47 research outputs found
The curious case of the companion: evidence for cold accretion onto a dwarf satellite near the isolated elliptical NGC 7796
The isolated elliptical (IE) NGC 7796 is accompanied by an interesting
early-type dwarf galaxy, named NGC7796-DW1. It exhibits a tidal tail, very boxy
isophotes, and multiple nuclei or regions (A, B, and C) that are bluer than the
bulk population of the galaxy, indicating a younger age. These properties are
suggestive of a dwarf-dwarf merger remnant. We use the Multi-Unit Spectroscopic
Explorer (MUSE) at the VLT to investigate NGC 7796-DW1. We extract
characteristic spectra to which we apply the STARLIGHT population synthesis
software to obtain ages and metallicities of the various population components
of the galaxy. The galaxy's main body is old and metal-poor. A surprising
result is the extended line emission in the galaxy, forming a ring-like
structure with a projected diameter of 2.2 kpc. The line ratios fall into the
regime of HII-regions, although OB-stellar populations cannot be identified by
spectral signatures. Nucleus A is a relatively old (7 Gyr or older) and
metal-poor super star cluster, most probably the nucleus of the dwarf, now
displaced. The star-forming regions B and C show younger and distinctly more
metal-rich components. The emission line ratios of regions B and C indicate an
almost solar oxygen abundance, if compared with radiation models of HII
regions. NGC7796-DW1 occupies a particular role in the group of transition-type
galaxies with respect to its origin and current evolutionary state, being the
companion of an IE. The dwarf-dwarf merger scenario is excluded because of the
missing metal-rich merger component. A viable alternative is gas accretion from
a reservoir of cold, metal-rich gas. NGC7796 has to provide this gas within its
X-ray bright halo. As illustrated by NGC7796-DW1, cold accretion may be a
general solution to the problem of extended star formation histories in
transition dwarf galaxies. (abridged)Comment: comments: 13 pages, 8 figures, accepted for publication in Astronomy
& Astrophysic
Multi-phase gas interactions on subarcsec scales in the shocked IGM of Stephan's Quintet with JWST and ALMA
We combine JWST and HST imaging with ALMA~CO(2-1) spectroscopy to study the
highly turbulent multi-phase intergalactic medium (IGM) in Stephan's Quintet on
25-150 pc scales. Previous Spitzer observations revealed luminous H line
cooling across a 45 kpc-long filament, created by a giant shock-wave, following
the collision with an intruder galaxy NGC~7318b. We demonstrate that the
MIRI/F1000W/F770W filters are dominated by 0-0~S(3)~H and a combination of
PAH and 0-0~S(5)~H emission. They reveal the dissipation of kinetic energy
as massive clouds experience collisions, interactions and likely
destruction/re-cycling within different phases of the IGM. In one kpc-scaled
structure, warm H formed a triangular-shaped head and tail of compressed
and stripped gas behind a narrow shell of cold H. In another region, two
cold molecular clumps with very different velocities are connected by an
arrow-shaped stream of warm, probably shocked, H suggesting a cloud-cloud
collision is occurring. In both regions, a high warm-to-cold molecular gas
fraction indicates that the cold clouds are being disrupted and converted into
warm gas. We also map gas associated with an apparently forming dwarf galaxy.
We suggest that the primary mechanism for exciting strong mid-IR H lines
throughout Stephan's Quintet is through a fog of warm gas created by the
shattering of denser cold molecular clouds and mixing/recycling in the
post-shocked gas. A full picture of the diverse kinematics and excitation of
the warm H will require future JWST mid-IR spectroscopy. The current
observations reveal the rich variety of ways that different gas phases can
interact with one another.Comment: Accepted for Publications to ApJ April 10 202
Improved Dynamical Constraints on the Masses of the Central Black Holes in Nearby Low-mass Early-type Galactic Nuclei And the First Black Hole Determination for NGC 205
We improve the dynamical black hole (BH) mass estimates in three nearby
low-mass early-type galaxies--NGC 205, NGC 5102, and NGC 5206. We use new
\hst/STIS spectroscopy to fit the star formation histories of the nuclei in
these galaxies, and use these measurements to create local color--mass-to-light
ratio (\ml) relations. We then create new mass models from \hst~imaging and
combined with adaptive optics kinematics, we use Jeans dynamical models to
constrain their BH masses. The masses of the central BHs in NGC 5102 and NGC
5206 are both below one million solar masses and are consistent with our
previous estimates, \Msun~and
\Msun~(3 errors), respectively.
However, for NGC 205, the improved models suggest the presence of a BH for the
first time, with a best-fit mass of
\Msun~(3 errors). This is the least
massive central BH mass in a galaxy detected using any method. We discuss the
possible systematic errors of this measurement in detail. Using this BH mass,
the existing upper limits of both X-ray, and radio emissions in the nucleus of
NGC 205 suggest an accretion rate of the Eddington rate. We
also discuss the color--\mleff~relations in our nuclei and find that the slopes
of these vary significantly between nuclei. Nuclei with significant young
stellar populations have steeper color--\mleff~relations than some previously
published galaxy color--\mleff~relations.Comment: 31 pages, 19 figures, 6 tables, Accepted to Ap
oMEGACat I: MUSE spectroscopy of 300,000 stars within the half-light radius of Centauri
Omega Centauri ( Cen) is the most massive globular cluster of the
Milky Way and has been the focus of many studies that reveal the complexity of
its stellar populations and kinematics. However, most previous studies have
used photometric and spectroscopic datasets with limited spatial or magnitude
coverage, while we aim to investigate it having full spatial coverage out to
its half-light radius and stars ranging from the main sequence to the tip of
the red giant branch. This is the first paper in a new survey of Cen
that combines uniform imaging and spectroscopic data out to its half-light
radius to study its stellar populations, kinematics, and formation history. In
this paper, we present an unprecedented MUSE spectroscopic dataset combining 87
new MUSE pointings with previous observations collected from guaranteed time
observations. We extract spectra of more than 300,000 stars reaching more than
two magnitudes below the main sequence turn-off. We use these spectra to derive
metallicity and line-of-sight velocity measurements and determine robust
uncertainties on these quantities using repeat measurements. Applying quality
cuts we achieve signal-to-noise ratios of 16.47/73.51 and mean metallicity
errors of 0.174/0.031 dex for the main sequence stars (18 mag 22 mag) and red giant branch stars (16 mag 10
mag), respectively. We correct the metallicities for atomic diffusion and
identify foreground stars. This massive spectroscopic dataset will enable
future studies that will transform our understanding of Cen, allowing
us to investigate the stellar populations, ages, and kinematics in great
detail.Comment: 27 pages, 18 figures, 3 tables, accepted for publication in ApJ, the
catalog will be available in the online material of the published articl
ReveaLLAGN 0: First Look at JWST MIRI data of Sombrero and NGC 1052
We present the first results from the Revealing Low-Luminosity Active
Galactic Nuclei (ReveaLLAGN) survey, a JWST survey of seven nearby LLAGN. We
focus on two observations with the Mid-Infrared Instrument's (MIRI) Medium
Resolution Spectrograph (MRS) of the nuclei of NGC 1052 and Sombrero (NGC 4594
/ M104). We also compare these data to public JWST data of a higher-luminosity
AGN, NGC 7319. JWST clearly resolves the AGN component even in Sombrero, the
faintest target in our survey; the AGN components have very red spectra. We
find that the emission-line widths in both NGC 1052 and Sombrero increase with
increasing ionization potential, with FWHM > 1000 km/s for lines with
ionization potential > 50 eV. These lines are also significantly blue-shifted
in both LLAGN. The high ionization potential lines in NGC 7319 show neither
broad widths or significant blue shifts. Many of the lower ionization potential
emission lines in Sombrero show significant blue wings extending > 1000 km/s.
These features and the emission-line maps in both galaxies are consistent with
outflows along the jet direction. Sombrero has the lowest luminosity
high-ionization potential lines ([Ne V] and [O IV]) ever measured in the
mid-IR, but the relative strengths of these lines are consistent with higher
luminosity AGN. On the other hand, the [Ne V] emission is much weaker relative
to the [Ne III}] and [Ne II] lines of higher-luminosity AGN. These initial
results show the great promise that JWST holds for identifying and studying the
physical nature of LLAGN.Comment: Submitted to Ap
oMEGACat III. Multi-band photometry and metallicities reveal spatially well-mixed populations within ω Centauri's half-light radius
ω Centauri, the most massive globular cluster in the Milky Way, has long been suspected to be the stripped nucleus of a dwarf galaxy that fell into the Galaxy a long time ago. There is considerable evidence for this scenario including a large spread in metallicity and an unusually large number of distinct sub-populations seen in photometric studies. In this work, we use new MUSE spectroscopic and HST photometric catalogs to investigate the underlying metallicity distributions as well as the spatial variations of the populations within the cluster up to its half-light radius. Based on 11,050 member stars, the [M/H] distribution has a median of (−1.614±0.003) dex and a large spread of ∼ 1.37 dex reaching from −0.67 dex to −2.04 dex for 99.7 % of the stars. In addition, we show the chromosome map of the cluster, which separates the red giant branch stars into different sub-populations, and analyze the sub-populations of the metal-poorest component. Finally, we do not find any metallicity gradient within the half-light radius, and the different sub-populations are well mixe
oMEGACat I: MUSE spectroscopy of 300,000 stars within the half-light radius of ω Centauri
Omega Centauri (ω Cen) is the most massive globular cluster of the Milky Way and has been the focus of many studies that reveal the complexity of its stellar populations and kinematics. However, most previous studies have used photometric and spectroscopic datasets with limited spatial or magnitude coverage, while we aim to investigate it having full spatial coverage out to its half-light radius and stars ranging from the main sequence to the tip of the red giant branch. This is the first paper in a new survey of ω Cen that combines uniform imaging and spectroscopic data out to its half-light radius to study its stellar populations, kinematics, and formation history. In this paper, we present an unprecedented MUSE spectroscopic dataset combining 87 new MUSE pointings with previous observations collected from guaranteed time observations. We extract spectra of more than 300,000 stars reaching more than two magnitudes below the main sequence turn-off. We use these spectra to derive metallicity and line-of-sight velocity measurements and determine robust uncertainties on these quantities using repeat measurements. Applying quality cuts we achieve signal-to-noise ratios of 16.47/73.51 and mean metallicity errors of 0.174/0.031 dex for the main sequence stars (18 mag < magF625W < 22 mag) and red giant branch stars (16 mag < magF625W <10 mag), respectively. We correct the metallicities for atomic diffusion and identify foreground stars. This massive spectroscopic dataset will enable future studies that will transform our understanding of ω Cen, allowing us to investigate the stellar populations, ages, and kinematics in great detail
Rubin-Euclid Derived Data Products:Initial Recommendations
This report is the result of a joint discussion between the Rubin and Euclid scientific communities. The work presented in this report was focused on designing and recommending an initial set of Derived Data products (DDPs) that could realize the science goals enabled by joint processing. All interested Rubin and Euclid data rights holders were invited to contribute via an online discussion forum and a series of virtual meetings. Strong interest in enhancing science with joint DDPs emerged from across a wide range of astrophysical domains: Solar System, the Galaxy, the Local Volume, from the nearby to the primaeval Universe, and cosmology
Probing the boundary between star clusters and dwarf galaxies: A MUSE view on the dynamics of Crater/Laevens I
We present MUSE observations of the debated ultra faint stellar system Crater. We spectroscopically confirm 26 member stars of this system via radial velocity measure-ments. We derive the systematic instrumental velocity uncertainty of MUSE spectra to be 2.27kms−1. This new dataset increases the confirmed member stars of Crater by a factor of 3. One out of three bright blue stars and a fainter blue star just above the main-sequence-turn-off are also found to be likely members of the system. The ob-servations reveal that Crater has a systemic radial velocity of vsys = 148.18+1.08−1.15 kms−1, whereas the most likely velocity dispersion of this system is σv = 2.04+2.19−1.06 kms−1. The total dynamical mass of the system, assuming dynamical equilibrium is thenMtot = 1.50+4.9−1.2 · 105M implying a mass-to-light ratio of M/LV=8.52+28.0−6.5 M/L, which is consistent with a purely baryonic stellar population within its errors and no sig-nificant evidence for the presence dark matter was found. We also find evidence for a velocity gradient in the radial velocity distribution. We conclude that our findings strongly support that Crater is a faint intermediate-age outer halo globular cluster and not a dwarf galaxy