A high-resolution survey of massive cores in Cygnus-X

Keping Qiu

Nanjing University

What is the SMA?

11 July 2011 SMA Community Day 4

The SMA is a pathfinding instrument comprised of eight 6 meter

antennas on Mauna Kea, HI, designed for high spatial and spectral

resolution imaging in submillimeter atmospheric windows.

The SMA is now being used to study Solar System bodies,

protoplanetary disks, star forming regions, evolved star envelopes, the

Galactic Center, nearby galaxies, and ultraluminous galaxies at

cosmological distances.

The SMA is a collaborative project of the Smithsonian Astrophysical Observatory, part of the Harvard-Smithsonian Center for

Astrophysics, and the Academia Sinica Institute of Astronomy and Astrophysics (Taiwan)

Outline

• Cygnus-X: background, sample of massive cores

• The SMA survey, and complementary data

• Preliminary results

• Summary and outlook

Why Cygnus X?

One of the richest molecular cloud and HII region complexes located at a distance <2kpc (~1.4 kpc, Rygl+2012);

The molecular cloud complex: mass ~ 106 M☉; size ~ 100 pc;

Already Mapped by various IR to mm telescopes (e.g., Spitzer, Herschel, JCMT, IRAM 30m).

ESA/

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2MASS extinction map (Motte+ 2007)

Why Cygnus X?

MAMBO 1.2mm survey: discovered 129 cores (~0.1pc); 42 massive (>30 M☉) (Motte+ 2007; also see followups by Schneider+ 2010; Bontemps+ 2010; Csengeri+ 2010; 2011; Duarte-Cabral+ 2013, 2014)

The SMA survey of massive CygX cores

What is the SMA?

11 July 2011 SMA Community Day 4

The SMA is a pathfinding instrument comprised of eight 6 meter

antennas on Mauna Kea, HI, designed for high spatial and spectral

resolution imaging in submillimeter atmospheric windows.

The SMA is now being used to study Solar System bodies,

protoplanetary disks, star forming regions, evolved star envelopes, the

Galactic Center, nearby galaxies, and ultraluminous galaxies at

cosmological distances.

The SMA is a collaborative project of the Smithsonian Astrophysical Observatory, part of the Harvard-Smithsonian Center for

Astrophysics, and the Academia Sinica Institute of Astronomy and Astrophysics (Taiwan)

A collaboration between Nanjing University (PI: Keping Qiu) and Smithsonian Astrophysical Observatory

1.3 mm, 2 × 6 GHz, continuum and various molecular spectral lines (e.g., CO, 13CO, C18O, SiO, H2CO, SO, CH3OH, CH3CN, …); !Subcompact + Compact + Extended, ~30 tracks for uv, resolution, sensitivity

Angular resolution ~1”, or <2000 AU, note thermal Jeans length ~ 10,000 AUContinuum sensitivity ≲1mJy, or <0.1 M☉, note thermal Jeans mass ~ 0.5 M☉

Complemented by JVLA (PI & archive), JCMT (PI & archive), Herschel (archive), Spitzer (archive), CARMA (PI, a small part of the sample)

Herschel 250µm

SCUBA2 850µm (credit to M. Thompson)

W75NDR21(OH)

AFGL2591IRDC G79.43

Cyg OB2

100 pc

The SMA survey of massive CygX cores

Preliminary results

~2/3 of the sample, 28 massive cores + 12 lower mass cores in the FoV fragmentation seen in almost all the cores; ~1/2 have fragments nearly linearly distributed (~0.1pc) !singly peaked (down to 0.01pc) sources, though very rare, also seen (why, is fragmentation suppressed? how?) !starless sources appear to be detected, and also fragment (why no SF, not yet or would never happen?)

Preliminary results

fragmentation level as a function of core mass, and column density?

The fragmentation (0.1 ➙ 0.01pc) does not correlate with the mass or column density; neither it is correlated with the evolutionary stage.

On the scales of relevance (<0.1 pc), gravity is apparently dominating over magnetic fields and turbulence, but the fragmentation does not seem to be a simple/complete “gravitational” process.

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mass of the cores (M☉) column density of the cores (M☉ pc-2)

Preliminary resultsany fragmentation pattern as seen from the separations?

1st NNS

Jeans lengths @10K, 105cm-3! @20K, 106cm-3

Jeans lengths @10K, 105cm-3! @20K, 106cm-3

Jeans lengths @10K, 105cm-3! @20K, 106cm-3

Jeans lengths @10K, 105cm-3! @20K, 106cm-3

1st NNS

3rd NNS 4th NNS

2nd NNS

Summary and outlook

• The project is to map 40+ massive cores in the continuum and spectral lines @1.3mm, with a continuum sensitivity of 1 mJy (~0.1 Msun) and an angular resolution of ~1’’ (~1400 AU); so far ~2/3 of the sample done.

• Most cores fragment into a group of condensations; preliminary analyses show that 1) the process doesn’t seem to be fully controlled by gravitational physics; 2) the fragmentation proceeds down to the resolution limit (~1500AU), without a clear preference. The physics/mechanisms underneath unclear.

• Completing the SMA survey and complementary observations (both PI and archival)

• Full analysis of the entire sample: fragments (numbers, separations, masses, velocity dispersions, evolutionary stages, …); star formation activities (infall/accretion, jets and outflows, environmental effects, triggering mechanisms, …).