ISM Structures Traced byAKARI FIR All-Sky Dust Map

Yasuo Doi , T. Ootsubo , S. Takita , T. Nakagawa , M. Kawada , Y. Kitamura ,12S. Matsuura3 , M. Ha ori4 , M. Tanaka521222

U. of Tokyo, 2 ISAS, 3 Kwansei U., 4 Tohoku U., 5 Tsukuba U.

FIR dust map from AKARI data
90μm, 140μm → Tcol , τ ,radiance
β: ﬁxed or refer Planck data,etc.
Model SED ﬁt by DustEM, etc.

Other FIR dust maps
SFD : IRAS 5′ +TDIRBE′60

IRAS + Planck : 5′′′cf. AKARI: 1 ~2

M31 AKARI & Herschel images

Dust map evaluation: refer Planck data (resolution: 30′ )Intensity ratio between 90μm and 140μm →βTcol, I90μm → τ
Tcol , τ , β → radiance RTcol

R = ∫Iν dν = ∫
ν

= τνo

τν Bν (Tcol )(0νσsπT

4col(kTcolhν0βνβ)ν0Γ(4 + β)ζ(4 + β))Γ(4)ζ(4)Taurus dust map: PlanckTaurus dust map: AKARIAKARI vs. Planck E[B-V]Omnipresence of ISM ﬁlaments
One of the key ﬁndings of HerschelFilaments and star formation activities"universal" ∼ 0.1pc width of the ﬁlaments% prestellar cores found in ﬁlaments> 70

Mass Function of Dense Cores
Aquila CMF obs. by Herschel(Könyves et al. 2010; Andr é et al. 2010)

Filament formation – a 'missing link'in the star formation processes
From ∼ 100pc GMCs to < 0.1pc prestellar cores
A giant leap in the spatical scaleh p://www.astro.washington.edu/users/sjschmidt/A101/lectures.html

Necessity for the large spatial
dynamic range in the observations
From > 100pc GMCs to < 0.1pc prestellar cores
3> 10

diﬀerence in spatial scales

Obs. with high spatial resolution & spatially extendedemission – "spatial dynamic range"↓Advantage of the AKARI All-sky Survey

Filament extraction @ Taurus
Filament typical width: ∼ 0.1 pc ⇔ 2.5′ @ 140pc

Filament extraction @ Taurus
Filament typical width: ∼ 0.1 pc ⇔ 2.5′ @ 140pc

Filament extraction methods
DisPerSE (Sousbie, 2011, MNRAS, 414, 350)
Rolling Hough Transform (RHT; Clark et al. 2014 ApJ 789,82)
FilFinder (Koch et al. 2015, MNRAS, 452 (4), 3435)
These methods extract linearly elongated structure by
design -- omit detailed structure of ISM.

ISM structure identiﬁcation
density-based clustering method
estimate surface density of data
pointsﬁnd data points above a thresholdvalue
background noise can be eliminatedstructure of clusters is notpresupposed(image from Wikipedia)

ISM structure identiﬁcation in Taurus

ISM structure identiﬁcation in Taurus

ISM structure identiﬁcation in Taurus

ISM structure identiﬁcation in Taurus

ISM structure identiﬁcation in Taurus

ISM structure identiﬁcation in Taurus

Filaments formation and alignmentwith B-ﬁeld(Palmeirim+ 2013, A&A, 550, A38)

Filamets alignment with B-ﬁeld(Planck Collaboration+ 2016, A&A, 586, A138)

ISM structure vs. Planck B-ﬁeld

ISM structure vs. Planck B-ﬁeld>

ISM structure vs. Planck B-ﬁeld
AKARIPlanck(Planck Collaboration+ 2016, A&A, 586, A138)

Relative angle of θISM and θB
High-density ISM structure ⊥ B-ﬁeld
Low-density ISM structure ∥ B-ﬁeldBimodality is not as clear as seen byPlanck
Higher spatial resolution required for
B-ﬁeldWe need SPICA!

YSO distribution

YSO distance from adjacent ISM peaks

YSO distance from adjacent ISM peaks

YSOs vs. ISM concentrations"distance" correlates with age of thesources−1
60.1 pc = 0.1 km s
× 10 yrs
age-evolution of the YSO distributions(Doi+ 2015, PASJ, 67(3), 50)

Dust column at adjacent ISM peaks

YSOs vs. ISM concentrations"distance" correlates with age of the sources−1
60.1 pc = 0.1 km s
× 10 yrs
age-evolution of the YSO distributions(Doi+ 2015, PASJ, 67(3), 50)"density" correlates with age of the sources
age-evolution of ISM structures (ﬁlaments)
mass loss rate: < 10 M⊙ pc−1 Myr−1
cf. mass accretion rate: 27 − 50 M⊙ pc−1 Myr−1(Palmeirim+ 2013, A&A, 550, A38)
Statistical inference on age evolution of star-formation
environment "after" the formation of stars.

life cycle of ﬁlaments
1. mass accretion along B-ﬁeld (through striations)
2. exceeds critical mass → starts to form stars
3. termination of mass accretion
eating up surrounding material
strip oﬀ by SNe shocks
cf. Mdense cores/Mfilament ≤ 15% (eg. André +2014)
4. dissipation due to ISRF/radiation from internal YSOs
→ star-formation ends