BULGES NGC 4710 NGC 4594 ESO 498-G5 NGC 4565 NGC 7457 ESO 1129 - - PowerPoint PPT Presentation

BULGES

NGC 7457 ESO 498-G5 NGC 4710 ESO 1129 NGC 4565 NGC 4594

FORMATION AND EVOLUTION OF BULGES

Classical bulge Pseudobulge Boxy/peanuts bulge

• Presents in early type galaxies: lenticular, Sa
• Very similar to elliptical : Mg2 -  ; Dn - ; FP; SSP, R(1/4)
• Some differences: fotometry shows young stellar populations
• Formation trough dissipative collapse or merger events (theoretical)
• Presents in late type galaxies: Sb and later type
• Luminosity profile is exponential
• They are flat component, with a disk kinematic
• Star formation
• Formed trough secular evolution slow rearrangement of disk material

indicate no major merger (theoretical)

• boxy/peanut bulges are parts of bars seen edge-on, have their origin in

vertical instabilities of the disc and are somewhat shorter in extent than bars.

• Their stellar population is similar to that of the inner part of the disc from

which they formed.

FORMATION AND EVOLUTION OF BULGES

Boxy/Peanut Bulges Disk-like Bulges Classical Bulges

Eggen et al. 1962 Sandage 1990 Gilmore & Wyse 1998 Kauffmann 1996 Baugh et al. 1996 Cole et al. 2000 Raha et al. 1991 Debattista et al. 2004 Martínez-Valpuesta et al. 2006 Aguerri et al. 2001 Fu et al. 2003 Eliche-Moral et al. 2006 Athanassoula 1992 Heller & Shlosman 1994 Shen & Sellwood 2004

Dissipative collapse

• Presence of metallicity and

α/Fe gradient (Kobayashi 2004).

• Presence of metallicity

gradient with flat profile of α/Fe (Pipino et al. 2008).

Merging events Secular evolution

IN THE CURRENT PARADIGM…

• Absent (or very shallow)

gradients in bulges (Bekki & Shioya 1999)

• metallicity gradient rarely

enhanced by secondary events of star formation (Hopkins et al. 2009). Classical Bulges Disk-like Bulges

Different formation mechanism leave differences in the stellar populations and in their radial profiles

• Gradients eventualy present could

either be amplified (change of scalelength) or erased (disc heating) (Moorthy & Holtzman 2006)

Which is the relative importance of different mecchanism (is one dominant?)

Model predictions…

• More constraints from comparison
• f stellar populations of disk and

bulge

FORMATION AND EVOLUTION OF BULGES

STELLAR POPULATION RELATED WITH THE ENVIRONMENT WHERE THE GALAXY FORM AND EVOLVE

• CLUSTER
• FIELD

Potential wheel formation stop the merging in cluster (Z >2) Merging continue (Z < 1) FIELD GALAXIES YOUNGER THAN CLUSTER COUNTERPART OBSERVATION (elliptical and early type): EXTENDED DATA FIELD YOUNGER AND HIGHER METALLICITY CENTRAL VALUES NO DIFFERENCES BETWEEN CLUSTER AND FIELD GROUP

De la rosa et al. 2001 , Collobert et al 2006 Bernardi et al. 1998 Bought et al 1996

ENVIRONMENT

Central values and gradients Environment Late type

GALAXIES SAMPLE SELECTION

14 BRIGHT, NEARBY, CLUSTER, GALAXIES

OBSERVATION AND DATA REDUCTION

STANDARD REDUCTION FOR LOW RESOLUTION DATA AQUIRED WITH EFOSC2@3.6ESO

KINEMATIC AND LINESTRENGTH ANALYSIS

1) ROTATION GALAXY VELOCITY AND ROTATION VELOCITY DISPERSION MEASURED 2) LINE STRENGTH OF LICK INDICES MEASUERED USING WORTHEY ET AL. 1994 DEFINITION

PHOTOMETRIC ANALYSIS

2D PHOTOMETRIC DECOMPOSITION TO DISENTAGNGLE BULGE FROM DISK

RESULTS…… …STEP BY STEP……

Consistency of results Comparison with the lick system.. Comparison with litterature

MAJOR AXIS KINEMATICS AND LINE-STRENGTH

Rbd Rbd Rbd

Disc dominated region

Nuclear region Bulge dominated region

ANALISYS OF THE STELLAR POPULATIONS

…RESULTS……

• AGE METALLICITY AND /ENHANCEMENT
• AGE METALLICITY and /ENHANCEMENT

CENTRAL VALUES RADIAL PROFILES PSEUDOBULGES

• NGC 1292

CONCLUSIONS

LINE STRENGTH PROFILES LINE STRENGTH CENTRAL VALUES 1) Most of the sample galaxies show no gradient in age (merging events ) but a negative gradient of metallicity. (dissipative collapse) 2) no gradient was measured in the [α/Fe] radial profiles for all the galaxies (No inside-out scenario expected from merging) 1) The value of /<Fe> is for most of the galaxies between solar and 0.3 ( This imply time-scale that can be very short for star formation) 2) More massive bulges are older, more metal rich and characterized by a fast star formation.

• Star formation fast and homogeneus in the bulge

CENTRAL VALUES: H, Mg2, <Fe>-

IN LATER TYPE ? STRUCTURAL PROPERTIES CORRELATE CHEMICAL PROPERTIES 

Mg2, H, Fe

IN ELLIPTICAL GALAXIES

We found good correlation for <Fe> Mg2, H still correlate Hint they are steeper…

AGE AND METALLICITY CENTRAL VALUES

Model grids from Thomas et al. 2003

3 Gyr 12 Gyr

AGE AND METALLICITY CENTRAL VALUES

• Hint that early type are older and

metal richer than later type

Model grids from Thomas et al. 2003

T ≤ 0 T > 0

Very young Young Old

3 Gyr 12 Gyr

AGE AND METALLICITY CENTRAL VALUES

• No relation found with

morphological type

• No relation found with the

membership

Model grids from Thomas et al. 2003

Fornax Pegasus NGC 7582

3 Gyr 12 Gyr

• Most of objects show solar value of

/Fe while few have super solar /Fe

AGE AND METALLICITY CENTRAL VALUES

• No relation found with

morphological type

• No relation found with the

membership

• 3 clear different classes of ages
• Relation age-metallicity

Very young Young Old

• Important correlation with the central

velocity rotation dispersion

• More massive bulges are older, more

metal rich

AGE AND METALLICITY RADIAL PROFILES

• Metallicity is

decreasing with the radius

• Age shows no

gradient

Grad[Z/H] = [Z/H] (center)- [Z/H] (1Rbd) (Mehlert et al. 2003) Grad(Age) = Age (center)-Age (1Rbd) (Mehlert et al. 2003)

Collapse model produce metallicity gradient

Early-type Mehlert et al. 2003 Bulges Jabloka et al. 2007

AGE AND METALLICITY RADIAL PROFILES

• No gradient found

with the radius

• Solar to super-solar value

(result from central value)

Grad( /<Fe>) = /<Fe> (center)-/<Fe> (Rbd) (Mehlert et al. 2003)

Merger model do not produce gradient and produce solar /<Fe> Collapse model produce /<Fe> gradient

THE GALAXIES SAMPLE

• 14 CLUSTER GALAXIES ( Ferguson 1989; Garcia 1983)
• BRIGHT (BT < 15.5 Mag)
• NEARBY GALAXIES (cz<4500 km s-1)
• MORPHOLOGICAL TYPE: SPIRAL GALAXIES

Fornax, Eridanus, Pegasus, N7582

SPECTROSCOPIC OBSERVATIONS

• 2 RUNS AT EFOSC@ESO3.6 TELESCOPE
• WAVELENGTH RANGE = 4700-6700 Å
• DISPERSION = 1.98 Å/PIXEL
• INSTRUMENTAL FWHM  6 Å
• SPATIAL RESOLUTION = 0.314 ARCSEC

Calibration and Observation

• BASIC CALIBRATION (bias, flat, HeAr calibration lamp)
• SPECTRA TAKEN ALONG THE MAJOR AXIS
• TYPICAL EXPOSURE TIME 2x3600 s S/N>35-40
• 2-5 LICK/VELOCITY STANDARD STARS (G, K spectral type)

KINEMATICS AND LINESTRENGTH

• KINEMATICAL MEASUREMENTS
• LINE STRENGTH MEASUREMENTS

Worthey et al.1994



    d

F F EW

C I



         

2 1

1

Atomic indices

                             



  

    d

F F EW

C I

2 1

1 1 log 5 . 2

2 1

Molecular indices

We measured the profiles along the major axis of the values of the rotation velocity (v), rotation velocity dispersion () We measured the values of the indices defined in the LICK/IDS system for all the those present in our range

They are => H, Fe5015, Mg1, Mg2, Mgb, Fe5270,Fe, 5335, NaD

LICK INDICES OVERVIEW

Lick indices related with age metallicity and /Fe

Possible way to break the degeneracy…

(Whortey et al. 1994, Thomas et al.2003)

5335 28 . 5270 72 . ( Fe Fe Mg MgFe

b

   

• Balmer lines (H, H …)

Stellar population age

• The iron and magnesium lines

Metallicity

• Mg/<Fe> or /<Fe>

Timescale of the star formation

PSEUDOBULGES - THE CASE OF NGC 1292

CLASSICAL BULGES PSEUDO-BULGES

• Flattened disk like structures, may

have secondary bars, rings, and/or spiral structure

• Dynamically cold – rotation

dominated

• Formed from slow rearrangement of

disk material – indicate no major merger

• Usually in types Sbc and later
• In globally blue galaxies
• resemble little ellipticals

whic happen to have a disc

• dynamically hot -

dispersion dominated

• formed via violent

relaxation during major merger

• in types S0-Sbc
• in globally red galaxies

Kormendy and Kennicut 2004 translate these general concepts in a list cookbook rules

(The more apply, the safer the classification becomes)

Secular evolution Merging/dissipative collapse

PSEUDOBULGES - THE CASE OF NGC 1292

APPLICATION OF KORMENDY RULES TO OUR SAMPLE

S´ersic index (n < 2) Most of the sample bulges have it (9/14) Ellipticity compared with Vmax/σ0 The apparent flattening of the bulge is similar to that of the disc

NGC 1292, NGC 1351

NGC 1292 satisfy all the conditions

pseudobulge

Outsider in the FJ relation

Forbes & Ponman (1999)

PSEUDOBUGES

PSEUDOBULGES - THE CASE OF NGC 1292

STELLAR POPULATION

• YOUNG AGE (T=3 Gyr)
• LOW METAL CONTENTS ([Z/H] =-0.7)
• OVERABUNDANCE [/Fe]=-0.12

CENTRAL REGIONS ARE:

Radius

DATING THE FORMATION OF THE COUNTER-ROTATING STELLAR DISC IN THE SPIRAL GALAXY NGC 5719 BY DISENTANGLING ITS STELLAR POPULATIONS COUNTER-ROTATIONS

presence of stars/gas counter-rotating with respect to other stars and/or gas NGC 7217

FEW GAS LOT OF GAS

• external origin gas disk built by retrograde acquisitions
• internal origin Gas disk built by a bar

Subsequent star formation in the acquired gas disk

FORMATION OF GAS COUNTER-ROTATIONS 1) Acquisition of gas

• external origin merger with other galaxies
• internal origin secular evolution with disk instability

2) Acquisition of already formed stars and gas

NGC 2855

FORMATION OF GAS COUNTER-ROTATIONS

• external origin gas disk built by retrograde acquisitions
• internal origin Gas disk built by a bar

Subsequent star formation in the acquired gas disk

FORMATION OF GAS COUNTER-ROTATIONS 1) Acquisition of gas

• external origin merger with other galaxies
• internal origin secular evolution with disk instability

2) Acquisition of already formed stars and gas Expected observables

1)

Age of the counter-rotating component is younger

2)

Age of the counter rotating component younger in the 50% of case Metallicity of gas and stars possibly different

NGC 5719 – DISENTANGLING THE SPECTRA

Flux wavelength

NGC 5719

TEST CASE… gas count-stars co-stars

NGC 5719 – OBSERVATIONS

VIMOS - VIsible MultiObject Spectrograph @UT3

• The integral-field spectroscopic observations in service mode
• We used the 0.67 arcsec per fiber resolution
• Spectral range 4150–6200 Å with a reciprocal dispersion of 0.54

Å/pixel

• The instrumental spectral resolution measured at 5200 Å was 2.0 Å

(FWHM)

NGC 5719 – DISENTANGLING THE SPECTRA

NGC 5719 – 2D FIELD kinematic

gas count-stars co-stars

NGC 5719 – INDICES

NGC 5719 – 2D FIELD STELLAR POPULATION

Age

Metallicity A/Fe

Corotating Counter-Corotating

NGC 5719 – CONCLUSIONS

• 5719 is decomposed into the contributions of three distinct kinematic

components characterised by a regular disc-like rotation: one main and one secondary stellar component and a ionised-gas component.

• The ionised gas is detected all over the observed field of view. It is

characterised by a strong Hβ emission, which is concentrated in a twin-peaked morphology indicating an edge-on ring

• The contributions of the 2 components to the total light is F(main) = 56% and

F(secondary) = 44%

• We prove that the mean age of the counter-rotating disc, which is associated to

the neutral and ionised gas disc, is indeed younger than the main stellar disc. This result shows that counter-rotating disc has been recently assembled.

• The scenario proposed by Vergani et al. (2007) that NGC 5719 hosts a

counter-rotating stellar disc originated from the gas accreted during the

• ngoing merging with its companion NGC 5713, is finally confirmed.

NGC 4550

NGC 3593

NGC 4550, NGC 3593 – STELLAR POPULATIONS

NGC 5719, NGC 3593, NGC 4550 – CONCLUSIONS

• NGC 3593 and NGC 4550 host a counter-rotating stellar disk, which rotates in the

same direction as the ionized gas, and which is on average less massive, younger, metal poorer, and more α enhanced than the main stellar galaxy disk.

• NGC 3593: counter rotating stellar disk is younger than the main disk
• NGC 4550: counter rotating stellar disk is younger than the main disk
• Our results support the scenario of external gas acquisition, followed by a subsequent
• utside-in star formation as the origin of the observed counter-rotation.
• The merger scenario cannot be completely ruled out, given the low statistics available.

Counterotation – next step

Large survey of the north and south sky to oberve all the galaxy with hints of counter

• rotations. Candidates for the north are chosen with Afosc@1.8 Asiago telescope.

SOUTH NORTH VIMOS@VLT VIRUS-P@VLT