Morphology, Kinematics and Star Formation Across the Hubble Sequence of Galaxies

207 Pages·2016·13.65 MB·English

by  Santiago Erroz-Ferrer (auth.)

Springer Theses
Recognizing Outstanding Ph.D. Research
Santiago Erroz-Ferrer

Morphology,
Kinematics and Star
Formation Across the
Hubble Sequence
of Galaxies
Springer Theses
Recognizing Outstanding Ph.D. Research
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Santiago Erroz-Ferrer
Morphology, Kinematics
and Star Formation Across
the Hubble Sequence
of Galaxies
Doctoral Thesis accepted by
the University of La Laguna, Spain
123
Author Supervisor
Dr. SantiagoErroz-Ferrer Prof. JohanKnapen
Instituto deAstrofísicadeCanarias Instituto deAstrofísicadeCanarias
University of LaLaguna University of LaLaguna
SanCristóbal deLa Laguna SanCristóbal deLa Laguna
Spain Spain
and
CaseWestern ReserveUniversity
Cleveland, OH
USA
ISSN 2190-5053 ISSN 2190-5061 (electronic)
SpringerTheses
ISBN978-3-319-26397-7 ISBN978-3-319-26398-4 (eBook)
DOI 10.1007/978-3-319-26398-4
LibraryofCongressControlNumber:2015954963
SpringerChamHeidelbergNewYorkDordrechtLondon
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’
Supervisor s Foreword
Galaxies are the building blocks of the Universe, and the study of their formation
and evolution is key to the understanding of how the Universe has acquired its
presentshape. Ofparticularinterest isthedetailedstudy oftheinternal,or secular,
evolution of galaxies. This describes the evolution induced by internal processes
suchastheactionsofspiralarms,bars,ovals,galacticwinds,blackholes,anddark
matter haloes. Secular evolution plays an important role in the evolution of spiral
galaxies,and one key advantageis that one can study therelevant physics ingreat
detail through observations of the nearest galaxies.
This thesis describes a study of the morphology, kinematics, and star formation
properties of carefully selected samples of nearby galaxies. The work is closely
related to the Spitzer Survey of Stellar Structure of Galaxies (S4G), a mid-infrared
imaging study of some 3000 nearby galaxies. This Survey has provided accurate
measurements of many basic parameters of the sample galaxies, such as morpho-
logical type, stellar mass, and the presence of structural components such as bars,
lenses, or rings. In the context of this thesis, a subsample of 29 galaxies was
selected from the overall sample for follow-up study, and observed with two dif-
ferent instruments on the 4.2 m William Herschel Telescope in La Palma: ACAM
and GHαFAS. With those, imaging in the Hα line and Fabry-Perot spectroscopy
was obtained, to derive star formation rates and gas kinematics, respectively.
Among the main results of the thesis is the study of correlations of kinematic
parameters of the sample galaxies, such as the central slope of the rotation curve,
with the overall parameters of the galaxies and their spiral arms and bars.
A fundamental advance here is that a sample of 29 galaxies was used, spanning a
wide range in morphological type, stellar mass, and bar and spiral properties, and
that kinematic data at high spatial and spectral resolution were obtained for all
of them. In combination with the accurate parameters yielded by the S4G survey,
important results are obtained on streaming and other non-circular motions in
galaxies, on the distribution and rates of star formation, and on how correlations
of these parameters and of the rotation curve shape with basic galaxy parameters
yield clues on the evolutionary processes taking place in disk galaxies. The data
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vi Supervisor’sForeword
obtained for this project have all been made public, and form part of the lasting
legacy of this work.
This thesis work, carried out between September 2010 and October 2014 at the
University of La Laguna and the Instituto de Astrofísica de Canarias, has led to a
number of publications in refereed journals and presentations at international
conferences. The thesis was defensed at the Aula Magna of the Physics Faculty
of the University of La Laguna (Tenerife, Spain), and was honoured Summa Cum
Laude.
San Cristóbal de La Laguna Prof. Johan Knapen
July 2015
Preface
The topic of this thesis is the study of the morphology, kinematics, and star for-
mation of nearby galaxies, aiming to clarify a number of long-standing open
questions about their formation, evolution, and physical properties.
First, I have addressed the star formation and its distribution across the Hubble
sequence of galaxies. In particular, I have studied massive star formation in ellip-
tical, lenticular, and early-type galaxies. Although these galaxies have generally
low gas content and low levels of star formation, there is a significant subset that
shows evidence of ongoing star formation in the form of extended UV emission.
I have obtained Hα imaging of ten such galaxies, finding that in most cases, their
starformationratesarecomparabletothosefoundindiskgalaxies.Thisisprobably
because the sample selection is biased toward star-forming galaxies. I confirm that
massivestarformationcausestheextendedUVemissioninoursample,intheform
of outer spiral arms and/or outer (pseudo) rings.
This thesis has been developed in the context of the Spitzer Survey of Stellar
StructureinGalaxies(S4G),whichhasobtainedmid-IRimagesofmorethan2350
galaxies in the local Universe. These images and the studies within the S4G col-
laboration have been complemented with the ancillary kinematic data obtained
within the framework of this thesis. I present a kinematical study of 29 spiral
galaxiesincludedintheS4Gsample,usingHαFabry-Perot(FP)dataobtainedwith
theGalaxyHαFabry-PerotSysteminstrumentattheWilliamHerschelTelescopein
LaPalma,complementedwithimagesintheRbandandinHα.Theprimarygoalis
tostudytheevolutionandpropertiesofthemainstructuralcomponentsofgalaxies
through the kinematical analysis of the FP data, complemented with studies of
morphology, star formation, and mass distribution. In this thesis, I describe how
these data have been obtained, processed, and analyzed. This program of 3D
kinematicsenables thestudy of themotions oftheionized gaswithinthe galaxies,
including in-depth investigations of the rotation curves, velocity moment maps,
velocity residual maps, and position–velocity diagrams.
Galaxy disks are supported by rotation to minimize the total energy when
conserving the angular momentum. However, through the evolution of a galaxy,
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viii Preface
several processes interfere on the kinematics of the galaxy and provoke deviations
from the pure rotation, what we call non-circular motions. In particular,
non-axisymmetric structures such as bars are understood to create potentials that
influence the way material move toward the center of the galaxy. As a first step to
understandthenon-circularmotions,Ipresentdetailedresultsonthebarredgalaxy
NGC864fromthekinematicalprogram.Ifindasymmetriesinthevelocityfieldin
thebarzone,causedbynon-circularmotions,probablyinresponsetothepotential
of the bar.
Thestudyregardingthenon-circularmotionsisexpandedtothewholesampleof
galaxies.Inparticular,thosemotionsfoundalongthebarsandspiralarms.Thedata
indicatethattheamplitudeofthenon-circularmotionscreatedbythebarintheHα
gas does not correlate with the strength of the bar. The amplitude of those non-
circularmotionsrelatedtothespiralarmsdoesnotcorrelatewitheitherarmclassor
star formation rate along the spiral arms. This implies that the presence and mag-
nitude of streaming motions in the arms seem to be a local phenomenon. I also
study here the global SFRs of the galaxies of the sample, and in particular the star
formation within the bar and its relationship with its kinematics.
The dynamics in the central parts of galaxies are influenced by both baryonic
matter(gasandstars)andDM.Thisthesiswilltrytofindoutwhichcontributionis
more important regarding the dynamics of the central parts of the galaxy. Taking
advantage of the high angular and spectral resolution of the kinematic data,
I perform a detailed study of the shape of the innermost part of the rotation curve
of the sample galaxies. In particular, I quantify the steepness of the rotation curve
bymeasuringitsslope.Aspreviouslynotedintheliteratureand,infact,physically
intuitive, I find that the compactness of the mass in the central parts of a galaxy
(more concretely, the presence of the bulge) is translated into steeper slopes.
Otherwise,Ifindnoinfluenceofthedegreeofsecularevolutionofagalaxyonthe
value of the slope, as the presence of the bar and the star formation rate does not
correlate with the slope. I find that although the luminous matter dominates the
gravitationalpotentialinthecentralpartsofthegalaxies,darkmatterisalsopresent.
Acknowledgments
IwouldliketothankJohanKnapen,RyanLeaman, MauricioCisternas,andBarry
Madore for his comments and suggestions during the preparation of this thesis.
I would like to thank Inma Martínez Valpuesta for her suggestions as the referee
ofthethesis.IwouldliketothankJoanFontandJoséRamónSánchez-Gallegofor
their assistance with the reduction and calibration of the FP and Hα data. I would
like to thank the Carnegie Observatories for hospitality and facility support.
The thesis is based on observations made with the NOT and WHT operated on
the island of La Palma, in the Spanish Observatorio del Roque de Los Muchachos
oftheInstitutodeAstrofísicadeCanarias.Thedatapresentedherewereobtainedin
partwithALFOSC,whichisprovidedbytheInstitutodeAstrofísicadeAndalucia
under a joint agreement with the University of Copenhagen and NOTSA.
Some of the data presented in this paper were obtained from the Mikulski
Archive for Space Telescopes (MAST). STScI is operated by the Association of
Universities for Research in Astronomy, Inc., under NASA contract NAS5-26555.
Support for MAST for non-HST data is provided by the NASA Office of Space
Science via grant NNX09AF08G and by other grants and contracts. I thank the
entire S4G team for their efforts in this project. This research has made use of the
HyperLeda database (http://leda.univ-lyon1.fr) and the NASA/IPAC Extragalactic
Database (NED), which is operated by JPL, Caltech, under contract with NASA.
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