Brown D

warf Can

didates

in the Serpen

s Core

C. Eiroa –Universidad

Autónoma de Mad

rid

A. A. Djupvik –

Nordic O

ptica

l Telesco

pe

M. M. Casali –ESO

Outline

●Short description of the Serpen

s cloud &

core

●Embed

ded

population + spatial distribution

●Near-IR

cluster

--Near-IR

diagrams

●BD can

didates

Serpen

s Cloud

# N

earby dark cloud of several deg

rees in size; part of the Aquila rift

--lII = 32o, bII= 5

o; d ≈

250 pc

DSS –

R plate

IRAS 60 µm (Zhan

g et al. 1988)

Serpen

s Core

# H

2CO core: ~

6 arcmin in diameter �

~0.5 pc

# Large scale CO molecu

lar outflow

Loren et al. (1979)

DSS -R plate

Bally &

Lad

a, 1983

SRN

Serpen

s co

re: 100 µm,1.3 m

m &

CO

Zhan

g et al. 1988

Kaas et al. 2004

McM

ullin et al. 2000

# C

ore structured into two sub-clumps

# Embed

ded

stellar population sh

ows different ev

olutionary properties

Embed

ded

Population

# O

ptical, nea

r-IR

, mid-IR, su

bmm, mm, cm

+ X

-Ray

studies provide

different views of the em

bed

ded

population

# V

ery rich

star form

ation activity

3mm: Testi &

Sargen

t (1998)

J+H+K: Kaas (1999)

Embed

ded

Population

# 26 3 m

m cores (T

esti &

Sargen

t, 98)

# 11 submm sources (Casali et al. 93, W

hite et al 95, Dav

is et al. 99)

# 76 ISO sources (6.7 + 14.3 µm)(K

aas et al. 2004)

# 188 nea

r-IR

sources (Eiroa & C

asali 89, 92, Horrobin et al 97, Sogaw

a et al 97,

Giovan

netti et al. 98, Kaa

s 99, Klotz et al. 04, Eiroa et al. 05)

# 18 0.9 µm sources (Gómez

de Castro et al. 87, Giovan

netti et al. 98)

# 16 V

LA sources (Smith et al. 99, Eiroa et al. 05)

# 14 X

MM

X-R

ay sources (Preibisch

98, 03)

�Very Y

oung Population

(ISOCAM

comparison)

Class I C

lass II C

lass III

Serpen

s 20 56 (13+43) 5 !! K

aas et al. 2004

Ophiuch

us 16 123 77 Bontemps et al. 2001

Cham

aeleon 46 19 Persi et al. 2000

Class II ISO sources: Age

Log L Log L

Kaa

s et al (2004)

# K

aas et al. 04: Luminosity function of the 43 ISO C

lass II so

urces on the

basis of the IS

O 6.7 µm flux and A

V from nea

r-IR

mag

nitudes

--Comparison w

ith different IM

Fs

(Kroupa et al. 93, Scalo 98) plus

evolutionary track

s (D

’Antona

& M

azzitelli 98, Baraffe et al. 98)

�Best fit: 2 M

yr

# Lodieu et al. 02 estim

ate ~ 3.5 M

yr

for BD-S

er1 (EC 61)

Distribution of Serpen

s YSOs

# M

ost sources located in the 6’ x 6’ ce

ntral (mm) co

re

Dots: nea

r-IR

cources

Crosses: ISO C

lass II

Trian

gles: ISO C

lass

I

Hex

agons: smm sources

Filled trian

gles: m

m cores

--but clear

differences

betwee

n the

NW

and SE

clumps

Detailed D

istribution

�Near-IR

sources found across the

whole core, but more concentrated

towards the SE clump

�Class II ap

prox. follows same tren

d

�Class I, Class O

: ap

prox. same

number in both SE and N

W clumps

�mm cores more common in the NW

clump

�Star form

ation is cu

rren

tly

taking place

in both clumps;

but more active in the NW

one

�Star form

ation w

as m

ore

efficien

t or beg

an earlier in the SE clump

�Sev

eral star form

ation phases hav

e taken

place

Dots: nea

r-IR

cources

Crosses: ISO C

lass II

Trian

gles: ISO C

lass

I

Hex

agons: smm sources

Filled trian

gles: m

m cores

Near-IR

population in the Core

�∼

1000near-IR

sources detected in the ce

ntral (~ 8' x

8') core

# Total number of iden

tified

Serpen

s nea

r-IR

sources: 188

# M

ain iden

tification criteria for Serpen

s mem

bership:

--near-IR

exce

sses

--variability

--asso

ciation w

ith neb

ulosity

--Eiroa & C

asali, 92: 51 sources

--Sogaw

a et al., 97: 38 sources

--Giovan

netti et al, 98 : 55 sources

--Kaa

s, 99: 55 sources

--Kaa

s et al. 2004: 8 sources

--Klotz et al. 04(*) : 14 sources

--Eiroa et al. 05: 13 sources

(*) The dee

p survey

(K ∼

19 m

ag) by K

lotz et al. 04 m

ainly extends to an area 5'x10' towards the SW

of the co

re

where ex

tinction is su

bstan

tially lower. Sev

eral thousandsof so

urces are detected

(H-K

,J-H

) diagram

IR sources embed

ded

in the co

re Core + K

lotz et al. 04 sources

Near-IR

diagrams

# C

olor-mag

nitude diagrams of em

bed

ded

sources in the Serpen

s co

re.

--~ 40 sources below 0.07 M

sun, down to planetary m

asses

�20% of the Serpen

s nea

r-IR

objects

# Isoch

rones from B

araffe et al. 03

BD C

andidates: Near-IR

Diagrams

# C

olor-mag

nitude an

d color-co

lor diagrams of BD

candidates

•28 sources show near-IR

excesses

•16 sources are variable (typically ∆

K ~ 0.5 m

ag, much

larger than

typical 3

σerrors)

Square: B

D-Ser1 (EC61)

Suggested B

Ds:

--Kaas et al. 04 (ISO, dots)

--Klotz et al. 04 (nea

r-IR

,

squares)

Hex

agons: B

D can

didates

(this w

ork)

BD can

didates: K-ban

d histogram

# Since

the BD can

didates are faint, importan

t to chec

k that they

are

“real”:

•most B

D can

didates w

ell ab

ove the co

mpleteness limit of the near-IR

studies

•22 sources common in different works

•12 sources detected in sev

eral epoch

s

by K

aas (1999)

•8 sources only detected in one work

# D

ifficu

lt to estim

ate the intrinsic

K-ban

d distribution becau

se of:

i) Color ex

cess

ii) Variability

⇒Both i)an

d ii)mak

e it difficu

lt

to estim

ate ex

tinction

BD C

andidates: Spatial distribution

# B

D can

didates located towards

the less obscured part of the

core, av

oiding the very den

se

NW

clump and the den

sest part

of the SE clump.

Near-IR

: diagrams of Klotz's sources

and Serpen

s em

bed

ded

objects

Lodieu’s B

D-SEr1 Spectrum

Summary

•~ 20% of the near-IR

YSOs detected (so

far) in the

Serpen

s co

re could be brown dwarfs

•Age: 2 –4 x 106years

•Can

didates nee

d spectroscopic confirm

ation

•They

could rep

resent the lower m

ass (substellar) end of

a very young Y

SO cluster