TY - JOUR

T1 - The Spitzer c2d survey of large, nearby, interstellar clouds. X. the chamaeleon II pre-main-sequence population as observed with IRAC and MIPS

AU - Alcalá, Juan M.

AU - Spezzi, Loredana

AU - Chapman, Nicholas

AU - Evans, Neal J.

AU - Huard, Tracy L.

AU - Jørgensen, Jes K.

AU - Merín, Bruno

AU - Stapelfeldt, Karl R.

AU - Covino, Elvira

AU - Frasca, Antonio

AU - Gandolfi, Davide

AU - Oliveira, Isa

PY - 2008/3/20

Y1 - 2008/3/20

N2 - We discuss the results from the combined IRAC and MIPS c2d Spitzer Legacy survey observations and complementary optical and NIR data of the Chamaeleon II (Cha II) dark cloud. We perform a census of the young population in an area of ∼ 1.75 deg2 and study the spatial distribution and properties of the cloud members and candidate premain-sequence (PMS) objects and their circumstellar matter. Our census is complete down to the substellar regime (M ≈ 0.03 M⊙). From the analysis of the volume density of the PMS objects and candidates we find two groups of objects with volume densities higher than 25 M⊙ pc-3 and 5-10 members each. A multiplicity fraction of about 13% ± 3% is observed for objects with separations 0.8″ < θ < 6.0″ (142-1065 AU). No evidence for variability between the two epochs of the c2d IRAC data set, Δt ∼ 6 hr, is detected. We estimate a star formation efficiency of 1%-4%, consistent with the estimates for Taurus and Lupus, but lower than for Cha I. This mightmean that different star formation activities in the Chamaeleon clouds reflect a different history of star formation. We also find that Cha II is turning some 6-7 M⊙ into stars every Myr, which is low in comparison with the star formation rate in other c2d clouds. The disk fraction of 70%-80% that we estimate in Cha II is much higher than in other star-forming regions and indicates that the population in this cloud is dominated by objects with active accretion. Finally, the Cha II outflows are discussed; a new Herbig-Haro outflow, HH 939, driven by the classical T Tauri star Sz 50, has been discovered.

AB - We discuss the results from the combined IRAC and MIPS c2d Spitzer Legacy survey observations and complementary optical and NIR data of the Chamaeleon II (Cha II) dark cloud. We perform a census of the young population in an area of ∼ 1.75 deg2 and study the spatial distribution and properties of the cloud members and candidate premain-sequence (PMS) objects and their circumstellar matter. Our census is complete down to the substellar regime (M ≈ 0.03 M⊙). From the analysis of the volume density of the PMS objects and candidates we find two groups of objects with volume densities higher than 25 M⊙ pc-3 and 5-10 members each. A multiplicity fraction of about 13% ± 3% is observed for objects with separations 0.8″ < θ < 6.0″ (142-1065 AU). No evidence for variability between the two epochs of the c2d IRAC data set, Δt ∼ 6 hr, is detected. We estimate a star formation efficiency of 1%-4%, consistent with the estimates for Taurus and Lupus, but lower than for Cha I. This mightmean that different star formation activities in the Chamaeleon clouds reflect a different history of star formation. We also find that Cha II is turning some 6-7 M⊙ into stars every Myr, which is low in comparison with the star formation rate in other c2d clouds. The disk fraction of 70%-80% that we estimate in Cha II is much higher than in other star-forming regions and indicates that the population in this cloud is dominated by objects with active accretion. Finally, the Cha II outflows are discussed; a new Herbig-Haro outflow, HH 939, driven by the classical T Tauri star Sz 50, has been discovered.

KW - Circumstellar matter

KW - Infrared: stars

KW - Planetary systems: protoplanetary disks

KW - Stars: formation

KW - Stars: low-mass, brown dwarfs

KW - Stars: pre-main-sequence

UR - http://www.scopus.com/inward/record.url?scp=42149152595&partnerID=8YFLogxK

U2 - 10.1086/527315

DO - 10.1086/527315

M3 - Journal article

AN - SCOPUS:42149152595

VL - 676

SP - 427

EP - 463

JO - Astrophysical Journal

JF - Astrophysical Journal

SN - 0004-637X

IS - 1

ER -