PROPERTIES OF THE YOUNGEST PROTOSTARS IN PERSEUS, SERPENS, AND OPHIUCHUS

By M. Enoch, N. Evans II, A. Sargent, J. Glenn. 2008

284 citations recorded by the source corpus.

We present an unbiased census of deeply embedded protostars in Perseus, Serpens, and Ophiuchus, assembled by combining large-scale 1.1 mm Bolocam continuum and Spitzer Legacy surveys. We identify protostellar candidates based on their mid-infrared (mid-IR) properties, correlate their positions with 1.1 mm core positions from Enoch et al. in and , and Young et al. in , and construct well-sampled spectral energy distributions using our extensive wavelength coverage (λ = 1.25–1100 μm). Source classification based on the bolometric temperature yields a total of 39 Class 0 and 89 Class I sources in the three-cloud sample. We compare to protostellar evolutionary models using the bolometric temperature–luminosity diagram, finding a population of low-luminosity Class I sources that are inconsistent with constant or monotonically decreasing mass accretion rates. This result argues strongly for episodic accretion during the Class I phase, with more than 50% of sources in a “sub-Shu” (dM/dt < 10−6M☉ yr−1) accretion state. Average spectra are compared to protostellar radiative transfer models, which match the observed spectra fairly well in Stage 0, but predict too much near-IR and too little mid-IR flux in Stage I. Finally, the relative number of Class 0 and Class I sources is used to estimate the lifetime of the Class 0 phase; the three-cloud average yields a Class 0 lifetime of 1.7 ± 0.3 × 105 yr, ruling out an extremely rapid early accretion phase. Correcting photometry for extinction results in a somewhat shorter lifetime (1.1 × 105 yr). In Ophiuchus, however, we find very few Class 0 sources (NClass 0/NClass I ∼ 0.1–0.2), similar to previous studies of that cloud. The observations suggest a consistent picture of nearly constant average accretion rate through the entire embedded phase, with accretion becoming episodic by at least the Class I stage, and possibly earlier.

Subfields: Astronomy and Astrophysics, Spectroscopy

View Paper: https://www.semanticscholar.org/paper/0932e291be1b0f4692b5f8c5c70c134470db834e

How researchers see this paper

The researchers whose trusted networks rank it highest, strongest advocate first. Every researcher gets a different order.

In Astronomy and Astrophysics

1. N. Evans II
2. Ralf Klessen
3. Mark R. Krumholz
4. K. Luhman
5. P. Myers
6. G. Herczeg
7. L. Hillenbrand
8. L. Hartmann

In Spectroscopy

1. N. Evans II
2. Simon Bruderer
3. E. Bergin
4. P. Caselli
5. K. Luhman
6. G. Herczeg
7. M. Tafalla
8. E. Dishoeck

Citations in the corpus

• Star Formation in the Milky Way and Nearby Galaxies (2012, background): “In nearby clouds, these correspond to dense cores (Enoch et al. 2009).”
• EPISODIC ACCRETION AT EARLY STAGES OF EVOLUTION OF LOW-MASS STARS AND BROWN DWARFS: A SOLUTION FOR THE OBSERVED LUMINOSITY SPREAD IN H–R DIAGRAMS? (2009, background): “…consistent explanation for current observations of protostars, while a short (∼ 104 yr) accretion phase based on previous estimates of class 0 lifetimes, with accretion rates significantly decreasing during the subsequent class I phase, seems to be ruled out (Enoch et al. 2009; Evans et al. 2009).”
• THE HERSCHEL ORION PROTOSTAR SURVEY: SPECTRAL ENERGY DISTRIBUTIONS AND FITS USING A GRID OF PROTOSTELLAR MODELS (2016, background): “Young, deeply embedded protostars have spectral energy distributions (SEDs) with steeply rising slopes in the infrared, peaking around 100 µm, and large fractional submillimeter luminosities (e.g., Enoch et al. 2009; Stutz et al. 2013).”
• STAR FORMATION RELATIONS IN NEARBY MOLECULAR CLOUDS (2014, background): “They are also targeted in Herschel surveys covering 60 to 500 µm (André et al. 2011), and some have been studied in more detail in millimeter continuum emission (e.g., Enoch et al. 2009) and molecular lines (e.g., Ridge et al. 2006).”
• THREE-DIMENSIONAL SIMULATION OF MASSIVE STAR FORMATION IN THE DISK ACCRETION SCENARIO (2011, background): “Observations with reference to low-mass star formation clearly favor the episodic accretion events shown in our three-dimensional simulation, see e.g. Enoch et al. (2009); van Boekel et al. (2010) for most recent examples.”
• MAPPING THE SHORES OF THE BROWN DWARF DESERT. II. MULTIPLE STAR FORMATION IN TAURUS–AURIGA (2011, background): “Observations suggest that the characteristic radius for a protostellar disk and for accretion onto it is 50– 100 AU (Enoch et al. 2009; Watson et al. 2007), so disk fragmentation could explain binary formation at small scales where prompt fragmentation is not feasible.”
• RESOLVING THE LUMINOSITY PROBLEM IN LOW-MASS STAR FORMATION (2011, background): “Core masses for all objects in Perseus, Ophiuchus, and Serpens are taken from Enoch et al. (2009a).”
• Water in star-forming regions with Herschel (WISH). II. Evolution of 557 GHz 110-101 emission in low-mass protostars (2012, methodology): “The mass estimates presented here fall well within the range of masses derived for these sources using other methods (Bontemps et al. 1996; Hogerheijde et al. 1997, 1998; Chen et al. 2008; Enoch et al. 2009; Jørgensen et al. 2009).”
• THE BURST MODE OF ACCRETION AND DISK FRAGMENTATION IN THE EARLY EMBEDDED STAGES OF STAR FORMATION (2010, background): “…with α > 0.01 was also found in the context of barotropic disks (Vorobyov & Basu 2009a; Vorobyov 2009b) and this confronts recent observations of Enoch et al. (2009), who find that a considerable fraction of Class I sources in young star-forming regions have inferred accretion rates below…”
• YOUNG STELLAR OBJECTS IN THE GOULD BELT (2015, result): “Thus, we find that approximately one third (65/[65 + 129] = 0.335) of protostars are classified as Class 0, in agreement with previous results based on the smaller c2d-only sample (Enoch et al. 2009; Evans et al. 2009).”
• Effect of episodic accretion on the structure and the lithium depletion of low-mass stars and planet-hosting stars (2010, background): “There is a growing consensus in the star formation community that non steady (episodic) accretion plays a dominant role during the formation of low-mass stars (see e.g Enoch et al. 2009; Vorobyov 2009; Zhu et al. 2010a and references therein).”
• THE ROLE OF MULTIPLICITY IN DISK EVOLUTION AND PLANET FORMATION (2011, background): “Disks initially form early in the Class 0/I protostellar stages (Shu et al. 1987; Enoch et al. 2009), acting as the conduits through which massive circumstellar envelopes are 1 Hubble Fellow; Institute for Astronomy, University of Hawaii, 2680 Woodlawn Dr., Honolulu, HI 96822, USA 2 Sydney…”
• THE VLA NASCENT DISK AND MULTIPLICITY SURVEY OF PERSEUS PROTOSTARS (VANDAM). II. MULTIPLICITY OF PROTOSTARS IN THE PERSEUS MOLECULAR CLOUD (2016, methodology): “Per-emb-42 may be more evolved than L1448C, given that it is classified as a Class I by Enoch et al. (2009).”
• Gravitational Instabilities in Circumstellar Disks (2016, background): “There are several other tentative detections of Class 0 disks (see e.g. Looney et al. 2000; Enoch et al. 2009).”