Line Survey of Low-Mass Star Forming Regions Satoshi Yamamoto, Nami - - PowerPoint PPT Presentation

Line Survey of Low-Mass Star Forming Regions

Satoshi Yamamoto, Nami Sakai, Takeshi Sakai, Shuro Takano, and NRO 45m Line Survey Group

Outline of this talk

(1) Introduction (2) Chemistry of Class 0 sources (3) Line Survey with ALMA

Star Formation and Astrochemistry

Chemical Evolution to Planets Chemical Diagnostics of Star and Planet Formation

Interstellar Molecules

• H2
• CO
• HCN, HNC, H2CO, NH3, CS, SiO, CN, SO, SO2
• H3+, HCO+, HN2+, HCS+, C6H-
• HC3N, HC5N, HC7N, HC9N, HC11N
• C2H, C3H, C4H, C5H, C6H, C8H, CCS, C3S
• CH3OH, HCOOCH3, (CH3)2O, C2H5CN,

CH3CHO, HCOOH, C2H5OH, ～150 Species

Carbon Chains

HN2

+, NH3

Deuterated Species DCO+, H2D+ Complex Organic Molecules

C → CO Conversion CO Depletion Mantle Evaporation

Chemical Evolution of Molecular Clouds

＋ Caselli et al. 2002 Ohashi et al. 1999

Formation of Complex Organic Molecules

CH3OH H2CO Gas phase reaction HCOOCH3 CH3OCH3

Hot Phase

CO CO H H CO H H CH3OH H2CO CO H

Cold Phase

Grain surface reaction Caselli et al. 1999 L1544

Cazaux et al. ApJ 593, L51 (2003) C2H5CN HCOOCH3

• NGC1333 IRAS 4B

(Dynamical Time Scale of Molecular Outflow) Choi, M. 2001, ApJ, 553, 219) rms ; 3.6 mK

Center Frequency ；89.3146 GHz HCOOCH3 E

• N. Sakai et al. PASJ 58, L15 (2006）

Detection of HCOOCH3

VLSR ; A 7.1 km/s TMB ; A 22 mK ΔV ; A 1.2 km/s

• Distance ； 220 pc (Perseus)
• Mass ； about 0.4 M⊙
• Class 0 (a few 100 yr)

0.4 M⊙ Class 0

On-source Integration Time :18.5 h

Carbon Chains

HN2

+, NH3

Deuterated Species DCO+, H2D+ Complex Organic Molecules

C → CO Conversion

Chemical Evolution of Molecular Clouds

CO Depletion Mantle Evaporation

L1527

Luminosity : 2 L⊙ Distance : ～140 pc (Taurus) Class 0 – Class I

（NRO 45 m, 2005/12-2006/01 ） ν0 ；89.3146 GHz, HCOOCH3 E

Complex species were not detected The on-source integration time : 22 h

rms : 2.1 mK

Luminosity : 6 L⊙ Distance : ～220 pc cf : NGC1333 IRAS 4B TA* = 11 mK (Obs.) Predicted TA* = 9.2 mK

Various Carbon-Chain Molecules in L1527

★ CH3CCH ★ l-C4H ★ c-C3H2 (N = 9 – 8, Eu = 21 K) (43, 2 – 42, 3, Eu = 29 K) (J=5 – 4,K = 2, Eu = 41 K) ★ l-C3H2 (41, 3 – 31, 2, Eu = 23 K)

High Excitation Lines !

★ l-C5H, l-C6H, l-C6H2, HC7N, HC9N

@ 18-20 GHz (GBT, 2006, Dec.)

Long Carbon-Chains !

@ 80-90 GHz (45 m Telescope, 2007, Feb.-Mar.) ★ C6H-, C4H-

Negative Ions !

@ 85-106 GHz, IRAM 30 m Carbon-chain molecules exist in warm and dense part

• f the star forming region !! (N. Sakai et al. 2008)

★ HC5N (J = 32 – 31, Eu = 67 K, J = 33－32, Eu = 71 K, J = 40－39, Eu = 104 K) preliminary

Detection of Very High Excitation Lines

Very High Excitation Lines !

(Trot ~ 26±12 K)

Fast collapse (close to free fall case)

～105 yr Star-formation ～106 yr

cf NGC1333IRAS4B IRAS16293－2422 Carbon-chain molecules are deficient. Starless core ①Some carbon-chain molecules could survive even after onset of star formation L1527

CH4 + C+ → C2H3

+ + H

C2H3

+ + e →C2H + H + H → ･･･

②Carbon-chains are regenerated by evaporation of methane(CH4)

(Sakai et al. 2008; Aikawa et al. 2008).

Warm Carbon-Chain Chemistry (WCCC)

Origin of Rich Carbon-Chains in L1527

C4H Survey with NRO 45 m

Search for the Second WCCC Source

30’ A B Tachihara et al. 1996

IRAS15398-3359 in Lupus 1

Hara et al. 1999

IRAS15398-3359 in Lupus

★Various carbon- chains are abundant !

HC5N (J=32-31, Eu=67 K)

HCO2

+ (404-303)

★Strong high excitation lines !

Chemical Variation of Low-Mass SFRs

ex; IRAS16293–2422 NGC1333 IRAS4A/4B ★ ★

C4H2 (101, 9－91, 8)

Hot corino chemistry Warm carbon-chain chemistry Carbon-chains are deficient ! L1527, IRAS15398-3359 Abundant Carbon-chains ! Difference in physical processes

• f star formation

CO CO CO CO CO CO H H H H H CH3OH CH3OH CH3OH CO CH3OH C C C C CO H C H H H H CH4 CH4 CH4 depleted as C

Fast collapse （~ free fall timescale） Abundant Carbon-Chains (ex. L1527 and IRAS15398-3359) C

depleted as CO

Slow collapse Abundant COMs (HCOOCH3, (CH3)2O, etc.) CH4 C C

Scenario

(ex. IRAS16293-2422 and NGC1333IRAS4A/4B)

How is chemical evolution after the Class 0 stage?

Key: Minor species!!

Major species does not show any variation ! Sensitive line survey is necessary !!

Line Survey of Protostellar Disks with ALMA

• Purpose

(1) Exploring chemical evolution from protostellar disks to protoplanetary disks (2) Providing new observation tools to study star and planet formation

• Targets

Class 0, Class I and Class II sources 10 Objects in total.

Class 0 Class I Class II

(1) Resolve an envelope and a disk (2) Study chemical evolution of an envelope and a disk (3) Study chemical interaction between an envelope and a disk (4) Explore possible source-to-source variation of chemical evolution

Envelope Disk

Line Survey with Interferometer:

Powerful Tool for Chemical Analysis

Kuan et al. (2004) Molecules in IRAS16293-2422 with SMA

Target Sources (1)

• Class 0 Sources

Hot Corino Sources IRAS16293-2422 WCCC Sources IRAS15398-3359, L1527 Intermediate Sources L483, B1, IRAS13036-7644 Line Survey with NRO 45 m (ALMA sub-working group activity) L1527 ( L1157) Many Unexpected Lines Some Unidentified Lines

Target Sources (2)

• Class I and Class II Sources

Need to search for candidate sources by observing minor molecules with existing telescopes (NRO 45 m, ASTE, etc) prior to ALMA observations! Possible chemical variation? (c.f. Hot Corino and WCCC) A few sources in each class will be surveyed. (Survey will start from Class 0 sources…)

Observing Frequencies

B: rotational constant ν： transition frequency Eu: upper state energy ν=2B(J+1) ～ 2BJ Eu=BJ(J+1) ～ BJ2 ～ ν(ν/4B) Molecular size B/GHz Eu/K (@300 GHz) Eu/K (@100 GHz) C2 40 30 4 C3 10 105 13 C4 5 210 25 C5 3 350 42 C6 1.5 750 83 Importance of Band 3, 4, and 6. Supplementary use of Band 7

Detection of Larger Species Is Equivalent to Detection of High Excitation Lines!

Observing Strategy

• Frequency Range --- Full Survey!

Band 3 84-116 GHz 0.8 GHz x 40 settings Band 4 125-169 GHz 1.2 GHz x 36 settings Band 6 211-275 GHz 1.8 GHz x 36 settings Band 7 275-373 GHz 2.8 GHz x 35 settings Total 147 settings

• Assumptions

Velocity resolution 0.3 km/s Backend 8192 channels

ALMA Sensitivity

• Sensitivity calculation with ETC
• Freq. Main Array 7m Array TP

100 GHz 808 mK 24 mK 7 mK 150 GHz 382 mK 26 mK 7 mK 230 GHz 215 mK 33 mK 9 mK 350 GHz 154 mK 54 mK 14 mK

• Assumptions

Spatial resolution 1” Velocity resolution 0.3 km/s Integration time 600 s = 10 min

Time Estimate

• Use Main Array with ACA and TP

147 settings x 10 min = 1470 min 10 sources x 1470 min = 14700 min 4 Class 0 sources 3 Class I sources 3 Class II sources Overheads 20% 18000 min (300 hrs) ACA and TP are necessary to recover extended components!!

Line Survey of TMC-1 with NRO 45 m

Kaifu et al. (2004) HC3N HC5N HC7N CCS, CCCS, c-C3H, CCO, CCCO, C4H2, etc

Carbon-Chain Chemistry ↓ Concept of Chemical Evolution

Collaborators

• Dr. Nami Sakai (Univ. of Tokyo)
• Mika Sugimura (Univ. of Tokyo)
• Osamu Saruwatari (Univ. of Tokyo)
• Dr. Takeshi Sakai (NAOJ)
• Dr. Tomoya Hirota (NAOJ)
• Dr. Shuro Takano (NAOJ)
• NRO 45 m Line Survey Group Members

2nd Tokyo-NRO Workshop

Chemical Diagnostics of Star Formation

March 5 and 6, 2009 Hongo-Campus, The University of Tokyo

Overseas Invited Speakers: Jes Jorgensen (U. Bonn) Suzanne Bisshop (MPI, Bonn) Henrik Beuther (MPI, Heidelberg) Yancy Shirley (U. Arizona) Sheng-Yuan Liu (ASIAA)