The properties of ISOLATED SPIRAL GALAXIES
Isabel Márquez 1 , Josefa Masegosa 1 , Mariano Moles 2 , Jesús Varela 2 , Daniela Bettoni 3 and Giuseppe Galletta 4
1
Instituto de Astrofísica de Andalucía (CSIC), Granada (Spain)
2
Instituto de Matemáticas y Física Fundamental (CSIC), Madrid (Spain)
3
4
Osservatorio Astronomico di Padova (Italia)
Dipartamento di Astronomia, Universitá di Padova
(Italia)
KEY QUESTIONS:
QUESTIONS:
KEY
Importance of
of mild
mild gravitational
gravitational interactions
interactions on
on the
the evolution
evolution of
of spiral
spiral
Importance
galaxies.
galaxies.
Do they
they change
change their
their structure?
structure?
•• Do
RESULT 11
RESULT
Isolatedgalaxies
galaxiestend
tendto
tobe
beof
oflater
laterHubble
Hubbletypes
types
Isolated
andlower
lowerluminosity
luminositythan
thaninteracting
interactinggalaxies
galaxies
and
Is the
the Star
Star Formation
Formation History
History affected?
affected?
•• Is
ISOLATED Ss
Sample 1
Sample 2
Isolated
Perturbed
MILDLY NTERACTING Ss
THE SAMPLES
SAMPLES AND
AND THE
THE DATA
DATA
THE
The results
results presented
presented in
in this
this contribution
contribution are
are based
based in
in the
the study
study of
of two
two samples:
samples:
The
1) 111
111 spiral
spiral galaxies
galaxies with
with aa well
well studied
studied environmental
environmental status
status (from
(from isolation
isolation to
to mild
mild
1)
interaction with
with satellites
satellites or
or companions)
companions) and
and with
with long
long slit
slit spectroscopic
spectroscopic data
data
interaction
obtained by
by us
us (Márquez
(Márquez && Moles
Moles 1996
1996 and
and Márquez
Márquez et
et al.
al. 2002).
2002). 93
93 galaxies
galaxies
obtained
were selected
selected from
from the
the CfA
CfA catalogue
catalogue (Huchra
(Huchra et
et al.
al. 1999)
1999) ,, being
being brighter
brighter
were
13, smaller
smaller than
than 4’
4’ in
in diameter,
diameter, having
having inclinations
inclinations between
between 32
32ºº and
and
than m
mBB == 13,
than
and with
with no
no CfA
CfA companions
companions within
within 0.5
0.5 Mpc
Mpc in
in proyected
proyected distance
distance and
and 500
500
73ºº and
73
km/s
in
redshift
difference.
13
spirals
in
7
pairs
from
Karachentsev’s
(1972)
km/s in redshift difference. 13 spirals in 7 pairs from Karachentsev’s (1972)
catalogue of
of isolated
isolated pairs
pairs were
were also
also selected.
selected. Only
Only those
those galaxies
galaxies with
with still
still
catalogue
recognizable and
and well
well defined
defined spiral
spiral morphology
morphology were
were retained.
retained.
recognizable
Sample 1
Sample 2
2) 196
196 isolated
isolated and
and 129
129 perturbed
perturbed galaxies
galaxies selected
selected from
from the
the CfA
CfA catalogue
catalogue and
and
2)
with aa determination
determination of
of the
the nearest
nearest neighbor
neighbor given
given by
by ff parameter
parameter (see
(see below)
below) by
by
with
using the
the information
information in
in LEDA
LEDA catalogue*
catalogue* (see
(see Varela
Varela et
et al.
al. 2004)
2004) for
for details.
details.
using
The
properties
given
in
the
LEDA
database
are
compared
between
the
two
The properties given in the LEDA database are compared between the two
samples.
samples.
Catalogueby
byPaturel,
Paturel,complete
completeto
tomB
mB==18
18
**Catalogue
THE ISOLATION
ISOLATION STATUS
STATUS
THE
RESULT 33
RESULT
Tully--Fisher
Fisherrelation
relationsignificantly
significantlyless
lessscattered
scatteredfor
forisolated
isolatedgalaxies
galaxies
Tully
The presence
presence of
of perturbing
perturbing companions
companions has
has been
been investigated
investigated by
by means
means of
of the
the
The
parameter:
parameter:
f = 3 ⋅ log(r/D)
with
with
TRULY ISOLATED
ISOLATED
TRULY
+ 0.4 ⋅ (m − m p )
radius of
of the
the target
target galaxy
galaxy
rr :: radius
D :: distance
distance to
to the
the perturber
perturber
D
m: magnitude
magnitude of
of the
the target
target
m:
magnitude of
of the
the perturber
perturber
mpp:: magnitude
m
(INT == 1),
1),
(INT
f ≤ −4
POSSIBLY INTERACTING,
INTERACTING, (INT
(INT == 2),
2),
POSSIBLY
INTERACTING GALAXIES,
GALAXIES, (INT
(INT == 3),
3),
INTERACTING
(24 in
in sample
sample 1)
1)
(24
f > −4
f > −4
with no
no zz
with
(43 in
in sample
sample 1)
1)
(43
RESULTS
RESULTS
1. Isolated
Isolated galaxies
galaxies tend
tend to
to be
be of
of later
later Hubble
Hubble types
types and
and lower
lower luminosity
luminosity
1.
than interacting
interacting galaxies
galaxies ((samples
and 22).
S0s are
are significantly
significantly more
more
than
samples 11 and
). S0s
abundant among
among perturbed
perturbed systems
systems as
as do
do barred
barred spirals
spirals ((sample
abundant
sample 22).
).
2. Rotation
Rotation curves
curves of
of isolated
isolated galaxies
galaxies tend
tend to
to be
be flatter
flatter ((sample
1)
2.
sample 1)
3. The
The scatter
scatter of
of the
the Tully
Tully -- Fisher
Fisher relation
relation is
is significantly
significantly lower
lower for
for
3.
isolated galaxies
galaxies ((samples
and 2)
2)
isolated
samples 11 and
4. Earlier
Earlier type
type spirals
spirals have
have higher
higher nuclear
nuclear metallicities
metallicities ((sample
1)
4.
sample 1)
5. [NII]/Ha
[NII]/Ha ratios
ratios larger
larger for
for the
the disks
disks of
of interacting
interacting galaxies
galaxies ((sample
1)
5.
sample 1)
6. Tight
Tight correlation
correlation between
between Z
Z and
and GG (inner
gradient of
of the
the RC)
RC) ((sample
1)
6.
inner gradient
sample 1)
((inner
7. Isolated
Isolated galaxies
galaxies appear
appear smaller
smaller and
and fainter,
fainter,
with bluer
bluer color
color indices.
indices.
7.
, with
.
fainter
indices
They also
also have
have less
less molecular
molecular gas
gas and
and smaller
smaller L(FIR)/LB
L(FIR)/LB.
The biggest
biggest
They
)/LB.. The
L(FIR
differences are
are for
for S=s
S=s and
and early
early spirals
spirals ((sample
2)
differences
sample 2)
RESULT
RESULT 44
Earlier
Earliertype
typespirals
spiralshave
havehigher
highernuclear
nuclear
metallicities
metallicities
RESULT
RESULT 55
[NII]/Hα
[NII]/Hα
ratioslarger
largerfor
forthe
thedisks
disksof
of
[NII]/Hαratios
interacting
interactinggalaxies
galaxies
MAIN CONCLUSIONS
CONCLUSIONS
MAIN
not only
only strongly
strongly gravitational
gravitational interactions
interactions can
can be
be effective
effective in
in
-- not
modifying both
both structural
structural and
and star
star formation
formation properties
properties of
of Ss:
Ss:
modifying
:
Ss
MILD INTERACTIONS
INTERACTIONS also
also have
have noticeable
noticeable effects
effects and
and should
should
MILD
be therefore
therefore considered
considered when
when analysing
analysing big
big samples
samples of
of field
field Ss
Ss
be
gravitational interaction
interaction in
in aggregates
aggregates may
may produce
produce evolution
evolution
-- gravitational
from late
late S,
S, relatively
relatively faint
faint and
and low
low mass
mass galaxy,
galaxy,
toward
from
, toward
galaxy
earlier more
more luminous
luminous and
and massive
massive S
S and
and SO,
SO, also
also favoring
favoring the
the
earlier
formation of
of bars
bars in
in early
early Ss
Ss and
and S0s
S0s
formation
present day
day isolated
isolated spirals
spirals would
would be
be the
the left
left over
over fragments
fragments
-- present
in the
the early
early process
process of
of galaxy
galaxy formation
formation
in
SAMPLE 1: Márquez, Masegosa, Moles, Varela, Bettoni, Galletta 2002, A&A 393, 389
SAMPLE 2: Varela, Moles, Márquez, Galletta, Masegosa & Bettoni 2004, A&A 420, 873