NIR surface photometry of nearby spiral galaxies
Nieves CastroCastro-Rodríguez1, Francisco Garzón1,2 & Berto CastroCastro-Rodríguez 2
1Instituto
de Astrofísica de Canarias, 38200–
38200–La Laguna, Tenerife
de Astrofísica, Universidad de La Laguna, Tenerife
2Departamento
The results of an observational programme aimed at mapping a sample of face-on spiral galaxies in the NIR are presented.
The data were taken in the broad band J (1.2 µm) and (2.2 µm) filters. The targets are selected mainly according to their size
and brightness in order to suit the characteristics of the CAIN 2D NIR camera on the 1.5-m Carlos Sánchez Telescope
(Tenerife, Spain).
The primary scientific goal is to provide a comprehensive and uniform database of the main structural and photometric
parameters of the sample members from NIR surface photometry. To this end, elliptical isophotal fitting was performed on
each galaxy image to extract information about the size and location of its morphological components and provide the
azimuthally averaged radial brightness profile. Analytical functions for each component's brightness distribution were then
used to match that profile, and their functional parameters obtained from the global fitting. We have used a 1D structural
descomposition and the 2D, whose first results are displayed in this poster for comparison. The next step in our work will
be the determination of the 3D luminosity distribution and hence the mass distribution, via direct inversion of the Abel
integral of the luminosity density.
Galaxy
RA
[h]
NGC 3344 10.72
NGC 3686 11.46
NGC 3938 11.88
NGC 3953 11.89
NGC 4254 12.31
NGC 4303 12.36
NGC 4314 12.37
NGC 5248 13.62
NGC 6384 17.54
NGC 7479 23.08
Surface photometry of external galaxies in the optical domain has burgeoned in recent decades with advent
of large format CCD arrays and the popularity of the 2D optical cameras. Data have been amassed since
then for a wide range of astrophysical studies, from morphological classification (van der Kruit & Searle
1981, 1982) to stellar population characterization (de Jong 1996); from star formation research (Kennicutt
1989) to the investigation of the ISM in external galaxies (Valentijn 1994). The situation is much poorer in
other wavelength regimes. The near infrared (NIR) domain is particularly interesting in this respect since
in this range the flux is largely dominated by the direct stellar radiation while drastically reducing the
general extinction. In addition, NIR colours are very sensitive to population changes in the galaxy (Peletier
et al. 1994; de Jong & van der Kruit 1994).
We have recently started an observational programme aimed at producing a database of NIR infrared
images of spirals galaxies, with several primary objectives in mind:
Dec
[deg]
24.92
17.22
44.12
52.32
14.41
4.47
29.89
8.88
7.06
12.32
Type
SABbc
SBbc
SAc
SBbc
SAc
SABbc
SBa
Sbc
SABbc
SBc
T
logD25
4.0
4.1
5.1
3.9
5.2
4.0
1.0
4.0
3.6
4.4
PA
MB Incl.
[0.1'] [deg]
10.49
15 11.96
52 11.04
13 10.84
10.42
162 10.18
11.41
110 11.00
30 11.60
25 11.77
1.85
1.48
1.69
1.88
1.72
1.79
1.59
1.75
1.69
1.61
mag
17.6
40.8
12.9
63.3
32.0
19.2
19.2
50.5
59.9
36.4
D
[Mpc]
9.3
14.2
11.4
12.6
14.8
19.4
12.5
14.8
24.1
34.7
Tab. 1 First sample of galaxies studied in Castro-Rodríguez &
Garzón, 2003.
* to characterize the presence of the relevant morphological components and compare, whenever
possible, their structural parameters with those obtained in the optical.
* to check their morphological classification.
* to investigate trends in structural parameters with morphological type.
* In addition, with the existing data base, we will also attempt a direct determination of the
luminosity and mass distribution, via a direct inversion method of the Abel integral, already
developed and treated for elliptical galaxies (Simonneau et al. 1993).
* We will also enlarge the target list with the inclusion of several objects with nuclear activity to
check for relationships between the inner structures and the strength of that activity (Graham et al.
2001).
Cration of a NIR spiral
Galaxies data base
The galaxies presented in this work have been selected primarily according to their isophotal D25 diameter,
as listed in the RC3 (de Vaucouleurs 1991), and their brightness, both being considered within the suitable
range for testing the feasibility of the project. We included only spirals in this first sample since they
exhibit a wider range of morphological structures.
One of our main purposes is to investigate the presence
and geometrical parameters of the principal structural
components that contribute to the observed surface
brightness. Radial profiles are the appropriate tool for
this purpose and can be easily constructed with the
technique of ellipse fitting. The first results are
presented in Castro-Rodríguez & Garzón 2003 of a
sample of ten galaxies (see table 1).
Fig. 2
Tab. 3 Similar parameters than in Tab. 2 but in 2D
Fig. 1
Once the radial profiles have been obtained and the
general parameters calculated, we can now proceed with
the decomposition of the averaged brightness profile into
different structural components, each with a separate
contribution to the observed flux. Previous NIR
decomposition can be found in de Jong (1996),
Moriondo et al. (1998) and references therein. For the
different component identification we have followed the
technical approach of Prieto et al. (2001) where the
changes in the radial profiles of ellipticity and position
angle are used to identified the radial interval over which
the given component extends.
0,74
0,75
0,98
1
1,38
0,74
1,27
1,03
0,92
1,09
M_disc
1
1
1
1
1
1
1
1
1
1
h
18,35
19,26
18,24
19,6
17,93
18,67
20,52
18,05
19,36
20,16
M_bar
41,77
30,94
29,7
64
30,33
69,64
45,06
29,19
58
60,3
a
b
18,3
19,05
12
16
19,6
44
18,05
19,95
26
73
17,95
18,55
25,5
50
M_disc
h
18,513
18,29
18,41
18,21
17,53
18,22
20,57
17,89
18,96
19,28
M_bar
46,63
25,9
32,42
61,69
34,4
55,33
47,03
39,48
53,01
49,37
ax
17,93
19,45
30,47
18,11
20,71
18,58
19,48
41,17
18,11
18,01
10,24
5,74
1,00E+114
44,39
90,66
40,42
58,31
1,00E+25
11,84
50,93
bx
ay
3,36
1,16
1,00E+23
4,6
194,2
11,08
8,36
3,00E+28
7,62
10,1
by
7,6
26,7
72,33
8,9
2,04
11,92
11,66
4,00E+36
23,93
6,07
2,03
6,89
1,6
4,7
6,00E+84
3,93
4,16
9,00E+40
11,54
4,7
Barred
YES
YES
NO
YES
NO
YES
YES
NO
YES
YES
The next goal was develop the 2D analysis. We
have used the Levenberg-Marquad method.
We have developed an iterative algorithm to deduce from the 2-D brightness distribution the
contributions of bulge, disc and bars. Now, we are working in the non axisimetric structures (bars, triaxial bulges, etc). The first results obtained
for the sample of ten galaxies from Castro-Rodríguez & Garzón 2003 (but in 2D), are showed in the Tab. 3 and Fig.3. Some galactic parameters in
the 2D differ from the 1D analysis because of the the spiral arms (see Tab.2 and Tab.3). It is difficult to fit the end of the bar when there is a strong
stellar formation at the beginning of the arms. We are improving now this method (Castro-Rodríguez et al. 2004).
The figure 1, represents the galaxy NGC 7479 and his 1D
descomposition in its different structural components
(disc, bulge and bar). Our procedure to fit the several
morphological components to the measured brightness
profile is similar to that described in Prieto et al. (2001).
Once the components have been identified in the radial
profiles of several parameters coming from the ellipse
fitting, we first fix the disc in the outer parts of the
galaxy, where contamination from other components can
be neglected. Next, this disc model is subtracted from the
original profile and we fit the bulge to the residuals with
the best Sersic law (n=1-4). These operations are iterated
until convergence, defined as the difference between two
consecutive set of parameters being less than the
measured noise, is reached.
n
n
Barred
4 YES
5 YES
NO
4 YES
NO
9 YES
7 YES
NO
2,5 YES
7,5 YES
2D structures of NGC4254 in the J band
From left to right: original image, model, residual structures
(Castro-Rodríguez, B. el al., 2004)
Fig. 3
Tab. 2. Parameters of the differnt structures of the galaxies. We have used Sersic profiles
for the bulge, exponential discs and flat bars (see Castro-Rodríguez & Garzón 2003).
The next steps are:
*to continue with the NIR database adding new galaxies (see Fig. 2).
*to improve the 2D fitting, and try to model the spiral structure.
*to compare the parameters obtained for the center of the galaxies with the
nuclear activity and ... With the optical results of Graham et al. 2001. They
found that exists a evidence for a strong correlation between the
concentration
of bulges and the mass of their central supermassive black hole.
Castro-Rodríguez, N., & Garzón, F 2003, A&A, 411, 55
Castro-Rodríguez, B., Garzón, F, & Castro-Rodríguez, N 2004, in preparation
Van der Kruit, P. C., & Searle, L. 1981, A&A, 95, 116
Graham, Alister W., Erwin, Peter, Caon, N., & Trujillo, I. 2001, A pJ, 563L, 11
De Jong, R. S. 1996a, A&A, 118, 557
De Jong, R. S., & van der Kruit, P. C. 1994, A&AS, 106, 451
Kennicutt, R. C. 1989, ApJ, 344, 685
Moriondo, G., Giovanardi, C., & Hunt, L. K. 1998, A&AS, 130, 81
Peletier, R .F., Valentijn, E. A., Moorwood, A. F. M., & Freudling, W. 1994, A&AS, 108, 621
Prieto, M., Aguerri, J. L., Varela, A. M., & Muñoz-Tuñón, C. 2001, A&A, 367, 405
Simmoneau, E., Varela, A. M., & Munoz-Tunon, C. 1993, JQSRT, 49, 149
Valentijn, E. A. 1994, MNRAS, 266, 614
Van der Kruit, P. C., & Searle, L. 1982, A&A, 110, 79
Varela, A. M., Muñoz-Tuñón, C., & Simmoneau, E. 1996, A&A, 306, 381
de Vaucouleurs, G. 1991, RC3-Third Reference Catalogue of Bright Galaxies (Springer-Verlag)