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

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

FORMATION AND EVOLUTION OF BULGES Classical 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)  Pseudobulge 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/peanuts bulge 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 Eggen et al. 1962 Kauffmann 1996 Sandage 1990 Baugh et al. 1996 Gilmore & Wyse 1998 Cole et al. 2000 Classical Bulges Aguerri et al. 2001 Disk-like Bulges Fu et al. 2003 Athanassoula 1992 Eliche-Moral et al. 2006 Heller & Shlosman 1994 Shen & Sellwood 2004 Boxy/Peanut Bulges Raha et al. 1991 Debattista et al. 2004 Martínez-Valpuesta et al. 2006

FORMATION AND EVOLUTION OF BULGES IN THE CURRENT PARADIGM … Dissipative collapse Merging events Secular evolution Disk-like Bulges Classical Bulges Which is the relative importance of different mecchanism (is one dominant?) Different formation mechanism leave differences in the stellar populations and in their radial profiles Model predictions … Gradients eventualy present could Absent (or very shallow)   Presence of metallicity and  either be amplified (change of gradients in bulges (Bekki α/ Fe gradient (Kobayashi scalelength) or erased (disc heating) & Shioya 1999) 2004). (Moorthy & Holtzman 2006) metallicity gradient rarely  Presence of metallicity  enhanced by secondary gradient with flat profile of More constraints from comparison  events of star formation α/Fe (Pipino et al. 2008). of stellar populations of disk and (Hopkins et al. 2009). bulge

ENVIRONMENT STELLAR POPULATION RELATED WITH THE ENVIRONMENT WHERE THE GALAXY FORM AND EVOLVE  CLUSTER Potential wheel formation stop the merging in cluster (Z >2) Bought et al 1996  FIELD Merging continue (Z < 1) FIELD GALAXIES YOUNGER THAN CLUSTER COUNTERPART OBSERVATION (elliptical and early type): EXTENDED DATA FIELD YOUNGER AND HIGHER METALLICITY De la rosa et al. 2001 , Collobert et al 2006 CENTRAL VALUES NO DIFFERENCES BETWEEN CLUSTER AND FIELD GROUP Bernardi et al. 1998

Central values and Environment Late type gradients

…STEP BY STEP…… GALAXIES SAMPLE SELECTION 14 BRIGHT, NEARBY, CLUSTER, GALAXIES OBSERVATION AND DATA REDUCTION STANDARD REDUCTION FOR LOW RESOLUTION DATA AQUIRED WITH EFOSC2@3.6ESO PHOTOMETRIC ANALYSIS 2D PHOTOMETRIC DECOMPOSITION TO DISENTAGNGLE BULGE FROM DISK 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 RESULTS……

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

MAJOR AXIS KINEMATICS AND LINE-STRENGTH R bd R bd R bd

Nuclear region Bulge dominated region ANALISYS OF THE STELLAR POPULATIONS Disc dominated region

…RESULTS…… CENTRAL VALUES  AGE METALLICITY AND  /ENHANCEMENT RADIAL PROFILES  AGE METALLICITY and  /ENHANCEMENT PSEUDOBULGES  NGC 1292

CONCLUSIONS LINE STRENGTH CENTRAL VALUES 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. LINE STRENGTH PROFILES 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)  Star formation fast and homogeneus in the bulge

CENTRAL VALUES: H  , Mg 2, <Fe>-  IN ELLIPTICAL GALAXIES  STRUCTURAL PROPERTIES CORRELATE CHEMICAL PROPERTIES Mg 2 , H  , Fe IN LATER TYPE ? We found good Mg 2 , H  still correlate correlation for <Fe> Hint they are steeper…

AGE AND METALLICITY CENTRAL VALUES 3 Gyr 12 Gyr Model grids from Thomas et al. 2003

AGE AND METALLICITY CENTRAL VALUES  Hint that early type are older and metal richer than later type Very young Young Old 3 Gyr 12 Gyr T ≤ 0 Model grids from Thomas et al. 2003 T > 0

AGE AND METALLICITY CENTRAL VALUES  No relation found with Fornax morphological type Pegasus NGC 7582  No relation found with the membership 3 Gyr 12 Gyr Model grids from Thomas et al. 2003

AGE AND METALLICITY CENTRAL VALUES  No relation found with morphological type Young  No relation found with the membership Very  3 clear different classes of ages young  Relation age-metallicity  Most of objects show solar value of  /Fe while few have super solar  /Fe 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 Bulges Jabloka et al. 2007 Early-type Mehlert et al. 2003 the radius  Age shows no gradient Grad[Z/H] = [Z/H] (center)- [Z/H] (1R bd ) (Mehlert et al. 2003) Grad(Age) = Age (center)-Age (1R bd ) (Mehlert et al. 2003) Collapse model produce metallicity gradient

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> (R bd ) (Mehlert et al. 2003) Merger model do not produce gradient and produce solar  /<Fe> Collapse model produce  /<Fe> gradient

THE GALAXIES SAMPLE  BRIGHT (B T < 15.5 Mag)  NEARBY GALAXIES (cz<4500 km s -1 )  MORPHOLOGICAL TYPE: SPIRAL GALAXIES  14 CLUSTER GALAXIES ( Ferguson 1989; Garcia 1983) 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 We measured the profiles along the major axis of the values of the rotation velocity (v), rotation velocity dispersion (  )  LINE STRENGTH MEASUREMENTS 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, Mg 1 , Mg 2 , Mg b , Fe5270,Fe, 5335, NaD Worthey et al.1994 Molecular indices Atomic indices        2      F    d  1 2 F        d  I        EW 1   I EW 2 . 5 log 1          F       F       C 1 2 C 1 1

LICK INDICES OVERVIEW Lick indices related with age metallicity and  /Fe  Balmer lines ( H  , H  …) Stellar population age  The iron and magnesium lines Metallicity  Mg/<Fe> or  /<Fe> Timescale of the star formation Possible way to break the degeneracy…     MgFe Mg ( 0 . 72 Fe 5270 0 . 28 Fe 5335 b (Whortey et al. 1994, Thomas et al.2003)

PSEUDOBULGES - THE CASE OF NGC 1292 PSEUDO-BULGES CLASSICAL BULGES Merging/dissipative collapse  Flattened disk like structures, may  resemble little ellipticals have secondary bars, rings, and/or whic happen to have a Secular evolution spiral structure disc  Dynamically cold – rotation  dynamically hot - dominated dispersion dominated  Formed from slow rearrangement of  formed via violent disk material – indicate no major relaxation during major merger merger  Usually in types Sbc and later  in types S0-Sbc  In globally blue galaxies  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)

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/ σ 0 The apparent flattening of the bulge is PSEUDOBUGES similar to that of the disc NGC 1292, NGC 1351 Outsider in the FJ relation NGC 1292 satisfy all the conditions pseudobulge Forbes & Ponman (1999)

PSEUDOBULGES - THE CASE OF NGC 1292 STELLAR POPULATION Radius CENTRAL REGIONS ARE:  YOUNG AGE (T=3 Gyr)  LOW METAL CONTENTS ([Z/H] =-0.7)  OVERABUNDANCE [  /Fe]=-0.12