Engineering topics

Zinnecker, Hans

Publications and source records attributed to Zinnecker, Hans.

7 records

DOE OSTI2021

The Stellar Content of H72.97-69.39, a Potential Super Star Cluster in the Making

Young massive clusters and super star clusters (SSCs) represent an extreme mode of star formation. Far-infrared imaging of the Magellanic Clouds has identified one potential embedded SSC, HSO BMHERICC J72.971176-69.391112 (H72.97-69.39 in short), in the southwest outskirts of the Large Magellanic Cloud. We present Gemini Flamingos 2 and GSAOI near-infrared imaging of a 3′ × 3′ region around H72.97-69.39 in order to characterize the stellar content of the cluster. The stellar content is probed down to 1.5 M {sub ⊙}. We find substantial dust extinction across the cluster region, extending up to A {sub K} of 3. Deeply embedded stars are associated with ALMA-detected molecular gas suggesting that star formation is ongoing. The high spatial resolution of the GSAOI data allows identification of the central massive object associated with the {sup 13}CO ALMA observations and detection of fainter low-mass stars around the H30α ALMA source. The morphology of the molecular gas and the nebulosity from adjacent star formation suggest they have interacted covering a region of several parsecs. The total stellar content in the cluster is estimated from the intermediate- and high-mass stellar content to be at least 10,000 M {sub ⊙}, less than R136 with up to 100,000 M {sub ⊙} within 4.7 pc radius, but places it in the regime of an SSC. Based on the extinction determination of individual stars we estimate a molecular gas mass in the vicinity of H72.97-69.39 of 6600 M {sub ⊙}, suggesting more star formation can be expected.

74 ATOMIC AND MOLECULAR PHYSICS↗

DOE OSTI2017

The ALMA View of the OMC1 Explosion in Orion

Most massive stars form in dense clusters where gravitational interactions with other stars may be common. The two nearest forming massive stars, the BN object and Source I, located behind the Orion Nebula, were ejected with velocities of ∼29 and ∼13 km s{sup −1} about 500 years ago by such interactions. This event generated an explosion in the gas. New ALMA observations show in unprecedented detail, a roughly spherically symmetric distribution of over a hundred {sup 12}CO J = 2−1 streamers with velocities extending from V {sub LSR} = −150 to +145 km s{sup −1}. The streamer radial velocities increase (or decrease) linearly with projected distance from the explosion center, forming a “Hubble Flow” confined to within 50″ of the explosion center. They point toward the high proper-motion, shock-excited H{sub 2} and [Fe ii] “fingertips” and lower-velocity CO in the H{sub 2} wakes comprising Orion's “fingers.” In some directions, the H{sub 2} “fingers” extend more than a factor of two farther from the ejection center than the CO streamers. Such deviations from spherical symmetry may be caused by ejecta running into dense gas or the dynamics of the N -body interaction that ejected the stars and produced the explosion. This ∼10{sup 48} erg event may have been powered by the release of gravitational potential energy associated with the formation of a compact binary or a protostellar merger. Orion may be the prototype for a new class of stellar explosiozn responsible for luminous infrared transients in nearby galaxies.

79 ASTRONOMY AND ASTROPHYSICS↗

DOE OSTI2013

KECK ADAPTIVE OPTICS OBSERVATIONS OF THE PROTOSTELLAR DISK AROUND RADIO SOURCE I IN THE ORION KLEINMANN-LOW NEBULA

We have made the first detection of a near-infrared counterpart associated with the disk around Radio Source ''I'', a massive protostar in the Kleinmann-Low nebula in Orion, using imaging with laser guide star adaptive optics on the Keck II telescope. The infrared emission is evident in images acquired using L' (3.8 {mu}m) and Ms (4.7 {mu}m) filters and is not detectable at K' (2.1 {mu}m). The observed morphology strongly suggests that we are seeing some combination of scattered and thermal light emanating from the disk. The disk is also manifest in the L'/Ms flux ratio image. We interpret the near-infrared emission as the illuminated surface of a nearly edge-on disk, oriented so that only the northern face is visible; the opposite surface remains hidden by the disk. We do not see infrared radiation associated directly with the star proposed to be associated with Source ''I''. The data also suggest that there is a cavity above and below the disk that is oriented perpendicular to the disk and is sculpted by the known, strong outflow from the inner disk of Source I. We compare our data to models of a protostar with a surrounding disk, envelope, and wind-blown cavity in order to elucidate the nature of the disk around Radio Source I.

79 ASTRONOMY AND ASTROPHYSICS↗

DOE OSTI2012

FIRST SCIENCE OBSERVATIONS WITH SOFIA/FORCAST: 6-37 {mu}m IMAGING OF THE CENTRAL ORION NEBULA

We present new mid-infrared images of the central region of the Orion Nebula using the newly commissioned Stratospheric Observatory For Infrared Astronomy airborne telescope and its 5-40 {mu}m camera FORCAST. The 37.1 {mu}m images represent the highest resolution observations ({approx}<4'') ever obtained of this region at these wavelengths. After BN/KL (which is described in a separate paper in this issue), the dominant source at all wavelengths except 37.1 {mu}m is the Ney-Allen Nebula, a crescent-shaped extended source associated with {theta}{sup 1} D Ori. The morphology of the Ney-Allen nebula in our images is consistent with the interpretation that it is ambient dust swept up by the stellar wind from {theta}{sup 1} D Ori, as suggested by Smith et al. in 2005. Our observations also reveal emission from two 'proplyds' (proto-planetary disks), and a few embedded young stellar objects (YSOs; IRc 9, and OMC1-S IRS1, 2, and 10). The spectral energy distribution for IRc 9 is presented and fitted with standard YSO models from Robitaille et al. in 2007 to constrain the total luminosity, disk size, and envelope size. The diffuse, nebular emission we observe at all FORCAST wavelengths is most likely from the background photodissociation region (PDR) and shows structure that coincides roughly with H{alpha} and [N II] emission. We conclude that the spatial variations in the diffuse emission are likely due to undulations in the surface of the background PDR.

79 ASTRONOMY AND ASTROPHYSICS↗

DOE OSTI2012

FIRST SCIENCE OBSERVATIONS WITH SOFIA/FORCAST: 6-37 {mu}m IMAGING OF ORION BN/KL

The Becklin-Neugebauer/Kleinmann-Low (BN/KL) region of the Orion Nebula is the nearest region of high-mass star formation in our galaxy. As such, it has been the subject of intense investigation at a variety of wavelengths, which have revealed it to be brightest in the infrared to submillimeter wavelength regime. Using the newly commissioned SOFIA airborne telescope and its 5-40 {mu}m camera FORCAST, images of the entire BN/KL complex have been acquired. The 31.5 and 37.1 {mu}m images represent the highest resolution observations ({approx}<4'') ever obtained of this region at these wavelengths. These observations reveal that the BN object is not the dominant brightness source in the complex at wavelengths {>=} 31.5 {mu}m and that this distinction goes instead to the source IRc4. It was determined from these images and derived dust color temperature maps that IRc4 is also likely to be self-luminous. A new source of emission has also been identified at wavelengths {>=} 31.5 {mu}m that coincides with the northeastern outflow lobe from the protostellar disk associated with radio source I.

79 ASTRONOMY AND ASTROPHYSICS↗

NASA NTRS1993

Young low mass stars in the vicinity of Sigma Scorpii

The region near Sigma Scorpii, a member of the Sco-Cen OB association, is examined for signs of recent star formation. Thirteen candidate young stellar objects are identified over an 80 x 80 arcmin region centered on Sigma Sco using the Point source Catalog and a recent survey for H-alpha emission-line stars. Near-infrared photometry, improved IRAS fluxes, and optical spectra are used to determine the nature of these objects. Four definite young stars are revealed, as well as one additional such object that fell just outside of the present target region. These stars, all of spectral type K or M, are argued to have formed in the vicinity of the B1 giant star Sigma Scorpii and to represent a subsample of the low-mass members of the association.

Meyer, Michael R.↗

NASA NTRS1993

The initial stellar population

Current theories for the origin of stellar masses and the initial mass function are surveyed, with emphasis on the formation of stars in clusters, and the possibility that several different formation mechanisms are at work in the Galaxy. Models are presented for the evolution of the 2.2-micron premain-sequence luminosity function of a young coeval star cluster, and the implications the results have for the conversion of an observed luminosity function into the underlying mass function are discussed. A description of theories which allow spectral energy distributions of young stellar objects to be used as diagnostics of their evolutionary states is given. The question of the existence of substellar objects (brown dwarfs) in nearby young clusters and regions of star formation is addressed.

Zinnecker, Hans↗