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Molecular cloud and star formation. Yuefang Wu Star formation group Astronomy Department Peking University. Outline Progress obtained in the past: 1. Gas heating and motion in molecular clouds:

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molecular cloud and star formation
Molecular cloud and star formation

Yuefang Wu

Star formation group

Astronomy Department

Peking University

slide2
Outline
  • Progress obtained in the past:
  • 1. Gas heating and motion in molecular clouds:

(1). Energetic of Molecular clouds—remain problem

(2). Motions and distribution of molecular species

2. Core and their property

3. High velocity molecular outflows

4. Collapse of star formation region

5. Triggering of star formation

  • This year: New subject: ISM and initial states of star forming
  • Future Work:

Confidence for the Millimeter Astronomy of our country

Planck cores of all the sky

  • Massive star formation
progress obtained
Progress obtained
  • Beginning

Thanks are given to Prof. Shou-Guan Wang introduced to us

“Astrophysics of interstellar molecules” by

Prof. G. Winnewisser of Cologne Univ. 1n 1979

  • Owing to: Efforts of teachers and students

Collaborating with domestic and abroad colleagues

Progresses were obtained during the past ~30 years:

1. Molecular clouds:

(1). Energetic of Molecular clouds—remain problem

Energetic of molecular cloud-last 70’

Problem remained:

8 clouds were not agreed wit the standard picture

Our work demonstrated: dust=gas couple well

except 1-2 persist: possible reasons

Wu & Evans, 1989; Wu et al. 1990

slide4
(2). Motions and distribution of molecular species

Nearby dark cores

thermal motion dominates them according to previously NH3 studies

We test it with emission of more heaver molecular specie CS

Result I: Line widths of heavier molecule > those of light ones

Result II. Emission regions of heavier molecule > those of light ones

---two puzzles

 Non–thermal dynamical processes dominate these cores

There is chemical differentiation

Onion model of molecular cloud is ideal situation

Zhou, Wu et al. 1989; Wu 1992

slide5
2. Core and their property
  • Surveys for cores:

UC HII candidates IRAS colour indexes 1-0 of CO 13CO C18O

Extremely young stellar objects: Own indexes CO2-1, 3-2

Water masers with weak IRAS NH3 (1,1) (2,2) (3,3) (4,4)

Massive cores: guided by Methanol masers 1-0 of CO 13CO C18O

 350 regions were searched

180 cores with different evolutional phases were obtained

  • Anatomy of cores:

example: G28.34+0.06:

slide6

Wu et al. 2001

Wang, Wu et al. 2009

Liu, Wu, Ju 2010

Ren, Wu, Liu et al. 2012

slide7
- Physical properties: Dynamical processes; Evolutional states

We also made detailed investigation for typical cores:

Wu et al. 2006

Wang et al. 207

slide8
Hierarchical fragmentation
  • High collimated bipolar outflows exist in high mass star forming regions too

Wang et al. 2012

Wang et al. 2007

slide9
3. High velocity molecular outflows:
  • Molecular outflows searched and identified:

Both single dishes, interferometers used

  • Water maser: searched; time variation
  • HH object driving sources identified: new method
  • Up-dated study was made for 25 years1

 • Inclination Angle -- derived from observation

• Common of in high mass star formation too 39% of 391 are high mass ones

• Demonstrate the indirect correlation

Lbol ------- mass accretion rates ---------

outflow mass -------- mass loss rate -----

• Demonstrate non-radiation stellar driving.

slide12

logM=-1.04 +/- 0.08+(0.56 +/- 0.02)logLbol

r = 0.78

R=0.73

Wu et al. 2005

Wu et al. 2004

slide14
4. Collapse of high mass star formation regions:
  • The question for high mass star formation:

Radiation halts the mass for Msun>8 YSOs

Seek and search for collapse signatures:

Obtained three results for which no similar report was seen before:

(1). Mapped Core JCMT 18354-0649S:

We found this core at Effelsberg 100 m, followed up

study with JCMT, the referee point out

it was a leading sample and suggested its name

- 4 evidences for collapse

the strongest signature is at the center

associated with outflow

Wu, Zhu, Wei et al. 2005

slide15
We also studied this core with SMA:
  • Follow up studies were also done by
  • Zhu et al. 2011

Liu et al

2011

slide16
Carolan et al. (2009) made

more line observations and 3D modell

analyse, quoted our results 9 times

and used the data that we observed

slide17
(2) Carried a mapping survey: Using IRAM
  • two groups of different evolutional samples were surveyed with

multiple lines:

I: UCHII precursors II: UCHII regions

  • Blue excess: E group II > E of group I:

Wu et al. 2007

slide18
Inflow motion in different evolutional phases:

Sources Evolutionary phases

-----------------------------------------------------------------------------------------------------

High mass Earlier than PUCHII PUCHII UC HII

examples ISOSS, Core JCMT G34.26 (total >70) E HCO+(1-0) …… 17% 58% (this work)

15%a 53% (CO 4-3)b

HCO+(3-2) -0.04e

----------------------------------------------------------------------------------------------------

slide19
W3-SE– PUCHII

G23.44-0.18- PUCHII

CARMA

CARMA+IRAM

Zhu et al.. 2010

Ren et al. 2011

slide20

G9.62+0.19, SMA

Core F PUCHII

Core E UCHII

Liu et al. 2011

slide21
Evolution time tendency-seems consistent with single dish results

HMC HMPSOs UC HII Regions

G9.62+0.19-F Core JCMT, W3-SE G19.6, N7538

Single dish Red profile blue profile blue profile

interfero. Red deeper pro. blue deeper pro. inverse P Cygni profile

• The results seem to be consistent with the statistical increase

of red profiles, or less “blue excess ” in HMPOs than

in UC HII regions

slide22
New method of identification

for collapse signature

two lines 

one line with map

Wu et al. 2007

slide23
(3). G19.61-0.23

Inside-out evidence

was obtained

for the first time:

R(CO) > R (CN)

Vin(CN)> Vin (CO)

inside out collapse

by Shu et al. (1987)

Wu et al. 2009

slide24

5. Triiggering of star formation

  • S87—Cloud collision

Collision and trigged cores

First time using HCO+ lines measured at PMO 13.7 m

Xue & Wu 2008

  • W75N and DR21—Cloud collision

Velocity structure, and star formation activities

Mao, Wu, Liu 2009

  • WR –HD211853: wind triggering

Wind triggering (Liu, Wu, Zhang, Qin 2012)

slide27

WR

HD211853

slide28
More recently, Planck early results were studied:
  • C3PO: Cold Core Catalogue of Planck Objects: 10783 clumps
  • ECC: the early Cold Core Catalogue : 915, most relable
  • We surveyed 674 ECC cores using 13.7 m telescope of PMO

with J=1-0 lines of CO, 13CO and C18O (Wu, Liu, Meng, Li, Qin 2012)

  • Revealed gas properties: For example:
  • Cold: Tex: 4—37 K quiet:
slide30
Their

Emission

regions

and

mophologies

slide31
Mapping study was also made for Complex
  • Orion (Liu, Wu, Zhang 2012) & Taurus (Meng, Wu, Liu 2012)
slide32
Evolutional states:

Among the 6 samples

shown in the figure,

4 were our group’s.

future work
Future Work
  • Confidence for the Millimeter Astronomy of our country

--the foundation and condition that is already present

• Science base, frontier subject

• Team of talents prepared

Continue to collaborate

• Our own new equipment

International advanced equipment

slide34

PMO 13.7 m

NRAO 12 m

Shanghai 25 m Xinjiang 25 m

Effelsberg 100 m KOSMA 3 m

slide35

Upper:

IRAM JCMT CSO

Lower:

GBT MOPRA

slide36

SMA

VLA/EVLA

slide37
Planck cores of all the sky:

CO results show: 4 kinds of states:

diffuse-YSOs  core-YSOs Core+YSOs dissuse+YSOs

• Initial conditions;

• IMF

• cloud formation

• cloud evolution

  • Massive star formation:

• Disk -- beginning from all

the intermediate mass stars

• collapse – evolution with time

• Stimulating formation: feed back (burst, HII, WR)