A search for T Tauri stars in high-latitude molecular clouds. 2: The IRAS Faint Source Survey catalog

Magnani, L.; Caillault, J. P.; Buchalter, Ari; Beichman, Charles

doi:10.1086/192116

Cited by 40 publications

(18 citation statements)

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“…According to Pottasch et al (1988), about 20% of the most evolved OH/IR stars have colours similar to young PNe. However, T-Tauri stars are also found in this area of the IRAS diagram (Magnani et al 1995).…”

Section: Iphas and 2massmentioning

confidence: 90%

New young planetary nebulae in IPHAS

Viironen¹,

Mampaso²,

Corradi

et al. 2009

A&A

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Aims. We search for very small-diameter galactic planetary nebulae (PNe) representing the earliest phases of PN evolution. The IPHAS catalogue of Hα-emitting stars provides a useful basis for this study since all sources present in this catalogue must be of small angular diameter. Results. We present a total of 83 PN candidates. We were able to obtain spectra or find the classification from the literature for 35 candidates. Five of these objects are likely to be new PNe, including one large bipolar PN discovered serendipitously close to an emission-line star. PN distances deduced from extinction-distance relations based on IPHAS field-star photometry are presented for the first time. These yield distance estimates for our objects in the range 2 kpc and 6 kpc. From the data in hand, we conclude that four of the discovered objects are probably young PNe.

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Section: Iphas and 2massmentioning

confidence: 90%

New young planetary nebulae in IPHAS

Viironen¹,

Mampaso²,

Corradi

et al. 2009

A&A

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“…They are in general not gravitationally bound (Dobbs et al, 2011), and are surrounded by a layer of less dense atomic gas which shields the molecules from the interstellar UV radiation field that is capable of dissociating molecules and leads to a low rate of heating by external radiation (Elmegreen, 1993). Giant molecular clouds may contain several sites of star formation, and while smaller molecular clouds with masses 10 2 M may also form stars, their contribution to the total star formation rate in the Galaxy is negligible (Magnani et al, 1995).…”

Section: Molecular Cloudsmentioning

confidence: 99%

Star Formation and the Hall Effect

Wardle

2004

Astrophysics and Space Science

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Magnetic fields play an important role in star formation by regulating the removal of angular momentum from collapsing molecular cloud cores. Hall diffusion is known to be important to the magnetic field behaviour at many of the intermediate densities and field strengths encountered during the gravitational collapse of molecular cloud cores into protostars, and yet its role in the star formation process is not well-studied. This thesis describes a semianalytic self-similar model of the collapse of rotating isothermal molecular cloud cores with both Hall and ambipolar diffusion, presenting similarity solutions that demonstrate that the Hall effect has a profound influence on the dynamics of collapse.Two asymptotic power law similarity solutions to the collapse equations on the inner boundary are derived. The first of these represents a Keplerian disc in which accretion is regulated by the magnetic diffusion; with an appropriate value of the Hall diffusion parameter a stable rotationally-supported disc forms, but when the Hall parameter has the opposite sign disc formation is suppressed by the strong diffusion. The second solution describes the infall when the magnetic braking is so efficient at removing angular momentum from the core that no disc forms and the matter free falls onto the protostar.The full similarity solutions show that the size and sign of the Hall parameter can change the size of the protostellar disc by up to an order of magnitude and the accretion rate onto the protostar by 1.5 × 10 −6 M yr −1 when the ratio of the Hall to ambipolar diffusion parameters moves between the extremes of −0.5 ≤η H /η A ≤ 0.2. These variations (and their dependence upon the orientation of the magnetic field with respect to the axis of rotation) create a preferred handedness to the solutions that could be observed in protostellar cores using next-generation instruments such as ALMA.Hall diffusion also determines the strength of the magnetic diffusion and centrifugal shocks that bound the pseudo and rotationally-supported discs, and can introduce subshocks that further slow accretion onto the protostar. In cores that are not initially rotating Hall diffusion can even induce rotation, which could give rise to disc formation and resolve the magnetic braking catastrophe. The Hall effect clearly influences the dynamics of gravitational collapse and its role in controlling the magnetic braking and radial diffusion of the field would be worth exploring in future numerical simulations of star formation. Statement of CandidateI certify that the work in this thesis, entitled "Star Formation and the Hall Effect", has not previously been submitted for a degree nor has it been submitted as part of requirements for a degree to any other university or institution other than Macquarie University.I also certify that this thesis is an original piece of research and that it has been written by myself. Any help and assistance that I have received in my research work and the preparation of the thesis itself have been appropriatel...

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“…5 of Désert et al (2008). Observations have revealed a number of low mass stars that evidently have formed at high Galactic latitudes (Martin & Kun 1996;Magnani et al 1995;Hearty et al 2000). Furthermore, whereas detection methods based on extinction are biased towards near distances, methods based on emission should, in principle, be able to detect them also at large distances, with some limitation due to resolution, sensitivity and Galactic confusion.…”

Section: Introductionmentioning

confidence: 99%

An all-sky catalogue of cold cores observed withPlanck-HFI: simulation and colour detection algorithms

Montier

Pelkonen

Juvela

et al. 2010

A&A

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Context. Planck will provide an unprecedented view of the (cold dust in both diffuse regions and dense cores and associated gas in the Galaxy), resulting in the observation of a large number of cold objects. Understanding the processes acting at the very earliest stages of star formation requires a detailed study of these cold cores. Aims. We present an algorithm which is able to compile a reliable catalogue of cold cores from the Planck High Frequency Instrument (HFI) data. We construct models of the cold cores and validate the extraction algorithm on simulated Planck data. Methods. We model cold cores along with their warmer envelopes which are then injected into a full sky simulation of Planck HFI data. These cold cores are mostly embedded in the relatively warmer Galactic background, in particular in the plane where there is a high level of confusion. We have developed two detection algorithms which make use of the colour of the cores rather than simply extracting compact sources from the individual frequency maps. The cold sources present a relative emission excess at wavelengths longer than 350 μm (i.e. 857 GHz), and thus provide the necessary signature to separate them from the diffuse Galactic emission and warmer cores. Furthermore, using an optimised photometry algorithm for embedded cold sources, reliable fluxes can be extracted. Results. We recover nearly 3% of our input sources, with 60% completeness at high latitude. This suggests that we will be able to compile a catalogue of nearly 5000 objects over the entire sky with a reliability of 98%. These detections cover the entire simulated mass range from 0.4 to 10 000 solar masses and cover the entire sky, including a small number of sources on the far side of the Galaxy. Conclusions. This algorithm is ready to be applied on Planck HFI data, and will be able to produce a reliable catalogue of sources ready for follow up observations, in particular for the Herschel open-time key-program on Galactic cold cores.

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A search for T Tauri stars in high-latitude molecular clouds. 2: The IRAS Faint Source Survey catalog

Cited by 40 publications

References 0 publications

New young planetary nebulae in IPHAS

New young planetary nebulae in IPHAS

Star Formation and the Hall Effect

An all-sky catalogue of cold cores observed withPlanck-HFI: simulation and colour detection algorithms

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