* Astronomy

Members Login

Post Info

TOPIC: Rho Ophiuchi IRS48

Blobrana

L

Posts: 131433

Date: Jun 17 05:06 2013

Oph IRS 48	Permalink

Title: A Major Asymmetric Dust Trap in a Transition Disk Authors: Nienke van der Marel (1), Ewine F. van Dishoeck (1,2), Simon Bruderer (2), Til Birnstiel (3), Paola Pinilla (4), Cornelis P. Dullemond (4), Tim A. van Kempen (1,5), Markus Schmalzl (1), Joanna M. Brown (3), Gregory J. Herczeg (6), Geoffrey S. Mathews (1), Vincent Geers (7) ((1) Leiden Observatory, (2) Max-Planck-Institut für Extraterrestrische Physik, (3) Harvard-Smithsonian Center for Astrophysics, (4) Heidelberg University, Institute for Theoretical Astrophysics (5) Joint ALMA Offices, (6) Kavli Institute for Astronomy and Astrophysics, (7) Dublin Institute for Advanced Studies) The statistics of discovered exoplanets suggest that planets form efficiently. However, there are fundamental unsolved problems, such as excessive inward drift of particles in protoplanetary disks during planet formation. Recent theories invoke dust traps to overcome this problem. We report the detection of a dust trap in the disk around the star Oph IRS 48 using observations from the Atacama Large Millimetre/submillimetre Array (ALMA). The 0.44-millimeter-wavelength continuum map shows high-contrast crescent-shaped emission on one side of the star originating from millimetre-sized grains, whereas both the mid-infrared image (micrometer-sized dust) and the gas traced by the carbon monoxide 6-5 rotational line suggest rings centred on the star. The difference in distribution of big grains versus small grains/gas can be modelled with a vortex-shaped dust trap triggered by a companion. Read more (1179kb, PDF) __________________

Blobrana

L

Posts: 131433

Date: Jun 7 04:15 2013

Oph-IRS 48	Permalink

New observations of a dust trap around a young star solve long-standing planet formation mystery Astronomers using the new Atacama Large Millimeter/submillimeter Array (ALMA) have imaged a region around a young star where dust particles can grow by clumping together. This is the first time that such a dust trap has been clearly observed and modelled. It solves a long-standing mystery about how dust particles in discs grow to larger sizes so that they can eventually form comets, planets and other rocky bodies. The results are published in the journal Science on 7 June 2013. Astronomers now know that planets around other stars are plentiful. But they do not fully understand how they form and there are many aspects of the formation of comets, planets and other rocky bodies that remain a mystery. However, new observations exploiting the power of ALMA are now answering one of the biggest questions: how do tiny grains of dust in the disc around a young star grow bigger and bigger - to eventually become rubble, and even boulders well beyond a metre in size? Read more __________________

Blobrana

L

Posts: 131433

Date: Sep 11 11:16 2012

Ophiuchi IRS 48	Permalink

Title: Matryoshka Holes: Nested Emission Rings in the Transitional Disk Oph IRS 48 Authors: Joanna M. Brown, Katherine A. Rosenfeld, Sean M. Andrews, David J. Wilner, Ewine F. van Dishoeck The processes that form transition disks - disks with depleted inner regions - are not well understood; possible scenarios include planet formation, grain growth and photoevaporation. Disks with spatially resolved dust holes are rare, but, in general, even less is known about the gas structure. The disk surrounding A0 star Oph IRS 48 in the nearby Rho Ophiuchus region has a 30 AU radius hole previously detected in the 18.7 micron dust continuum and in warm CO in the 5 micron fundamental ro-vibrational band. We present here Submillimeter Array 880 micron continuum imaging resolving an inner hole. However, the radius of the hole in the millimetre dust is only 13 AU, significantly smaller than measured at other wavelengths. The nesting structure of the disk is counter-intuitive, with increasingly large radii rings of emission seen in the millimetre dust (12.9 +1.7/-3.4 AU), 5 micron CO (30 AU) and 18.7 micron dust (peaking at 55 AU). We discuss possible explanations for this structure, including self-shadowing that cools the disk surface layers, photodissociation of CO, and photoevaporation. However, understanding this unusual disk within the stringent multi-wavelength spatial constraints will require further observations to search for cold atomic and molecular gas. Read more (347kb, PDF) __________________

Blobrana

L

Posts: 131433

Date: Oct 11 01:55 2011

Rho Ophiuchi IRS48	Permalink

Title: A 30 AU radius CO gas hole in the disk around the Herbig Ae star Oph IRS 48 Authors: Joanna M. Brown, Gregory J. Herczeg, Klaus M. Pontoppidan, Ewine F. van Dishoeck The physical processes leading to the disappearance of disks around young stars are not well understood. A subclass of transitional disks, the so-called cold disks with large inner dust holes, provide a crucial laboratory for studying disk dissipation processes. IRS 48 has a 30 AU radius hole previously measured from dust continuum imaging at 18.7 micron. Using new optical spectra, we determine that IRS 48 is a pre-main sequence A0 star. In order to characterie this disk's gas distribution, we obtained AO-assisted VLT CRIRES high resolution (R ~100,000) spectra of the CO fundamental rovibrational band at 4.7 micron. All CO emission, including that from isotopologues and vibrationally excited molecules, is off-source and peaks at 30 AU. The gas is thermally excited to a rotational temperature of 260 K and is also strongly UV pumped, showing a vibrational excitation temperature of ~5000 K. We model the kinematics and excitation of the gas and posit that the CO emission arises from the dust hole wall. Prior imaging of UV-excited PAH molecules, usually a gas tracer, within the hole makes the large CO hole even more unexpected. Read more (795kb, PDF) Position (J2000): R.A. 16 27 37.193 \| Dec. -24° 30' 34.83'' __________________

Page 1 of 1 sorted by

Create your own FREE Forum
Report Abuse