A uniform CO survey of the molecular clouds in Orion  and Monoceros

Wilson, B. A.; Dame, T. M.; Masheder, M. R. W.; Thaddeus, P.

doi:10.1051/0004-6361:20035943

Cited by 157 publications

(227 citation statements)

References 42 publications

Supporting

Mentioning

209

Contrasting

Order By: Relevance

“…The Orion B9 region is likely to be influenced by the massive stars of the nearby Ori OB 1b group. This explains the origin of the low-velocity material in the southern parts of Orion B (Wilson et al 2005). Moreover, this interaction process could have led to formation of dense filaments, from which the dense cores were fragmented out by the action of gravitational instability.…”

Section: Discussionmentioning

confidence: 95%

Physical properties of dense cores in Orion B9

Miettinen

Harju

Haikala

et al. 2010

A&A

View full text Add to dashboard Cite

Aims. We aim to determine the physical and chemical properties of the starless and protostellar cores in Orion B9, which represents a relatively quiescent star-forming region in Orion B. Methods. We observed the NH 3 (J, K) = (1, 1) and (2, 2) inversion lines and the N 2 H + (3−2) rotational lines, with the Effelsberg 100-m and APEX telescopes, respectively, towards the submillimetre peak positions in Orion B9. These data are used in conjunction with our APEX/LABOCA 870 μm dust continuum data of the region. Results. The gas kinetic temperature in the cores derived from the NH 3 data is between ∼9.4−13.9 K. The non-thermal velocity dispersion is subsonic in most of the cores. The non-thermal linewidth in protostellar cores appears to increase with increasing bolometric luminosity. The core masses, ∼2−8 M , are very likely drawn from the same parent distribution as the core masses in Orion B North. Based on the virial parameter analysis, starless cores in the region are likely to be gravitationally bound, and thus prestellar. Some of the cores have a lower radial velocity than the systemic velocity of the region, suggesting that they are members of the "low-velocity part" of Orion B. The observed core-separation distances deviate from the corresponding random-like model distributions. The distances between the nearest neighbours are comparable to the thermal Jeans length. The fractional abundances of NH 3 and N 2 H + in the cores are ∼1.5−9.8 × 10 −8 and ∼0.2−5.9 × 10 −10 , respectively. The NH 3 abundance appears to decrease with increasing H 2 column and number densities. The NH 3 /N 2 H + column density ratio is larger in starless cores than in cores with embedded protostars. Conclusions. The core population in Orion B9 is comparable in physical properties to those in nearby low-mass star-forming regions. The Orion B9 cores also seem to resemble cores found in isolation rather than those associated with clusters. Moreover, because the cores may not be randomly distributed within the region (contrary to what was suggested in our Paper I), it is unclear whether the origin of cores could be explained by turbulent fragmentation. On the other hand, many of the core properties conform to the picture of dynamic core evolution. The Orion B9 region has probably been influenced by the feedback from the nearby Ori OB 1b group, and the fragmentation of the parental cloud into cores could be caused by gravitational instability.

show abstract

Section: Discussionmentioning

confidence: 95%

Physical properties of dense cores in Orion B9

Miettinen

Harju

Haikala

et al. 2010

A&A

View full text Add to dashboard Cite

show abstract

“…44-16.38 This field corresponds to NGC 2149 in the Orion molecular complex. Wilson et al (2005) propose that this cloud makes the connection between Orion A and the Southern Filament, and therefore has a distance of 425 pc, intermediate between these two structures. We adopt this estimate with an uncertainty of 100 pc corresponding to the uncertainties on the distances to Orion A and the Southern Filament.…”

Section: D85 G21537-304mentioning

confidence: 97%

Galactic cold cores

Montillaud

Juvela

Rivera-Ingraham

et al. 2015

A&A

160

View full text Add to dashboard Cite

Context. For the project Galactic cold cores, Herschel photometric observations were carried out as a follow-up of cold regions of interstellar clouds previously identified with the Planck satellite. The aim of the project is to derive the physical properties of the population of cold sources and to study its connection to ongoing and future star formation. Aims. We build a catalogue of cold sources within the clouds in 116 fields observed with the Herschel PACS and SPIRE instruments. We wish to determine the general physical characteristics of the cold sources and to examine the correlations with their host cloud properties. Methods. From Herschel data, we computed colour temperature and column density maps of the fields. We estimated the distance to the target clouds and provide both uncertainties and reliability flags for the distances. The getsources multiwavelength source extraction algorithm was employed to build a catalogue of several thousand cold sources. Mid-infrared data were used, along with colour and position criteria, to separate starless and protostellar sources. We also propose another classification method based on submillimetre temperature profiles. We analysed the statistical distributions of the physical properties of the source samples. Results. We provide a catalogue of ∼4000 cold sources within or near star forming clouds, most of which are located either in nearby molecular complexes ( 1 kpc) or in star forming regions of the nearby galactic arms (∼2 kpc). About 70% of the sources have a size compatible with an individual core, and 35% of those sources are likely to be gravitationally bound. Significant statistical differences in physical properties are found between starless and protostellar sources, in column density versus dust temperature, mass versus size, and mass versus dust temperature diagrams. The core mass functions are very similar to those previously reported for other regions. On statistical grounds we find that gravitationally bound sources have higher background column densities (median N bg (H 2 ) ∼ 5 × 10 21 cm −2 ) than unbound sources (median N bg (H 2 ) ∼ 3 × 10 21 cm −2 ). These values of N bg (H 2 ) are higher for higher dust temperatures of the external layers of the parent cloud. However, only in a few cases do we find clear N bg (H 2 ) thresholds for the presence of cores. The dust temperatures of cloud external layers show clear variations with galactic location, as may the source temperatures. Conclusions. Our data support a more complex view of star formation than in the simple idea of a column density threshold. They show a clear influence of the surrounding UV-visible radiation on how cores distribute in their host clouds with possible variations on the Galactic scale.

show abstract

“…We adopt a distance of 450 pc for both L1630N and L1641 (Genzel et al 1981;Anthony-Twarog 1982;Maddalena et al 1986;Wilson et al 2005). Note that we have implicitly corrected for extinction by calculating the bolometric luminosities in this way.…”

Section: Hr Diagramsmentioning

confidence: 99%

Star and protoplanetary disk properties in Orion's suburbs

Fang

Boekel²,

Wang³

et al. 2009

A&A

253

401

View full text Add to dashboard Cite

Context. Knowledge of the evolution of circumstellar accretion disks is pivotal to our understanding of star and planet formation; and yet despite intensive theoretical and observational studies, the disk dissipation process is not well understood. Infrared observations of large numbers of young stars, as performed by the Spitzer Space Telescope, may advance our knowledge of this inherently complex process. While infrared data reveal the evolutionary status of the disk, they hold little information on the properties of the central star and the accretion characteristics. Aims. Existing 2MASS and Spitzer archive data of the Lynds 1630N and 1641 clouds in the Orion GMC provide disk properties of a large number of young stars. We wish to complement these data with optical data that provide the physical stellar parameters and accretion characteristics. Methods. We performed a large optical spectroscopic and photometric survey of the aforementioned clouds. Spectral types, as well as accretion and outflow characteristics, are derived from our VLT/VIMOS spectra. Optical SDSS and CAHA/LAICA imaging was combined with 2MASS, Spitzer IRAC, and MIPS imaging to obtain spectral energy distributions from 0.4 to 24 μm. Reddened model atmospheres were fitted to the optical/NIR photometric data, keeping T eff fixed at the spectroscopic value. Mass and age estimates of individual objects were made through placement in the HR diagram and comparison to several sets of pre-main sequence evolutionary tracks. Results. We provide a catalog of 132 confirmed young stars in L1630N and 267 such objects in L1641. We identify 28 transition disk systems, 20 of which were previously unknown, as well as 42 new transition disk candidates for which we have broad-band photometry but no optical spectroscopy. We give mass and age estimates for the individual stars, as well as equivalent widths of optical emission lines, the extinction, and measures of the evolutionary state of the circumstellar dusty disk. We estimate mass accretion ratesṀ acc from the equivalent widths of the Hα, Hβ, and He I 5876 Å emission lines, and find a dependence ofṀ acc ∝ M α * , with α ∼ 3.1 in the subsolar mass range that we probe. An investigation of a large literature sample of mass accretion rate estimates yields a similar slope of α ∼ 2.8 in the subsolar regime, but a shallower slope of α ∼ 2.0 if the whole mass range of 0.04 M ≤ M * ≤ 5 M is included. The fraction of stars with transition disks that show significant accretion activity is relatively low compared to stars with still optically thick disks (26 ± 11% vs. 57 ± 6%, respectively). However, those transition disks that do show significant accretion have the same median accretion rate as normal optically thick disks of 3−4 × 10 −9 M yr −1 . Analyzing the age distribution of various populations, we find that the ages of the CTTSs and the WTTSs with disks are statistically indistinguishable, the WTTSs without disks are significantly older than the CTTSs, and the ages of the transition disks and the WTTSs wi...

show abstract

A uniform CO survey of the molecular clouds in Orion and Monoceros

Cited by 157 publications

References 42 publications

Physical properties of dense cores in Orion B9

Physical properties of dense cores in Orion B9

Galactic cold cores

Star and protoplanetary disk properties in Orion's suburbs

Contact Info

Product

Resources

About