sco
- Short Name:
- J/ApJ/827/142
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present ALMA observations of 106 G-, K-, and M-type stars in the Upper Scorpius OB Association hosting circumstellar disks. With these data, we measure the 0.88mm continuum and ^12^CO J=3-2 line fluxes of disks around low-mass (0.14-1.66M_{sun}_) stars at an age of 5-11Myr. Of the 75 primordial disks in the sample, 53 are detected in the dust continuum and 26 in CO. Of the 31 disks classified as debris/evolved transitional disks, five are detected in the continuum and none in CO. The lack of CO emission in approximately half of the disks with detected continuum emission can be explained if CO is optically thick but has a compact emitting area (<~40au), or if the CO is heavily depleted by a factor of at least ~1000 relative to interstellar medium abundances and is optically thin. The continuum measurements are used to estimate the dust mass of the disks. We find a correlation between disk dust mass and stellar host mass consistent with a power-law relation of M_dust_{propto}M_*_^1.67+/-0.37^. Disk dust masses in Upper Sco are compared to those measured in the younger Taurus star-forming region to constrain the evolution of disk dust mass. We find that the difference in the mean of log(M_dust_/M*) between Taurus and Upper Sco is 0.64+/-0.09, such that M_dust_/M* is lower in Upper Sco by a factor of ~4.5.
- ID:
- ivo://CDS.VizieR/J/ApJ/768/91
- Title:
- ALMA observations of LESS submm galaxies
- Short Name:
- J/ApJ/768/91
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present an Atacama Large Millimeter/submillimeter Array (ALMA) Cycle 0 survey of 126 submillimeter sources from the LABOCA ECDFS Submillimeter Survey (LESS). Our 870{mu}m survey with ALMA (ALESS) has produced maps ~3x deeper and with a beam area ~200x smaller than the original LESS observations, doubling the current number of interferometrically-observed submillimeter sources. The high resolution of these maps allows us to resolve sources that were previously blended and accurately identify the origin of the submillimeter emission. We discuss the creation of the ALESS submillimeter galaxy (SMG) catalog, including the main sample of 99 SMGs and a supplementary sample of 32 SMGs. We find that at least 35% (possibly up to 50%) of the detected LABOCA sources have been resolved into multiple SMGs, and that the average number of SMGs per LESS source increases with LESS flux density. Using the (now precisely known) SMG positions, we empirically test the theoretical expectation for the uncertainty in the single-dish source positions. We also compare our catalog to the previously predicted radio/mid-infrared counterparts, finding that 45% of the ALESS SMGs were missed by this method. Our ~1.6" resolution allows us to measure a size of ~9kpcx5kpc for the rest-frame ~300{mu}m emission region in one resolved SMG, implying a star formation rate surface density of 80M_{sun}_/yr/kpc2, and we constrain the emission regions in the remaining SMGs to be <10kpc. As the first statistically reliable survey of SMGs, this will provide the basis for an unbiased multiwavelength study of SMG properties.
- ID:
- ivo://CDS.VizieR/J/ApJ/894/L14
- Title:
- ALMA obs. of massive clouds in the CMZ
- Short Name:
- J/ApJ/894/L14
- Date:
- 19 Jan 2022 13:10:58
- Publisher:
- CDS
- Description:
- We report Atacama Large Millimeter/submillimeter Array (ALMA) Band 6 continuum observations of 2000au resolution toward four massive molecular clouds in the Central Molecular Zone of the Galaxy. To study gas fragmentation, we use the dendrogram method to identify cores as traced by the dust continuum emission. The four clouds exhibit different fragmentation states at the observed resolution despite having similar masses at the cloud scale (~1-5pc). Assuming a constant dust temperature of 20K, we construct core mass functions of the clouds and find a slightly top-heavy shape as compared to the canonical initial mass function, but we note several significant uncertainties that may affect this result. The characteristic spatial separation between the cores as identified by the minimum spanning tree method, ~10^4^au, and the characteristic core mass, 1-7M_{sun}_, are consistent with predictions of thermal Jeans fragmentation. The three clouds showing fragmentation may be forming OB associations (stellar mass ~10^3^M_{sun}_). None of the four clouds under investigation seem to be currently able to form massive star clusters like the Arches and the Quintuplet (>~10^4^M_{sun}_), but they may form such clusters by further gas accretion onto the cores.
- ID:
- ivo://CDS.VizieR/J/ApJ/860/82
- Title:
- ALMA obs. of polarization in the IM Lup disk
- Short Name:
- J/ApJ/860/82
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present 870{mu}m ALMA observations of polarized dust emission toward the Class II protoplanetary disk IM Lup. We find that the orientation of the polarized emission is along the minor axis of the disk, and that the value of the polarization fraction increases steadily toward the center of the disk, reaching a peak value of ~1.1%. All of these characteristics are consistent with models of self-scattering of submillimeter-wave emission from an optically thin inclined disk. The distribution of the polarization position angles across the disk reveals that, while the average orientation is along the minor axis, the polarization orientations show a significant spread in angles; this can also be explained by models of pure scattering. We compare the polarization with that of the Class I/II source HL Tau. A comparison of cuts of the polarization fraction across the major and minor axes of both sources reveals that IM Lup has a substantially higher polarization fraction than HL Tau toward the center of the disk. This enhanced polarization fraction could be due a number of factors, including higher optical depth in HL Tau, or scattering by larger dust grains in the more evolved IM Lup disk. However, models yield similar maximum grain sizes for both HL Tau (72{mu}m) and IM Lup (61{mu}m, this work). This reveals continued tension between grain-size estimates from scattering models and from models of the dust emission spectrum, which find that the bulk of the (unpolarized) emission in disks is most likely due to millimeter-sized (or even centimeter-sized) grains.
