L1448 Irs2e: A Candidate First Hydrostatic Core

Chen, Xuepeng; Arce, Héctor G.; Zhang, Qizhou; Bourke, Tyler L.; Launhardt, R.; Schmalz, Markus; Henning, Thomas

doi:10.1088/0004-637x/715/2/1344

Cited by 96 publications

(119 citation statements)

References 43 publications

(57 reference statements)

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“…We note that Chen et al (2010) proposed L1448 IRS2E as a candidate first hydrostatic core based on its low bolometric luminosity (L bol < 0.1 L , with no Spitzer detection at 70 μm and below) and their detection of a compact outflow. Magnetohydrodynamical simulations do predict that a first core may drive an outflow but they predict that it should be slow (a couple of km s −1 at most, see, e.g., Tomisaka 2002;Machida et al 2008).…”

Section: Evolutionary State Of Cha-mms1 and Cha-mms2mentioning

confidence: 85%

The end of star formation in Chamaeleon I?

Беллоче

Schüller

Parise

et al. 2011

A&A

144

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Context. Chamaeleon I is the most active region in terms of star formation in the Chamaeleon molecular cloud complex. Although it is one of the nearest low-mass star forming regions, its population of prestellar and protostellar cores is not known and a controversy exists concerning its history of star formation. Aims. Our goal is to search for prestellar and protostellar cores and characterize the earliest stages of star formation in this cloud. Methods. We used the bolometer array LABOCA at the APEX telescope to map the cloud in dust continuum emission at 870 μm with a high sensitivity. This deep, unbiased survey was performed based on an extinction map derived from 2MASS data. The 870 μm map is compared with the extinction map and C 18 O observations, and decomposed with a multiresolution algorithm. The extracted sources are analysed by carefully taking into account the spatial filtering inherent in the data reduction process. A search for associations with young stellar objects is performed using Spitzer data and the SIMBAD database. Results. Most of the detected 870 μm emission is distributed in five filaments. We identify 59 starless cores, one candidate first hydrostatic core, and 21 sources associated with more evolved young stellar objects. The estimated 90% completeness limit of our survey is 0.22 M for the starless cores. The latter are only found above a visual extinction threshold of 5 mag. They are less dense than those detected in other nearby molecular clouds by a factor of a few on average, maybe because of the better sensitivity of our survey. The core mass distribution is consistent with the IMF at the high-mass end but is overpopulated at the low-mass end. In addition, at most 17% of the cores have a mass larger than the critical Bonnor-Ebert mass. Both results suggest that a large fraction of the starless cores may not be prestellar in nature. Based on the census of prestellar cores, Class 0 protostars, and more evolved young stellar objects, we conclude that the star formation rate has decreased with time in this cloud. Conclusions. The low fraction of candidate prestellar cores among the population of starless cores, the small number of Class 0 protostars, the high global star formation efficiency, the decrease of the star formation rate with time, and the low mass per unit length of the detected filaments all suggest that we may be witnessing the end of the star formation process in Chamaeleon I.

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Section: Evolutionary State Of Cha-mms1 and Cha-mms2mentioning

confidence: 85%

The end of star formation in Chamaeleon I?

Беллоче

Schüller

Parise

et al. 2011

A&A

144

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“…It should be noted that the higher spatial resolution of IRAC data makes it more likely to have chance associations. In addition, sources with no 24 μm detection, and possibly even those with no 70 μm counterpart, cannot be definitively classified as starless, at least in a low-mass clump (see Chen et al 2010). These kind of sources may in fact represent a stage intermediate between a gravitationally-bound starless clump (i.e., pre-stellar) and a Class 0 protostar, and are difficult to identify.…”

Section: Source and Flux Extraction In The Spire/pacs Mapsmentioning

confidence: 99%

On the shape of the mass-function of dense clumps in the Hi-GAL fields

Olmi

Anglés-Alcázar

Elia

et al. 2013

A&A

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Context. Stars form in dense, dusty clumps of molecular clouds, but little is known about their origin and evolution. In particular, the relationship between the mass distribution of these clumps (also known as the clump mass function or CMF) and the stellar initial mass function (IMF), is still poorly understood. Aims. To discern the "true" shape of the CMF and to better understand how the CMF may evolve toward the IMF, large samples of bona-fide pre-and proto-stellar clumps are required. The sensitive observations of the Herschel Space Observatory (HSO) are now allowing us to look at large clump populations in various clouds with different physical conditions. Methods. We analyze two fields in the Galactic plane mapped by HSO during its science demonstration phase (SDP), as part of the more complete and unbiased Herschel infrared GALactic Plane Survey (Hi-GAL). These fields underwent a source-extraction and flux-estimation pipeline, which allowed us to obtain a sample with thousands of clumps. Starless and proto-stellar clumps were separated using both color and positional criteria to find those coincident with MIPS 24 μm sources. We describe the probability density functions of the power-law and lognormal models that were used to fit the CMFs. For the lognormal model we applied several statistical techniques to the data and compared their results. Results. The CMFs of the two SDP fields show very similar shapes, but very different mass scales. This similarity is confirmed by the values of the best-fit parameters of either the power-law or lognormal model. The power-law model leads to almost identical CMF slopes, whereas the lognormal model shows that the CMFs have similar widths. Conclusions. The similar CMF shape but different mass scale represents an evidence that the overall process of star formation in the two regions is very different. When comparing with the IMF, we find that the width of the IMF is narrower than the measured widths of the CMF in the two SDP fields. This may suggest that an additional mass selection occurs in later stages of gravitational collapse.

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“…VeLLOs, however, appear more evolved than FHSCs with features consistent with Class 0 and I protostars. Furthermore, while several FHSC candidates have been identified recently (e.g., see Enoch et al 2010;Chen et al 2010;Pineda et al 2011;Pezzuto et al 2012), it has proven observationally difficult to distinguish such sources from the young Class 0 protostellar phase. It is therefore currently difficult to identify the very earliest phases of the formation of a protostar.…”

Section: Introductionmentioning

confidence: 99%

AHERSCHELAND APEX CENSUS OF THE REDDEST SOURCES IN ORION: SEARCHING FOR THE YOUNGEST PROTOSTARS

Stutz

Tobin

Stanke³

et al. 2013

ApJ

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175

357

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We perform a census of the reddest, and potentially youngest, protostars in the Orion molecular clouds using data obtained with the PACS instrument on board the Herschel Space Observatory and the LABOCA and SABOCA instruments on APEX as part of the Herschel Orion Protostar Survey (HOPS). A total of 55 new protostar candidates are detected at 70 μm and 160 μm that are either too faint (m 24 > 7 mag) to be reliably classified as protostars or undetected in the Spitzer/MIPS 24 μm band. We find that the 11 reddest protostar candidates with log λF λ 70/λF λ 24 > 1.65 are free of contamination and can thus be reliably explained as protostars. The remaining 44 sources have less extreme 70/24 colors, fainter 70 μm fluxes, and higher levels of contamination. Taking the previously known sample of Spitzer protostars and the new sample together, we find 18 sources that have log λF λ 70/λF λ 24 > 1.65; we name these sources "PACS Bright Red sources," or PBRs. Our analysis reveals that the PBR sample is composed of Class 0 like sources characterized by very red spectral energy distributions (SEDs; T bol < 45 K) and large values of sub-millimeter fluxes (L smm /L bol > 0.6%). Modified blackbody fits to the SEDs provide lower limits to the envelope masses of 0.2-2 M and luminosities of 0.7-10 L . Based on these properties, and a comparison of the SEDs with radiative transfer models of protostars, we conclude that the PBRs are most likely extreme Class 0 objects distinguished by higher than typical envelope densities and hence, high mass infall rates.

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L1448 Irs2e: A Candidate First Hydrostatic Core

Cited by 96 publications

References 43 publications

The end of star formation in Chamaeleon I?

The end of star formation in Chamaeleon I?

On the shape of the mass-function of dense clumps in the Hi-GAL fields

AHERSCHELAND APEX CENSUS OF THE REDDEST SOURCES IN ORION: SEARCHING FOR THE YOUNGEST PROTOSTARS

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