Searching the First Hydrostatic Coresin the Perseus Molecular Cloud
Hao-Yuan Duan 段皓元 & Shih-Ping Lai 賴詩萍
National Tsing-Hua University, Taiwan

First collapse
Compressional heating
Radiative cooling
T~200K

Isothermal collapse (10K)First Core Here!
a quasi-adiabatic hydrostatic object
mostly H2shock form at the surface
Second collapse
Release gravitational energy
consumed by H2 dissociation
Second core / Class 0 protostar
mostly H atom

First Hydrostatic Core (FHC)Ø The transient phase between prestellar cores and Class 0 protostars.
Ø Short lifetime (103 – 104 yr, Boss & Yorke 1995).
Ø No near infrared continuum.
Ø Slow outflows (a few km/s).
Ø Can be heated over ∼100K in a very short period ∼ 5000 yr.
due to the accretion shocks (Masunaga & Inutsuka 2000).
Ø Size about ~AUØ Extremely difficult to be detected directly.
Ø It is a key to understand the earliest stage of star formation.

The aim of this project
Ø Several FHCs candidates were suggested ( < 10 ), but none of them
have been confirmed.
Ø In this work, we produce synthesis images using CASA simulation
based on a simple density profile model. We match the simulated
images to the First Core candidates B1-bN with SMA, ALMA and VLA
observational results.
Ø Our simulations show that with ALMA observations, we can decouple
the FHC component from envelope.
Ø The identification of FHCs will make great strides in our understandingof star formation.

First Core candidates
Ø Chamaeleon-MMS1 (Belloche et al. 2006) (Tsitali et al. 2013)(Väisälä et al. 2014)
Ø L1448 IRS2E (Chen et al. 2010)
Ø Per-bolo 58 (Enoch et al. 2010) (Dunham et al. 2011)
Ø L1451-mm (Pineda et al. 2011) (Maureira et al. 2017)
Ø Per-Bolo 45 (Schnee et al. 2012)
Ø CB 17 (Chen et al. 2012) (Schmalzl et al. 2014)
Ø B1-bS and B1-bN (Pezzuto et al. 2012) (Huang & Hirano 2013)(Hirano & Liu. 2014) (Gerin et al. 2015)Ø IC 348-SMM2E (Palau et al. 2014)

First Core candidates in the Perseus Molecular CloudB1-bN & B1-bS

JØøRGENSEN ET AL. 2006 SPITZER c2d SURVEY. III.

B1-bN & B1-bS

JØøRGENSEN ET AL. 2006 SPITZER c2d SURVEY. III.

Hirano & Liu. 2014
850 μm (dot contours) and 3.3 mm(solid contours) continuum maps of theB1-b region on top of the Spitzer MIPS
24 μm image (gray scale).

B1-bN & B1-bS

JØøRGENSEN ET AL. 2006 SPITZER c2d SURVEY. III.

Hirano & Liu. 2014
850 μm (dot contours) and 3.3 mm(solid contours) continuum maps of theB1-b region on top of the Spitzer MIPS
24 μm image (gray scale).

VLA:
Tobin et al. 2016 VANDAM
ALMA band7:
Gerin et al projectcode: 2015.1.00025.S

B1-bN & B1-bS

Synthesis images from interferometer:
Resolve out the envelope and Resolve the First Core directly?

JØøRGENSEN ET AL. 2006 SPITZER c2d SURVEY. III.

Hirano & Liu. 2014
850 μm (dot contours) and 3.3 mm(solid contours) continuum maps of theB1-b region on top of the Spitzer MIPS
24 μm image (gray scale).

VLA:
Tobin et al. 2016 VANDAM
ALMA band7:
Gerin et al projectcode: 2015.1.00025.S

SEDs of First Hydrostatic Core

T=10K
M=0.029 M◉

T=10.8K
M=0.037 M◉

T=12.4K
M=0.032 M◉

T=10K
M=0.074 M◉
T=12.9K
M=0.021 M◉

The radiation of short wavelength
emitted by the FHCs are essentiallycompletely reprocessed by the dusts
which surround the FHCs in the parent
envelopes to longer wavelength.
・Interferometer・ ・ Single dish

SED of B1-bN (Envelope + Compact core?)

ALMASMA
NMA

VLA

T=10.8K
M=0.037 M◉

SED of B1-bN (Envelope + Compact core?)

Compact component?

ALMASMA
NMA

VLA

T=10.8K
M=0.037 M◉

Build a First Core modelØThe idea is to build a First Core model (Envelope + Compact component).
ØUsing B1-bN as a standard.
Ø The envelope is constrained by single dish observations.
ØThe compact component can be resolved by the interferometry.
ØWe run CASA “simobserve” task to produce synthesis images of our model.
ØCompare our model to B1-bN.

Build a First Core model
𝐼5 (𝑠) = 𝐼5 𝑠7 𝑒Log ⍴9:; )< ,)A)+ ∫) 𝑗. (𝑠′)𝑒 9:; ) ,) 𝑑𝑠′<CASA “simobserve” tasks⍴c = 10-15 g/cc

(Inutsuka, S. PTEP 2012, 01A307 )slope: S (=-2)
T=10.8K
M=0.037 M◉~AU first core?

~700AUlog R_env

Estimate Menv, dust and Tdust from SED.
𝐹. 𝐷 0𝑀(#$%,'()*) =𝜅. 𝐵. (𝑇'()* )Pezzuto et al. 2012
Compare the synthesised images
to real observations

Compare the model images to real observations

Realobservations

synthesised imagesof models

SMA 1.1mm Hirano & Liu. 2014

ALMA band7: Gerin et al
project code: 2015.1.00025.S

Tobin et al. 2016 VANDAM

ALMA band7

VLA 8mm

Annular analysis

0.4” beam size

3𝜎
ALMA band7

Testing different parameters of our modelLog ⍴⍴c = ~10-13 g/cc

T=10.8K
M=0.037 M◉

0.4” beam size

S=-2
S=-3~700AU
S=-3.2

S=-2
S=-3.2

S=-33𝜎log R_env

Testing different parameters of our model
Log ⍴⍴c = ~10-13 g/cc

T=10.8K
M=0.037 M◉

0.4” beam size

~700AU
S=-3.2

S=-3.23𝜎log R_env

Preliminary result
500K⍴c = ~10-7 g/cc
0.001M◉Log ⍴0.4” beam size

T=10.8K
M=0.037 M◉~700AU
S=-3.2

S=-3.2
3𝜎

10AU

log R_env

SummaryØWe produce FHC synthesis images using CASA ‘simobserve’ based on asimple model.
ØThe aim is to see whether the First Core can be resolve by theinterferometry or not.
ØWe mimic the the simulated image of B1-bN to match the observational
results from :ü Hirano & Liu (2014), which present SMA 1.1mm continuum images,
ü Tobin et al. (2016), which present VLA 8mm continuum images,
ü ALMA band 7 continuum images(Gerin et al. 2015).

ØWe test different density profiles of our model, the slope of the density
profile of envelope may be ~⍴ ∝ r -3.2
ØA hot compact object must be added at the center (FHC?).
ØThis model may be use to identify First Hydrostatic Cores!