374 research outputs found
MaNGA: Mapping Nearby Galaxies at Apache Point Observatory
MaNGA (Mapping Nearby Galaxies at APO) is a galaxy integral-field
spectroscopic survey within the fourth generation Sloan Digital Sky Survey
(SDSS-IV). It will be mapping the composition and kinematics of gas and stars
in 10,000 nearby galaxies, using 17 differently sized fiber bundles. MaNGA's
goal is to provide new insights in galaxy formation and evolution, and to
deliver a local benchmark for current and future high-redshift studies.Comment: 7 pages, 3 figures. To appear in the proceedings of the conference
"Multi-Object Spectroscopy in the Next Decade: Big Questions, Large Surveys
and Wide Fields", held in Santa Cruz de La Palma, Canary Islands from 2nd to
6th March 2015. Eds. I. Skillen and S. Trage
[OIII] Emission and Gas Kinematics in a Lyman-alpha Blob at z ~ 3.1
We present spectroscopic measurements of the [OIII] emission line from two
subregions of strong Lyman-alpha emission in a radio-quiet Lyman-alpha blob
(LAB). The blob under study is LAB1 (Steidel et al. 2000) at z ~ 3.1, and the
[OIII] detections are from the two Lyman break galaxies embedded in the blob
halo. The [OIII] measurements were made with LUCIFER on the 8.4m Large
Binocular Telescope and NIRSPEC on 10m Keck Telescope. Comparing the redshift
of the [OIII] measurements to Lyman-alpha redshifts from SAURON (Weijmans et
al. 2010) allows us to take a step towards understanding the kinematics of the
gas in the blob. Using both LUCIFER and NIRSPEC we find velocity offsets
between the [OIII] and Lyman-alpha redshifts that are modestly negative or
consistent with 0 km/s in both subregions studied (ranging from -72 +/- 42 --
+6 +/- 33 km/s). A negative offset means Lyman-alpha is blueshifted with
respect to [OIII], a positive offset then implies Lyman-alpha is redshifted
with respect to [OIII]. These results may imply that outflows are not primarily
responsible for Lyman alpha escape in this LAB, since outflows are generally
expected to produce a positive velocity offset (McLinden et al. 2011). In
addition, we present an [OIII] line flux upper limit on a third region of LAB1,
a region that is unassociated with any underlying galaxy. We find that the
[OIII] upper limit from the galaxy-unassociated region of the blob is at least
1.4 -- 2.5 times fainter than the [OIII] flux from one of the LBG-associated
regions and has an [OIII] to Lyman-alpha ratio measured at least 1.9 -- 3.4
times smaller than the same ratio measured from one of the LBGs.Comment: submitted to Ap
The structure of dark and luminous matter in early-type galaxies
In this thesis we explore new techniques to study the dark and luminous matter in the outskirts of galaxies. To determine the mass and shape of the dark matter halo around the early-type galaxy NGC 2974, we measure the kinematics of its large neutral gas ring. We combine these large-scale kinematics with the central kinematics of the ionised gas to construct mass models of this galaxy. For galaxies that do not contain neutral gas, we use integral-field spectroscopy to measure the stellar kinematics at large radii. Briefly, we use the spectrograph as a "photon-collector", to obtain spectra with sufficient signal-to-noise. The kinematics are used to model the dark haloes around the galaxies NGC 2549, NGC 3379 and NGC 821. We also measure the line strengths from the spectra to determine the properties of the stellar population in the outer parts of these systems. Finally, we take a look in the high-redshift Universe, by studying the Lyman Alpha emission of a system at redshift 3.1 (LAB1). We obtain integral-field spectra to study the distribution of the ionised gas, as well as the emission profile, and discuss possible formation and ionisation scenarios.NWOUBL - phd migration 201
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VADER - A Satellite Mission Concept For High Precision Dark Energy Studies
We present a satellite mission concept to measure the dark energy equation of
state parameter w with percent-level precision. The Very Ambitious Dark Energy
Research satellite (VADER) is a multi-wavelength survey mission joining X-ray,
optical, and IR instruments for a simultaneous spectral coverage from 4microns
(0.3eV) to 10keV over a field of view (FoV) of 1 square degree. VADER combines
several clean methods for dark energy studies, the baryonic acoustic
oscillations in the galaxy and galaxy cluster power spectrum and weak lensing,
for a joint analysis over an unrivalled survey volume. The payload consists of
two XMM-like X-ray telescopes with an effective area of 2,800cm^2 at 1.5keV and
state-of-the-art wide field DEPFET pixel detectors (0.1-10keV) in a curved
focal plane configuration to extend the FoV. The X-ray telescopes are
complemented by a 1.5m optical/IR telescope with 8 instruments for simultaneous
coverage of the same FoV from 0.3 to 4 microns. The 8 dichroic-separated bands
(u,g,r,z,J,H,K,L) provide accurate photometric galaxy redshifts, whereas the
diffraction-limited resolution of the central z-band allows precise shape
measurements for cosmic shear analysis.
The 5 year VADER survey will cover a contiguous sky area of 3,500 square
degrees to a depth of z~2 and will yield accurate photometric redshifts and
multi-wavelength object parameters for about 175,000 galaxy clusters, one
billion galaxies, and 5 million AGN. VADER will not only provide unprecedented
constraints on the nature of dark energy, but will additionally extend and
trigger a multitude of cosmic evolution studies to very large (>10 Gyrs)
look-back times.Comment: 14 pages, 7 figures, accepted for publication in the SPIE conference
proceeding
The challenges of a public data release : behind the scenes of SDSS DR13
The Sloan Digitial Sky Surveys (SDSS) have been collecting imaging and spectoscopic data since 1998. These data as well as their derived data products are made publicly available through regular data releases, of which the 13th took place summer 2016. Although public data releases can be challenging to manage, they significantly increase the impact of a survey, both scientifically and educationally.Postprin
Quadruple-peaked spectral line profiles as a tool to constrain gravitational potential of shell galaxies
Stellar shells observed in many giant elliptical and lenticular as well as a
few spiral and dwarf galaxies, presumably result from galaxy mergers.
Line-of-sight velocity distributions of the shells could, in principle, if
measured with a sufficiently high S/N, constitute one of methods to constrain
the gravitational potential of the host galaxy. Merrifield & Kuijken (1998)
predicted a double-peaked line profile for stationary shells resulting from a
nearly radial minor merger. In this paper, we aim at extending their analysis
to a more realistic case of expanding shells, inherent to the merging process,
whereas we assume the same type of merger and the same orbital geometry. We use
analytical approach as well as test particle simulations to predict the
line-of-sight velocity profile across the shell structure. Simulated line
profiles are convolved with spectral PSFs to estimate the peak detectability.
The resulting line-of-sight velocity distributions are more complex than
previously predicted due to non-zero phase velocity of the shells. In
principle, each of the Merrifield & Kuijken (1998) peaks splits into two,
giving a quadruple-peaked line profile, which allows more precise determination
of the potential of the host galaxy and, moreover, contains additional
information. We find simple analytical expressions that connect the positions
of the four peaks of the line profile and the mass distribution of the galaxy,
namely the circular velocity at the given shell radius and the propagation
velocity of the shell. The analytical expressions were applied to a
test-particle simulation of a radial minor merger and the potential of the
simulated host galaxy was successfully recovered. The shell kinematics can thus
become an independent tool to determine the content and distribution of the
dark matter in shell galaxies, up to ~100 kpc from the center of the host
galaxy.Comment: 15 pages, 16 figures | v2: accepted for publication in A&A, minor
language correction
The HI Tully-Fisher Relation of Early-Type Galaxies
We study the HI K-band Tully-Fisher relation and the baryonic Tully-Fisher
relation for a sample of 16 early-type galaxies, taken from the ATLAS3D sample,
which all have very regular HI disks extending well beyond the optical body (>
5 R_eff). We use the kinematics of these disks to estimate the circular
velocity at large radii for these galaxies. We find that the Tully-Fisher
relation for our early-type galaxies is offset by about 0.5-0.7 magnitudes from
the relation for spiral galaxies. The residuals with respect to the spiral
Tully-Fisher relation correlate with estimates of the stellar mass-to-light
ratio, suggesting that the offset between the relations is mainly driven by
differences in stellar populations. We also observe a small offset between our
Tully-Fisher relation with the relation derived for the ATLAS3D sample based on
CO data representing the galaxies' inner regions (< 1 R_eff). This indicates
that the circular velocities at large radii are systematically 10% lower than
those near 0.5-1 R_eff, in line with recent determinations of the shape of the
mass profile of early-type galaxies. The baryonic Tully-Fisher relation of our
sample is distinctly tighter than the standard one, in particular when using
mass-to-light ratios based on dynamical models of the stellar kinematics. We
find that the early-type galaxies fall on the spiral baryonic Tully-Fisher
relation if one assumes M/L_K = 0.54 M_sun/L_sun for the stellar populations of
the spirals, a value similar to that found by recent studies of the dynamics of
spiral galaxies. Such a mass-to-light ratio for spiral galaxies would imply
that their disks are 60-70% of maximal. Our analysis increases the range of
galaxy morphologies for which the baryonic Tully-Fisher relations holds,
strengthening previous claims that it is a more fundamental scaling relation
than the classical Tully-Fisher relation.Comment: Accepted for publication in Astronomy & Astrophysic
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