Structure and dynamics of the central regions of disk galaxies
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Structure and dynamics of the central regions of disk galaxies. Ph.D. Supervisors: José Alfonso López Aguerri (IAC) Enrico Maria Corsini (Univ. Padova). Jairo Méndez Abreu Post-Doc Consolider Estallidos (IAC). Thesis work conducted at.

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Structure and dynamics of the central regions of disk galaxies

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Structure and dynamics of the central regions of disk galaxies

Structure and dynamics of the central regions of disk galaxies

Ph.D. Supervisors: José Alfonso López Aguerri (IAC)

Enrico Maria Corsini (Univ. Padova)

Jairo Méndez Abreu

Post-Doc Consolider Estallidos (IAC)

Thesis work conducted at

Università di Padova Universidad de La Laguna INAF-Osservatorio di Padova


Structure and dynamics of the central regions of disk galaxies

Bulges

Bars

Introduction

  • What do we mean by “central regions” of disk galaxies?


Introduction

Eggen et al. 1962

Sandage 1990

Gilmore & Wyse 1998

Kauffmann 1996

Baugh et al. 1996

Cole et al. 2000

Classical Bulges

Aguerri et al. 2001

Fu et al. 2003

Eliche-Moral et al. 2006

Athanassoula 1992

Heller & Shlosman 1994

Shen & Sellwood 2004

Disk-like Bulges

Raha et al. 1991

Debattista et al. 2004

Martínez-Valpuesta et al. 2006

Boxy/Peanut Bulges

Introduction

Formation Theories for Bulges


Introduction1

Introduction

  • Bars:

1. Quasi-elliptical structures which are present in most of the disk of spiral galaxies.(Marinova & Jogee 2007, Aguerri et al. 2009)

3. Drive gas efficiently from the outer disk to the central regions of galaxies(Kormendy & Kennicutt 2004)

2. The most important internal factor in redistributing the baryonic and dark matter angular momentum(Weinberg 1985, Debattista & Sellwood 2000, Athanassoula 2003)


Introduction2

Introduction

Aims of this thesis

  • How and where did bulges form?

  • How and where did bars form?

  • Is the formation of bulges and bars intimately linked?

Observational point of view


Gasp2d galaxy surface photometry 2d a new two dimensional photometric decomposition code

GASP2D v1.0:

Two components (Bulge + Disk)

Méndez-Abreu, J., Aguerri, J. A. L., Corsini, E. M., Simonneau, E., “Structural properties of disk galaxies. I. The intrinsic equatorial ellipticity of bulges”, 2008, A&A, 478 ,353

GASP2D v2.0:

Three components (Bulge + Bar + Disk)

Méndez-Abreu, J. et al., 2009, in preparation

GASP2D (GAlaxy Surface Photometry 2D)A new two-dimensional photometric decomposition code


Gasp2d galaxy surface photometry 2d

GASP2D(GAlaxy Surface Photometry 2D)

  • Three independent reference systems (Ellipticity and Position Angle)

  • Parametric Flux distributions;

    Bulge - Sérsic Profile (Sérsic 1968)

    Disk - Exponential profile (Freeman 1970)

    - Ferrers (Ferrers 1877)

    Bar - Flat (Prieto et al. 1997)

    - Elliptical (Freeman 1966)


Structure and dynamics of the central regions of disk galaxies

GASP2D (GAlaxy Surface Photometry 2D)

Advantages with respect to other codes

  • Realistic parametric description of the bar SB

  • Works automatically

  • Flexibility to create mask


Structure and dynamics of the central regions of disk galaxies

GASP2D (GAlaxy Surface Photometry 2D)

Outputs :

1. File with the best-fitted parameters + χ2 + B/D

2. Three fits images: Best model + Residuals + Masks


Structure and dynamics of the central regions of disk galaxies

GASP2D v2.0


Structure and dynamics of the central regions of disk galaxies

GASP2D (GAlaxy Surface Photometry 2D)

Already used and tested in different works:

  • Méndez-Abreu 2008, PhD thesis

  • Méndez-Abreu et al. 2008, A&A, 478, 353

  • Méndez-Abreu et al. 2009, in preparation

  • Morelli et al. 2008, MNRAS, 389, 341

  • Pizzella et al. 2008, MNRAS, 387, 1099

  • Beifiori et al. 2008, ApJ, accepted, arXiv0809.5103

  • Sánchez-Janssen et al. 2009 in preparation

  • Ascaso et al. 2009 in preparation


Structure and dynamics of the central regions of disk galaxies

Structure of disk galaxiesScaling relation of bulges and disksMéndez-Abreu, J., Aguerri, J. A. L., Corsini, E. M., Simonneau, E., “Structural properties of disk galaxies. I. The intrinsic equatorial ellipticity of bulges”, 2008, A&A, 478,353

Sample selection

2MASS XSC - 148 galaxies

  • S0 ≤ Hubble type ≤ Sb ;

  • Unbarred galaxies (RC3) ;

  • JT < 10 mag ;

  • i < 65° ;

  • |bG|< 30° .


Structure and dynamics of the central regions of disk galaxies

Faber-Jackson relation

Fundamental Plane

Classical bulges

Structure of disk galaxiesScaling relation of bulges and disks

Bulge parameters

and correlations


Structure and dynamics of the central regions of disk galaxies

Hierarchical

merger

Secular evolution

Structure of disk galaxiesScaling relation of bulges and disks

Bulge and

disk interplay


Structure and dynamics of the central regions of disk galaxies

Structure of disk galaxiesScaling relation of bulges and disks

Conclusions:

  • Scaling relations alone are not able to distinguish between bulges formed by dissipative collapse, hierarchical merging or secular evolution.


Structure and dynamics of the central regions of disk galaxies

3D Shape of BulgesThe intrinsic equatorial ellipticityMéndez-Abreu, J., Aguerri, J. A. L., Corsini, E. M., Simonneau, E.,“Structural properties of disk galaxies. I The intrinsic equatorial ellipticity of bulges”, 2008, A&A, 478,353

1. Bulges consist of a series of concentric, coaxial isodensity ellipsoidal shells ;

2. Equatorial plane of the bulge coincides with the equatorial plane of the disk ;

3. Disk are circular giving us the line of nodes .

Hyphotesis :


Structure and dynamics of the central regions of disk galaxies

a

C

b

δ

B

Line of nodes

A

3D Shape of BulgesThe intrinsic equatorial ellipticity

Projection of triaxial ellipsoids.

Direct problem

Inverse problem

Line of Sight

(θ, φ)


Structure and dynamics of the central regions of disk galaxies

3D Shape of BulgesThe intrinsic equatorial ellipticity

Projection of triaxial ellipsoids. Inverse problem

Simonneau et al. (1998)

where


Structure and dynamics of the central regions of disk galaxies

IC 4310

3D Shape of BulgesThe intrinsic equatorial ellipticity

Individual statistic

The PDF of having an intrinsic equatorial ellipticity

is given by

where


Structure and dynamics of the central regions of disk galaxies

About 80% of bulges in unbarred S0-Sb galaxies are triaxial ellipsoids.

The mean axial ratio in the equatorial plane is <B/A>=0.85.

There is no significant dependence of the PDF on the morphology, light concentration, and luminosity of bulges

3D Shape of BulgesThe intrinsic equatorial ellipticity

Global Statistics


Structure and dynamics of the central regions of disk galaxies

Properties of Bars in the Nearby UniverseAguerri, J. A. L., Méndez-Abreu, J., Corsini, E. M., “The population of barred galaxies in the local universe. I Detection and characterisation of bars”, 2009, accepted in A&A, arXiv0901.2346

Sample selection

SDSS fifth data release (SDSS- DR5) ~3000 galaxies

  • Redshift between 0.01 < z < 0.04 ;

  • Absolute magnitude Mr< -20 ;

  • Inclination i < 60° ;

  • Exclude disturbed/interacting galaxies .


Structure and dynamics of the central regions of disk galaxies

Properties of Bars in the Nearby Universe

Methods for detecting and analyzing bars:

Ellipse fitting: - Local maximum in the (Δε)

- Constant position angle (ΔPA)

Fourier analysis: - Local maximum in the Δ(I2/I0)

- Constant phase angle (Δφ2)


Structure and dynamics of the central regions of disk galaxies

1. Bar fraction

2. Bar length

3. Bar strength

Bar properties :

Properties of Bars in the Nearby Universe


Structure and dynamics of the central regions of disk galaxies

Properties of Bars in the Nearby Universe

Bar fraction

Ellipse fitting45% of disk galaxies are barred

32% of lenticular galaxies are barred

55% of early-type spiral galaxies are barred

52% of late-type spiral galaxies are barred


Structure and dynamics of the central regions of disk galaxies

Properties of Bars in the Nearby Universe

Bar length

rbar,ε

rbar,PA


Structure and dynamics of the central regions of disk galaxies

Properties of Bars in the Nearby Universe

Bar strength

is the contribution of the bar to the total galaxy potential.

Whyte et al. 2002


Structure and dynamics of the central regions of disk galaxies

Properties of Bars in the Nearby Universe

1.Galaxy local environment

2. Galaxy central light concentration

3. Galaxy colors

Bars and Galaxy properties


Structure and dynamics of the central regions of disk galaxies

Properties of Bars in the Nearby Universe

We computed the number density of local galaxies using the distance d5 of the galaxy to its fifth nearest neighbor (Balogh et al. 2004). Thus the projected galaxy density could be defined as

Galaxy local environment

Only galaxies located in a velocity range of ±1000 Km s-1


Structure and dynamics of the central regions of disk galaxies

Properties of Bars in the Nearby Universe

Central light concentration


Structure and dynamics of the central regions of disk galaxies

Properties of Bars in the Nearby Universe

Galaxy colors


Structure and dynamics of the central regions of disk galaxies

Properties of Bars in the Nearby Universe

Conclusions

1. We found that 45% of disk galaxies are barred. The fraction of bars in the three morphological bins are 32%, 55%, and 52% for lenticulars, early and late-type spirals, respectively.

2. Bars of lenticular galaxies were found to be less frequent and weaker than those in spirals

3. No difference between the local galaxy density was found between barred and non-barred galaxies in our sample

4. The fraction of barred galaxies decrease toward more concentrated galaxies

5. Among late-type spiral galaxies bars are hosted by bluer galaxies


Structure and dynamics of the central regions of disk galaxies

Peanut Bulges in Face-on GalaxiesA new kinematic approachMéndez-Abreu, J., Corsini, E. M., Debattista, Victor P., De Rijcke, S., Aguerri, J. A. L., Pizzella, A., “Confirmation of a Kinematic Diagnostic for Face-On Box/Peanut-shaped Bulges”, 2008, ApJ, 679, 73

NO PEANUT

PEANUT

Peanuts studied only inedge-on galaxies

Is there a relation between B/P bulges and bars?

Debattista et al. 2005


Structure and dynamics of the central regions of disk galaxies

Peanut Bulges in Face-on GalaxiesA new kinematic approach

Sample selection

  • Barred galaxies NGC98 and NGC600

    bright, undisturbed, with low inclination and resolved bars.

  • Unbarred galaxy NGC1703control object.

Challenging observations

  • High S/N spectra to measure h4 moment of the LOSVD

  • High spectral resolution (Face-on disk galaxies)

  • Time allocated at VLT- FORS2


Structure and dynamics of the central regions of disk galaxies

Double minimum

Peanut Bulges in Face-on GalaxiesA new kinematic approach

Kinematic measurements

The stellar kinematics was measured from the galaxy absorption features present in the wavelength range centered on the Ca II triplet (λλ8498, 8542, 8662) using the Penalized Pixel Fitting method(Cappellari & Emsellem 2004).


Structure and dynamics of the central regions of disk galaxies

Peanut Bulges in Face-on GalaxiesA new kinematic approach

Conclusions

1. We have confirmed the kinematic method developed by Debattista et al. (2005) ;

2. We have identified for the first time a B/P-shaped bulge in a face-on disk galaxy ;

3. Peanuts are always related to bars but not all bars present a peanut structure ;

4. This study open a new window in the study of the relations between Peanut features and bars.


Structure and dynamics of the central regions of disk galaxies

Conclusions

The conclusions of this thesis can be summarized in three main points:

1) The typical scaling relations for galaxies cannot be used alone to distinguish between the different formation scenarios proposed until now since different models are able nowadays to reproduce these relations. However, measuring the intrinsic structural properties represents an useful step forward in this field and sets new constraints that should be reproduce by simulations.

2) The link between bulges and bars appears to be fundamental to understand the formation of both components.

3) The distinction between disk-like and boxy/peanut pseudo-bulges can be now investigated by a new kinematic diagnostic that can be applied in face-on galaxies. This result opens a new line of research which will help to give a more general scheme of bulge formation and evolution.


Structure and dynamics of the central regions of disk galaxies

THANKS !!!


Structure and dynamics of the central regions of disk galaxies

Properties of Bars in the Nearby Universe

Conclusions

1. We found that 45% of disk galaxies are barred. The fraction of bars in the three morphological bins are 32%, 55%, and 52% for lenticulars, early and late-type spirals, respectively.

2. Bars of lenticular galaxies were found to be weaker than those in spirals

3. No difference between the local galaxy density was found between barred and non-barred galaxies in our sample

4. The fraction of barred galaxies decrease toward more concentrated galaxies

5. Among late-type spiral galaxies bars are hosted by bluer galaxies


Structure and sp of bulges

Structure and SP of Bulges

Stellar kinematics

The stellar kinematics was measured from the Mg Triplet absoption lines by applying the Fourier Correlation Quotient method (Bender 1990).

Line-strength indices

The Mg, Fe and Hβ line-strength indices were measured.

To address the problem of emission lines we use GANDALF (Gas AND Absorption Line Fitting, Sarzi et al. 2006).

[MgFe]’=Mgb(0.72 x Fe5270 + 0.28 x Fe5335)

<Fe>=(Fe5270 + Fe5335)/2


Structure and sp of bulges1

Structure and SP of Bulges

Ages, metallicities and α/Fe ratios: Central values

From the central line-strength indices we derived the mean ages, total metallicities, and total α/Fe ratios by using the stellar populations models by Thomas et al. (2003).


Structure and sp of bulges2

Structure and SP of Bulges

Ages, metallicities and α/Fe ratios: Gradients

The gradient were set as the difference between the values at the galaxy center and rbd (the radius where the surface brightness of the bulge is equal to that of the disk)


Structure and sp of bulges3

Structure and SP of Bulges

Pseudobulges

Following the prescriptions given by Kormendy & Kennicutt (2005)

  • Apparent flattening of the bulge similar to that of the disk

  • Sérsic index n ≤ 2

  • Rotationally dominated in the v/σvsε diagram

  • Low sigma outlier in the FJ relation

NGC 1292 is the most reliable pseudobulge of our sample.

Age = 3Gyrs

[Z/H] = -0.7 dex

[α/Fe] = -0.12 dex


3d shape of bulges the intrinsic equatorial ellipticity

Abel-like integral equation

3D Shape of BulgesThe intrinsic equatorial ellipticity

Global Statistics


Structure and dynamics of the central regions of disk galaxies

Structure of disk galaxies

Bulge parameters

and correlations


Structure and dynamics of the central regions of disk galaxies

Conclusions

The aim of this thesis was to shed some light on the formation and evolution scenarios for the bulges in disk galaxies proposed until now: monolithic collapse, hierarchical merger, and secular evolution.

Throughout this thesis, we have presented a series of new results spanning the most important issues in extragalactic astronomy of individual galaxies, i.e., their structure, stellar populations, and kinematics.

The necessity, in the scientific community, for a new code to photometrically decompose galaxies with three components (bulge, disk, and bar) was our main concern when we started this thesis.

To fill this gap, we developed a new quantitative morphological analysis based on the new code GASP2D.

The power and utility of GASP2D has been proved throughout this thesis by using the code with different samples of nearby galaxies.


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