210 research outputs found
GHASP: an H kinematic survey of spiral galaxies - X. Surface photometry, decompositions and the Tully-Fisher relation in the Rc-band
We present Rc-band surface photometry for 170 of the 203 galaxies in GHASP,
Gassendi H-Alpha survey of SPirals, a sample of late-type galaxies for which
high-resolution Fabry-Perot H{\alpha} maps have previously been obtained. Our
data set is constructed by new Rc-band observations taken at the Observatoire
de Haute-Provence (OHP), supplemented with Sloan Digital Sky Survey (SDSS)
archival data, obtained with the purpose of deriving homogeneous photometric
profiles and parameters. Our results include Rc-band surface brightness
profiles for 170 galaxies and profiles for 108 of these objects. We
catalogue several parameters of general interest for further reference, such as
total magnitude, effective radius and isophotal parameters -- magnitude,
position angle, ellipticity and inclination. We also perform a structural
decomposition of the surface brightness profiles using a multi-component method
in order to separate disks from bulges and bars, and to observe the main
scaling relations involving luminosities, sizes and maximum velocities.
We determine the Rc-band Tully Fisher relation using maximum velocities
derived solely from H rotation curves for a sample of 80 galaxies,
resulting in a slope of , zero point of and an
estimated intrinsic scatter of . We note that, different from
the TF-relation in the near-infrared derived for the same sample, no change in
the slope of the relation is seen at the low-mass end (for galaxies with
km/s). We suggest that this different behaviour of the Tully
Fisher relation (with the optical relation being described by a single
power-law while the near-infrared by two) may be caused by differences in the
stellar mass to light ratio for galaxies with km/s.Comment: 17 pages, 11 figure
Integral field spectroscopy with SINFONI of VVDS galaxies. II. The mass-metallicity relation at 1.2 < z < 1.6
This work aims to provide a first insight into the mass-metallicity (MZ)
relation of star-forming galaxies at redshift z~1.4. To reach this goal, we
present a first set of nine VVDS galaxies observed with the NIR integral-field
spectrograph SINFONI on the VLT. Oxygen abundances are derived from empirical
indicators based on the ratio between strong nebular emission-lines (Halpha,
[NII]6584 and [SII]6717,6731). Stellar masses are deduced from SED fitting with
Charlot & Bruzual (2007) population synthesis models, and star formation rates
are derived from [OII]3727 and Halpha emission-line luminosities. We find a
typical shift of 0.2-0.4 dex towards lower metallicities for the z~1.4
galaxies, compared to the MZ-relation in the local universe as derived from
SDSS data. However, this small sample of eight galaxies does not show any clear
correlation between stellar mass and metallicity, unlike other larger samples
at different redshift (z~0, z~0.7, and z~2). Indeed, our galaxies lie just
under the relation at z~2 and show a small trend for more massive galaxies to
be more metallic (~0.1 logarithmic slope). There are two possible explanations
to account for these observations. First, the most massive galaxies present
higher specific star formation rates when compared to the global VVDS sample
which could explain the particularly low metallicity of these galaxies as
already shown in the SDSS sample. Second, inflow of metal-poor gas due to tidal
interactions could also explain the low metallicity of these galaxies as two of
these three galaxies show clear signatures of merging in their velocity fields.
Finally, we find that the metallicity of 4 galaxies is lower by ~0.2 to 0.4 dex
if we take into account the N/O abundance ratio in their metallicity estimate.Comment: 7 pages, 4 figures, accepted in A&A Comments: Comments: more accurate
results with better stellar mass estimate
High star formation rates as the origin of turbulence in early and modern disk galaxies
High spatial and spectral resolution observations of star formation and
kinematics in early galaxies have shown that two-thirds are massive rotating
disk galaxies with the remainder being less massive non-rotating objects. The
line of sight averaged velocity dispersions are typically five times higher
than in today's disk galaxies. This has suggested that
gravitationally-unstable, gas-rich disks in the early Universe are fuelled by
cold, dense accreting gas flowing along cosmic filaments and penetrating hot
galactic gas halos. However these accreting flows have not been observed, and
cosmic accretion cannot power the observed level of turbulence. Here we report
on a new sample of rare high-velocity-dispersion disk galaxies we have
discovered in the nearby Universe where cold accretion is unlikely to drive
their high star-formation rates. We find that the velocity dispersion is most
fundamentally correlated with their star-formation rates, and not their mass
nor gas fraction, which leads to a new picture where star formation itself is
the energetic driver of galaxy disk turbulence at all cosmic epochs.Comment: 9 pages, 2 figures, Supplimentary Info available at:
http://pulsar.swin.edu.au/~agreen/nature/sigma_mean_arXiv.pdf. Accepted for
publication in Natur
The Physics and Mass Assembly of distant galaxies with the E-ELT
One of the main science goal of the future European Extremely Large Telescope
will be to understand the mass assembly process in galaxies as a function of
cosmic time. To this aim, a multi-object, AO-assisted integral field
spectrograph will be required to map the physical and chemical properties of
very distant galaxies. In this paper, we examine the ability of such an
instrument to obtain spatially resolved spectroscopy of a large sample of
massive (0.1<Mstellar<5e11Mo) galaxies at 2<z<6, selected from future large
area optical-near IR surveys. We produced a set of about one thousand numerical
simulations of 3D observations using reasonable assumptions about the site,
telescope, and instrument, and about the physics of distant galaxies. These
data-cubes were analysed as real data to produce realistic kinematic
measurements of very distant galaxies. We then studied how sensible the
scientific goals are to the observational (i.e., site-, telescope-, and
instrument-related) and physical (i.e., galaxy-related) parameters. We
specifically investigated the impact of AO performance on the science goal. We
did not identify any breaking points with respect to the parameters (e.g., the
telescope diameter), with the exception of the telescope thermal background,
which strongly limits the performance in the highest (z>5) redshift bin. We
find that a survey of Ngal galaxies that fulfil the range of science goals can
be achieved with a ~90 nights program on the E-ELT, provided a multiplex
capability M Ngal/8.Comment: 21 pages, 13 figures, 7 tables. Accepted for publication in MNRA
Deep H{\alpha} Observations of NGC 253: a Very Extended and Possibly Declining Rotation Curve?
This study presents a deep H{\alpha} kinematical analysis of the Sculptor
Group galaxy NGC253. The Fabry-Perot data were taken with the 36-cm Marseille
Telescope in La Silla, Chile, using an EMCCD detector. Typical emission
measures of ~0.1 cm^-6 pc are reached. The observations allow the detection of
the Diffuse Ionized Gas component through [N II] emission at very large radii
of 11.5', 12.8' and 19.0', on the receding side of the galaxy. No H{\alpha}
emission is observed at radii larger than the neutral component (11.5'). The
very extended rotation curve confirms previous results and shows signs of a
significant decline, on the order of 30 per cent vmax . Using the rotation
data, mass models are constructed with and without the outer [N II] data
points, and similar results are found. The declining part of the rotation curve
is very well modeled, and seems to be truly declining.Comment: Accepted for publication in MNRAS. 16 pages, 10 figures, 4 table
MASSIV: Mass Assembly Survey with SINFONI in VVDS. IV. Fundamental relations of star-forming galaxies at 1<z< 1.6
How mass assembly occurs in galaxies and which process(es) contribute to this
activity are among the most highly debated questions in galaxy formation
theories. This has motivated our survey MASSIV of 0.9<z<1.9 star-forming
galaxies selected from the purely flux-limited VVDS redshift survey. For the
first time, we derive the relations between galaxy size, mass, and internal
velocity, and the baryonic Tully-Fisher relation, from a statistically
representative sample of star-forming galaxies. We find a dynamical mass that
agrees with those of rotating galaxies containing a gas fraction of ~20%,
perfectly consistent with the content derived using the Kennicutt-Schmidt
formulation and the expected evolution. Non-rotating galaxies have more compact
sizes for their stellar component, and are less massive than rotators, but do
not have statistically different sizes for their gas-component. We measure a
marginal evolution in the size-stellar mass and size-velocity relations in
which discs become evenly smaller with cosmic time at fixed stellar mass or
velocity, and are less massive at a given velocity than in the local Universe.
The scatter in the Tully-Fisher relation is smaller when we introduce the S05
index, which we interpret as evidence of an increase in the contribution to
galactic kinematics of turbulent motions with cosmic time. We report a
persistently large scatter for rotators in our relations, that we suggest is
intrinsic, and possibly caused by complex physical mechanism(s) at work in our
stellar mass/luminosity regime and redshift range. Our results consistently
point towards a mild, net evolution of these relations, comparable to those
predicted by cosmological simulations of disc formation for at least 8Gyr and a
dark halo strongly coupled with galactic spectrophotometric properties
The Tully-Fisher Relation for 25,000 SDSS Galaxies as Function of Environment
We construct Tully-Fisher relationships (TFRs) in the , , , and
bands and stellar mass TFRs (smTFRs) for a sample of late spiral
type galaxies (with ) from the Sloan Digital Sky Survey (SDSS)
and study the effects of environment on the relation. We use SDSS-measured
Balmer emission line widths, , as a proxy for disc circular
velocity, . A priori it is not clear whether we can construct
accurate TFRs given the small diameter of the fibres used for SDSS
spectroscopic measurements. However, we show by modelling the H
emission profile as observed through a aperture that for galaxies at
appropriate redshifts () the fibres sample enough of the disc to
obtain a linear relationship between and ,
allowing us to obtain a TFR and to investigate dependence on other variables.
We also develop a methodology for distinguishing between astrophysical and
sample bias in the fibre TFR trends. We observe the well-known steepening of
the TFR in redder bands in our sample. We divide the sample of galaxies into
four equal groups using projected neighbour density () quartiles and
find no significant dependence on environment, extending previous work to a
wider range of environments and a much larger sample. Having demonstrated that
we can construct SDSS-based TFRs is very useful for future applications because
of the large sample size available.Comment: accepted for publication in MNRAS. 15 pages, 12 figure
MASSIV: Mass Assembly Survey with SINFONI in VVDS. VI. Metallicity-related fundamental relations in star-forming galaxies at
The MASSIV (Mass Assembly Survey with SINFONI in VVDS) project aims at
finding constraints on the different processes involved in galaxy evolution.
This study proposes to improve the understanding of the galaxy mass assembly
through chemical evolution using the metallicity as a tracer of the star
formation and interaction history. Methods. We analyse the full sample of
MASSIV galaxies for which a metallicity estimate has been possible, that is 48
star-forming galaxies at , and compute the integrated values of
some fundamental parameters, such as the stellar mass, the metallicity and the
star formation rate (SFR). The sample of star-forming galaxies at similar
redshift from zCOSMOS (P\'erez-Montero et al. 2013) is also combined with the
MASSIV sample. We study the cosmic evolution of the mass-metallicty relation
(MZR) together with the effect of close environment and galaxy kinematics on
this relation. We then focus on the so-called fundamental metallicity relation
(FMR) proposed by Mannucci et al. (2010) and other relations between stellar
mass, SFR and metallicity as studied by Lara-L\'opez et al. (2010). We
investigate if these relations are really fundamental, i.e. if they do not
evolve with redshift. Results. The MASSIV galaxies follow the expected
mass-metallicity relation for their median redshift. We find however a
significant difference between isolated and interacting galaxies as found for
local galaxies: interacting galaxies tend to have a lower metallicity. The
study of the relation between stellar mass, SFR and metallicity gives such
large scattering for our sample, even combined with zCOSMOS, that it is
diffcult to confirm or deny the existence of a fundamental relation
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