5 research outputs found
Near-Infrared Observations of Outflows and YSOs in the Massive Star-Forming Region AFGL 5180
Methods: Broad- and narrow-band imaging of AFGL 5180 was made in the NIR with
the LBT, in both seeing-limited (\sim0.5\arcsec) and high angular resolution
(\sim0.09\arcsec) Adaptive Optics (AO) modes, as well as with HST. Archival
ALMA continuum data was also utilized.
Results: At least 40 jet knots were identified via NIR emission from H
and [FeII] tracing shocked gas. Bright jet knots outflowing from the central
most massive protostar, S4, are detected towards the east of the source and are
resolved in fine detail with the AO imaging. Additional knots are distributed
throughout the field, likely indicating the presence of multiple driving
sources. Sub-millimeter sources detected by ALMA are shown to be grouped in two
main complexes, AFGL 5180 M and a small cluster \sim15\arcsec to the south,
AFGL 5180 S. From our NIR continuum images we identify YSO candidates down to
masses of . Combined with the sub-mm sources, this yields a
surface number density of such YSOs of within a
projected radius of about 0.1 pc. Such a value is similar to those predicted by
models of both Core Accretion from a turbulent clump environment and
Competitive Accretion. The radial profile of is relatively flat on scales
out to 0.2~pc, with only modest enhancement around the massive protostar inside
0.05~pc.
Conclusions: This study demonstrates the utility of high-resolution NIR
imaging, in particular with AO, for detecting outflow activity and YSOs in
distant regions. The presented images reveal the complex morphology of
outflow-shocked gas within the large-scale bipolar flow of a massive protostar,
as well as clear evidence for several other outflow driving sources in the
region. Finally, this work presents a novel approach to compare the observed
YSO surface number density from our study against different models of massive
star formation.Comment: Accepted to Astronomy & Astrophysics (A&A
Observations of edge-on protoplanetary disks with ALMA
Aims. We aim to study vertical settling and radial drift of dust in protoplanetary disks from a different perspective: an edge-on view. An estimation of the amplitude of settling and drift is highly relevant to understanding planet formation.
Methods. We analyze a sample of 12 HST-selected edge-on protoplanetary disks (i.e., seen with high inclinations) for which the vertical extent of the emission layers can be constrained directly. We present ALMA high angular resolution continuum images (~0.1âČâČ) of these disks at two wavelengths, 0.89 and 2.06 mm (respectively ALMA bands 7 and 4), supplemented with archival band 6 data (1.33 mm) where available.
Results. Several sources show constant brightness profiles along their major axis with a steep drop at the outer edges. Two disks have central holes with additional compact continuum emission at the location of the central star. For most sources, the millimeter continuum emission is more compact than the scattered light, both in the vertical and radial directions. Six sources are resolved along their minor axis in at least one millimetric band, providing direct information on the vertical distribution of the millimeter grains. For the second largest disk of the sample, Tau 042021, the significant difference in vertical extent between band 7 and band 4 suggests efficient size-selective vertical settling of large grains. Furthermore, the only Class I object in our sample shows evidence of flaring in the millimeter. Along the major axis, all disks are well resolved. Four of them are larger in band 7 than in band 4 in the radial direction, and three have a similar radial extent in all bands. These three disks are also the ones with the sharpest apparent edges (between 80% and 20% of the peak flux, Îrâr ~ 0.3), and two of them are binaries. For all disks, we also derive the millimeter brightness temperature and spectral index maps. We find that all edge-on disks in our sample are likely optically thick and that the dust emission reveals low brightness temperatures in most cases (brightness temperatures â€10 K). The integrated spectral indices are similar to those of disks at lower inclination.
Conclusions. The comparison of a generic radiative transfer disk model with our data shows that at least three disks are consistent with a small millimeter dust scale height, of a few au (measured at r = 100 au). This is in contrast with the more classical value of hg ~ 10 au derived from scattered light images and from gas line measurements. These results confirm, by direct observations, that large (millimeter) grains are subject to significant vertical settling in protoplanetary disks
Manifold Connections
This paper focuses on eastern Indonesia, and in particular on the Minahasa region of northern Sulawesi. It examines the links of this region with others in the archipelago, as well as with the state, from the early modern period through to the present, and tests the usefulness of the concepts of âcentreâ and âperipheryâ in understanding the nature of those links. A centreâperiphery relationship is commonly defined in terms of geography, economy or power relations, but, as the paper argues, the definition can also rest on cultural or social factors. The paper also suggests the possibility of the simultaneous or successive existence of several centres and many peripheries.info:eu-repo/semantics/publishedVersio