Results from HOPS: A multiwavelength census of Orion protostars

Fischer, William J.; Megeath, S. Thomas; Stutz, Amelia M.; Tobin, John J.; Ali, B.; Stanke, T.; Osorio, M. R. Zapatero; Furlan, Elise

doi:10.1002/asna.201211761

Cited by 36 publications

(35 citation statements)

References 14 publications

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“…We extracted aperture photometry for the detected sources using apphot in IRAF. Following Fischer et al (2013), for the 70 µm images we used an aperture radius of 9.6 arcsec, inner sky annulus radius of 9.6 arcsec and sky annulus width of 9.6 arcsec; for the 160 µm images we used an aperture radius of 12.8 arcsec, inner sky annulus radius of 12.8 arcsec and a 12.8 arcsec sky annulus width. The photometric error was determined as the sum in quadrature of the measurement error and the calibration error (see Briceño et al 2013).…”

Section: Pacs Observationsmentioning

confidence: 99%

A Herschel View of Protoplanetary Disks in the Σ Ori Cluster

Maucó

Hernández²,

Calvet

et al. 2016

ApJ

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We present new Herschel PACS observations of 32 T Tauri stars in the young (∼3 Myr) σ Ori cluster. Most of our objects are K & M stars with large excesses at 24 µm. We used irradiated accretion disk models of D' Alessio et al. (2006) to compare their spectral energy distributions with our observational data. We arrive at the following six conclusions. (i) The observed disks are consistent with irradiated accretion disks systems. (ii) Most of our objects (60%) can be explained by significant dust depletion from the upper disk layers. (iii) Similarly, 61% of our objects can be modeled with large disk sizes (R d ≥ 100 AU). (iv) The masses of our disks range between 0.03 to 39 M Jup , where 35% of our objects have disk masses lower than 1 Jupiter. Although these are lower limits, high mass (> 0.05 M ⊙ ) disks, which are present e.g, in Taurus, are missing. (v) By assuming a uniform distribution of objects around the brightest stars at the center of the cluster, we found that 80% of our disks are exposed to external FUV radiation of 300 ≤ G 0 ≤ 1000, which can be strong enough to photoevaporate the outer edges of the closer disks. (vi) Within 0.6 pc from σ Ori we found forbidden emission lines of [NII] in the spectrum of one of our large disk (SO662), but no emission in any of our small ones. This suggests that this object may be an example of a photoevaporating disk.

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Section: Pacs Observationsmentioning

confidence: 99%

A Herschel View of Protoplanetary Disks in the Σ Ori Cluster

Maucó

Hernández²,

Calvet

et al. 2016

ApJ

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“…The HOPS program was a far-IR survey of Spitzer identified protostars in the Orion molecular clouds. The HOPS team obtained and analyzed Herschel/PACS photometry of 330 protostars and PACS spectra of 36 protostars (Fischer et al 2010(Fischer et al , 2013Stanke et al 2010;Manoj et al 2013;Stutz et al 2013;Furlan et al 2016;Gonzalez-Garcia et al 2016). A detailed analysis of the far-IR spectra of the 21 brightest sources in the HOPS spectroscopy sample were presented in Manoj et al (2013).…”

Section: The Samplementioning

confidence: 99%

The Evolution of Far-Infrared Co Emission From Protostars

Manoj

Green

Megeath

et al. 2016

ApJ

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We investigate the evolution of far-IR CO emission from protostars observed with Herschel/PACS for 50 sources from the combined sample of HOPS and DIGIT Herschel key programs. From the uniformly sampled spectral energy distributions, whose peaks are well sampled, we computed the L bol , T bol ,and L L bol smm for these sources to search for correlations between far-IR CO emission and protostellar properties. We find a strong and tight correlation between far-IR CO luminosity (L CO fir ) and the bolometric luminosity (L bol ) of the protostars with µ L L CO fir bol 0.7 . We, however, do not find a strong correlation between L CO fir and protostellar evolutionary indicators, T bol and L L bol smm . FIRCO emission from protostars traces the currently shocked gas by jets/outflows, and far-IR CO luminosity, L CO fir , is proportional to the instantaneous mass-loss rate,Ṁ out . The correlation between L CO fir and L bol , then, is indicative of instantaneousṀ out tracking instantaneousṀ acc . The lack of acorrelation between L CO fir and evolutionary indicators T bol and L L bol smm suggests thatṀ out and, therefore,Ṁ acc do not show any clear evolutionary trend. These results are consistent with mass accretion/ejection in protostars being episodic. Taken together with the previous finding that the time-averaged mass-ejection/accretion rate declines during the protostellar phase, our results suggest that the instantaneous accretion/ejection rate of protostars is highly time variable and episodic, but the amplitude and/or frequency of this variability decreases with time such that the timeaveraged accretion/ejection rate declines with system age.

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“…Figure 6 shows the distribution of T bol and L smm /L bol for the protostars in the simulation, along with real observations. The observations are a conjunction of data from c2d (Evans et al 2009), the Spitzer Gould Belt survey (GB) (Dunham et al 2013), and the Herschel Orion protostar survey (HOPS) (Fischer et al 2013;Manoj et al 2013;Stutz et al 2013); also see Dunham et al (2014). The synthetic data in Fig.…”

Section: Classification Of Protostarsmentioning

confidence: 99%

Large-scale numerical simulations of star formation put to the test

Frimann

Jørgensen

Haugbølle

2016

A&A

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Context. Both observations and simulations of embedded protostars have progressed rapidly in recent years. Bringing them together is an important step in advancing our knowledge about the earliest phases of star formation. Aims. To compare synthetic continuum images and spectral energy distributions (SEDs), calculated from large-scale numerical simulations, to observational studies, thereby aiding in both the interpretation of the observations and in testing the fidelity of the simulations. Methods.The adaptive mesh refinement code, RAMSES, is used to simulate the evolution of a 5 pc × 5 pc × 5 pc molecular cloud. The simulation has a maximum resolution of 8 AU, resolving simultaneously the molecular cloud on parsec scales and individual protostellar systems on AU scales. The simulation is post-processed with the radiative transfer code RADMC-3D, which is used to create synthetic continuum images and SEDs of the protostellar systems. In this way, more than 13 000 unique radiative transfer models, of a variety of different protostellar systems, are produced. Results. Over the course of 0.76 Myr the simulation forms more than 500 protostars, primarily within two sub-clusters. The synthetic SEDs are used to calculate evolutionary tracers T bol and L smm /L bol . It is shown that, while the observed distributions of the tracers are well matched by the simulation, they generally do a poor job of tracking the protostellar ages. Disks form early in the simulation, with 40% of the Class 0 protostars being encircled by one. The flux emission from the simulated disks is found to be, on average, a factor ∼6 too low relative to real observations; an issue that can be traced back to numerical effects on the smallest scales in the simulation. The simulated distribution of protostellar luminosities spans more than three order of magnitudes, similar to the observed distribution. Cores and protostars are found to be closely associated with one another, with the distance distribution between them being in excellent agreement with observations. Conclusions. The analysis and statistical comparison of synthetic observations to real ones is established as a powerful tool in the interpretation of observational results. By using a large set of post-processed protostars, which make statistical comparisons to observational surveys possible, this approach goes beyond comparing single objects to isolated models of star-forming cores.

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Results from HOPS: A multiwavelength census of Orion protostars

Cited by 36 publications

References 14 publications

A Herschel View of Protoplanetary Disks in the Σ Ori Cluster

A Herschel View of Protoplanetary Disks in the Σ Ori Cluster

The Evolution of Far-Infrared Co Emission From Protostars

Large-scale numerical simulations of star formation put to the test

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