Small Loose Young Associations

The SACY Project

Search for Associations

Containing Young stars

Carlos A. O. Torres & Germano R. Quast (LNA / MCT/BRAZIL)

Claudio H. F. Melo & Michael Sterzik (ESO)

Ramiro de la Reza & Licio da Silva (ON / MCT/BRAZIL)

80’s - Isolated T Tauri stars?

89 - New T Tauri stars found around TW Hya

90’s - PDS (IRAS)

2000 - Horologium Association (ROSAT) & Tucana Association

Both nearby (~50 pc), adjacent, with similar kinematics and ages a unique and large association? Others?

Background

Sample definition

ROSAT All-Sky Bright Source Catalogue

Proper motions from Hipparcos or Tycho-2 Catalogues

(B-V) 0.6 (later than G0)

Excluding known RS CVn, W UMa, giants, etc (SIMBAD)

Excluding Mv < 2.0 (or L < 10 Lʘ ages > 5 Myr)

Goals

Li abundance

Metallicity

Radial and Rotational Velocities

Duplicity

Evolutionary stage

Instruments

FEROS (ESO - 1.52 m & 2.2m)

Coudé (OPD/LNA - 1.60m)

CORALIE (ESO - Swiss Euler Telescope)

Statistics

Southern ROSAT Sources

SACY [Hip + TYC & (B-V)0.6]

Observed objects (not sources)

Data from literature

9574

1953

1750

150

-70

+10

-10

-50

-30

=18

=6

=12

=0

-70

+10

-10

-50

-30

=18

=6

=12

=0

RESULTS Giants 17%

Dwarfs (IV & V) 83%

Young stars (*) 39%

Pleiades age 22%

Old stars 39%

SB

10%

16%

38%

(*) Includes dwarf stars later than M0

UVW from stars with

parallaxes

UVW from6D clustering

analysis

UVW taken from

literature

Concentration detected

around U0V0W0

Group/Association?

Age from Li strength or

Isochrone fitting

1st s

tep

– lo

ok f

or c

once

ntra

tion

in t

he U

VW

spa

ce

? 3.5 F

? km/s 30

VV

σ=

Out of ad-hoc XYZ constraints to the

member list?

Loop over all young objectsin the catalogue

Minimize:2)0(2)0(2)0(2),( WWVVUUisoVMVMpF

Starrejected

Yes

Add star toMember list

No

Compute newU0V0W0 using

new member list

2nd s

tep

- L

oo

p o

ver

cata

log

ue

un

til

con

verg

ence

is

reac

hed

Probabilities?New ad-hoc

XYZ constraints?New limits: F or σ?

COMPARISON OF THE AD-HOC CURVESTO BARAFFE MODELS

5 Myr

10 Myr

50 Myr100 Myr

Expansion of the Associations in X direction

Within β PicA

Concentration in the UVW space:

U=-10.1 V=-15.9 W=-9.1

The β Pic Association

46 Members

ʘ

ʘʘ

5 Myr

10 myr

70 myr

β Pic Association

β Pic AssociationN S

Concentration in the UVW space:U=- 9.6 V=-20.9 W=-1.3

U=-12.7 V=-21.9 W=-5.6

U=-10.5 V=-23.2 W=-4.3

The GAYA Complex:

Tuc-HorA: 36 Members

ColA: 27 Members

CarA: 21 Members

ʘ

ʘ

ʘ

5 Myr

10 Myr

30 Myr70 Myr

GAYA ComplexGreen Tuc-HorAWhite ColARed CarA

Concentration in the UVW space:

U=-10.5 V=-18.0 W=-4.9

The TW Hya Association

22 Members

ʘ

ʘ ʘ

TWA 20

5 Myr8 Myr

70 Myr

TW Hya Association

Concentration in the UVW space:

U=-11.0 V=-19.9 W=-10.4

The ε Cha Association

24 Members (4 from η Cha)

ʘ

ʘ ʘ

5 Myr

10 Myr

70 Myr

ε Cha AssociationRed Field MembersGreen η Cha C. MembersBlank Others η Cha Cluster

Concentration in the UVW space:

U=-13.6 V=-2.7 W=-9.4

The Octantis Association

11 Members

ʘ

ʘ ʘ

5 Myr

10 Myr

70 Myr

Oct Association

Concentration in the UVW space:

U=-22.0 V=-14.4 W=-5.0

The Argus Association

63 Members (35 from IC 2391)

ʘ

ʘ ʘ

Argus Association

5 Myr10 Myr

30 Myr70 Myr

Red Field MembersGreen IC 2391 Members

Concentration in the UVW space:

U=-6.8 V=-27.2 W=-13.3

The AB Dor Association

75 Members

ʘ

ʘ ʘ

AB Dor Association

5 Myr

10 Myr

70 Myr

AB Dor Association

N S

Association N Age U σ V σ W σ EXP

β Pic 46 10 -10.1 2.1 -15.9 0.8 -9.1 0.9 Y

Tuc- Hor 36 30 -9.6 0.9 -20.9 0.8 -1.3 0.9 Y

Col 27 30 -12.7 1.1 -21.9 0.8 -5.6 0.9 Y

Car 21 30 -10.5 0.4 -23.2 0.8 -4.3 1.6 Y?

TW Hya 22 8 -10.5 0.9 -18.0 1.5 -4.0 0.9 Y

ε Cha 24 6 -11.0 1.2 -19.9 1.2 -10.4 1.6 N?

Oct 11 10 -13.6 2.5 -2.7 1.4 -9.4 1.0 Y

Argus 63 40 -22.0 0.3 -14.4 1.3 -5.0 1.3 N

AB Dor 75 70 -6.8 1.3 -27.2 1.1 -13.3 1.5 N

-50 0 50 100 150 200

-200

-150

-100

-50

0

50

LCC

Y p

c

X pc

-50 0 50 100 150 200

-200

-150

-100

-50

0

50

E C ha

Y p

c

X pc

-50 0 50 100 150 200

-200

-150

-100

-50

0

50

TWA

Y p

c

X pc

-50 0 50 100 150 200

-200

-150

-100

-50

0

50

TW E

Y p

c

X pc

-50 0 50 100 150 200

-200

-150

-100

-50

0

50

UC L

Y p

c

X pc

-50 0 50 100 150 200

-200

-150

-100

-50

0

50

US

Y p

c

X pc

-50 0 50 100 150 200

-200

-150

-100

-50

0

50

Rho Oph

Y p

c

X pc

-50 0 50 100 150 200

-200

-150

-100

-50

0

50

CrA

Y p

c

X pc

-50 0 50 100 150 200

-200

-150

-100

-50

0

50

B Pic

Y p

c

X pc

-50 0 50 100 150 200

-200

-150

-100

-50

0

50

GAYA 1

Y p

c

X pc

-50 0 50 100 150 200

-200

-150

-100

-50

0

50

GAYA 2

Y p

c

X pc

-50 0 50 100 150 200

-150

-100

-50

0

50

100

LCC

Z p

c

X pc

-50 0 50 100 150 200

-200

-150

-100

-50

0

50

E C ha

Z p

c

X pc

-50 0 50 100 150 200

-150

-100

-50

0

50

100

TWA

Z p

c

X pc

-50 0 50 100 150 200

-150

-100

-50

0

50

100

TW E

Z p

c

X pc

-50 0 50 100 150 200

-150

-100

-50

0

50

100

UC L

Z p

c

X pc

-50 0 50 100 150 200

-150

-100

-50

0

50

100

US

Z p

c

X pc

-50 0 50 100 150 200

-150

-100

-50

0

50

100

Rho Oph

Z p

c

X pc

-50 0 50 100 150 200

-150

-100

-50

0

50

100

CrA

Z p

c

X pc

-50 0 50 100 150 200

-150

-100

-50

0

50

100

B Pic

Z p

c

X pc

-50 0 50 100 150 200

-150

-100

-50

0

50

100

GAYA 1

Z p

c

X pc

-50 0 50 100 150 200

-150

-100

-50

0

50

100

GAYA 2

Z p

c

X pc

-2 5 -2 0 -1 5 -1 0 -5 0 5

-3 0

-2 5

-2 0

-1 5

-1 0

-5

0

SACY

GAYA 1 OctA GAYA 2 AnA TW A ArgA YS SA US E Cha LC C B Pic TW A E

V k

m/s

U km /s

-2 5 -2 0 -1 5 -1 0 -5 0 5

-2 0

-1 5

-1 0

-5

0

5

1 0

SACY

GAYA 1 OctA GAYA 2 AnA TW A ArgA YS SA US E Cha LC C B Pic TW A E

W k

m/s

U km /s

-3 0 -2 5 -2 0 -1 5 -1 0 -5 0

-2 0

-1 5

-1 0

-5

0

5

1 0

SACY

GAYA 1 OctA GAYA 2 AnA TW A ArgA YS SA US E Cha LC C B Pic TW A E

W

km/s

V km /s

Insights

The distribution of young stars in the solar neighborhood is patchy, forming huge kinematical associations.

We recognize at least 14 young associations in the SACY database (there are five more possible associations to verify) .