51 research outputs found
Diffuse interstellar bands {\lambda}5780 and {\lambda}5797 in the Antennae Galaxy as seen by MUSE
ABRIDGED: Diffuse interstellar bands (DIBs) are faint spectral absorption
features of unknown origin. Research on DIBs beyond the Local Group (LG) will
surely blossom in the era of the ELTs. A possibility that needs to be explored
is the use of integral field spectrographs. We do so by using MUSE data for the
Antennae Galaxy, the closest major galaxy merger. High S-to-N spectra were
created by co-adding the signal of many spatial elements. The emission of the
underlying stellar population was modeled using STARLIGHT. To our knowledge, we
have derived the first maps for the DIBs at l5780 and l5797 in galaxies outside
the LG. The l5780 DIB was detected in an area of ~0.6 arcmin2, corresponding to
a linear scale of ~25 kpc2. This region was sampled using >200 independent
lines of sight. The DIB l5797 was detected in >100 independent lines of sight.
Both DIBs are associated with a region with high emission in the HI 21 cm line,
implying a connection between atomic gas and DIBs, as the correlations for the
Milky Way also suggest. Conversely, there is mild spatial association between
the two DIBs and the molecular gas, in agreement with results for our Galaxy
that indicate a lack of correlation between DIBs and molecular gas. The overall
structure for the DIB strength distribution and extinction are comparable.
Within the system, the l5780 DIB clearly correlates with the extinction. Both
DIBs follow the relationship between equivalent width and reddening when data
for several galaxies are considered. Unidentified Infrared emission Bands
(UIBs, likely caused by PAHs) and the l5780 and l5797 DIBs show similar but not
identical spatial distributions. We attribute the differences to extinction
effects without necessarily implying a radically different nature of the
respective carriers. The results illustrate the enormous potential of integral
field spectrographs for extragalactic DIB research.Comment: 12 pages, 13 figures, accepted by Astronomy & Astrophysics; version
corrected by English edito
A catalog of 1.5273 micron diffuse interstellar bands based on APOGEE hot telluric calibrators
High resolution stellar spectroscopic surveys provide massive amounts of
diffuse interstellar bands (DIBs) measurements. Data can be used to study the
distribution of the DIB carriers and those environmental conditions that favor
their formation. In parallel, recent studies have also proved that DIBs
extracted from stellar spectra constitute new tools for building the 3D
structure of the Galactic Interstellar Medium (ISM). The amount of details on
the structure depends directly on the quantity of available lines of sight
(LOS). Therefore there is a need to construct databases of high-quality DIB
measurements as large as possible. We aim at providing the community with a
catalog of high-quality measurements of the 1.5273 micron DIB towards a large
fraction of the Apache Point Observatory Galactic Evolution Experiment (APOGEE)
hot stars observed to correct for the telluric absorption and not used for ISM
studies so far. This catalog would complement the extensive database recently
extracted from the APOGEE observations and used for 3D ISM mapping. We devised
a method to fit the stellar continuum of the hot calibration stars and
extracted the DIB from the normalized spectrum. Severe selection criteria based
on the absorption characteristics are applied to the results. In particular
limiting constraints on the DIB widths and Doppler shifts are deduced from the
HI 21 cm measurements, following a new technique of decomposition of the
emission spectra. From ~16 000 available hot telluric spectra we have extracted
~ 6700 DIB measurements and their associated uncertainties. The statistical
properties of the extracted absorptions are examined and our selection criteria
are shown to provide a robust dataset. The resulting catalog contains the DIB
total equivalent widths, central wavelengths and widths. We briefly illustrate
its potential use for the stellar and interstellar communities.Comment: The Astrophysical Journal Supplement, in press, 35 pages, 14 figure
The MUSE view of the planetary nebula NGC 3132
ABRIDGED: 2D spectroscopic MUSE data for the whole extent of NGC3132 have
been reduced and analised. The dust extinction, electron densities and
temperatures of the ionised gas and abundances were determined. The nebula
presents a complex reddening structure with high values (c(Hb)~0.4) at the rim.
Density maps are compatible with an inner high-ionisation plasma at moderate
high density (~1000cm^-3) while the low-ionisation plasma presents a structure
in density peaking at the rim with values ~700 cm^-3. Median Te using different
diagnostics decreases according to the sequence
[NII],[SII]->[SIII]->[OI]->HeI->PJ. Likewise the range of Te covered by
recombination lines is much larger than those obtained from CELs, with large
spatial variations within the nebula. If these differences were due to the
existence of high density clumps, these spatial variations suggest changes in
the properties and/or distribution of the clumps within the nebula. We
determined a median He/H=0.124. The range of measured ionic abundances for
light elements are compatible with literature values. Our kinematic analysis
nicely illustrates the power of 2D kinematic information in many emission lines
to shed light on the intrinsic structure of the nebula. Our derived velocity
maps support a geometry for the nebula similar to the previously propose
diabolo model, but oriented with its major axis at P.A.~-22^o. We identified
two low-surface brightness arc-like structures towards the northern and
southern tips of the nebula, with high extinction, high helium abundance, and
strong low-ionisation emission lines. They are spatially coincident with some
extended low-surface brightness mid-IR emission. The characteristics of the
features are compatible with being the consequence of precessing jets caused by
the binary star system. This study illustrates the enormous potential of IFS
for the study of Galactic PNe.Comment: 21 pages, 15 figures, 6 tables; accepted by A&
UM 462, a local Green Pea galaxy analog under the MUSE magnifying glass
[ABRIGED] Stellar feedback in high-redshift galaxies plays an important role
in the re-ionization epoch of the Universe. Green Pea galaxies (GPs) postulate
as favorite local laboratories. However, at their typical redshift of
, the most intimate interaction between stars and surrounding ISM
cannot be disentangled. Detailed studies of Blue Compact Dwarf galaxies (BCDs)
are necessary to anchor our investigations on them. We present here a study in
detail UM 462, a BCD with similar properties to GPs uisng high quality optical
IFS data with MUSE. Total oxygen abundance by means of the direct method is
12+(O/H)8.02 and homogenous all over the galaxy, in stark contrast
with the metallicities derived from several strong line methods. The velocity
field for the ionised gas presents a velocity stratification in the area
towards the north with redder velocities in the high ionisation lines and bluer
velocities in the low ionisation lines. This is the only area with velocity
dispersions clearly above the MUSE instrumental width, and it is surrounded by
two 1 kpc-long structures nicknamed \emph{the horns}. We interpret the
observational evidence in that area as a fragmented super-bubble fruit of the
stellar feedback and it may constitute a preferred channel for LyC photons from
the youngest generation of stars to escape. The most recent SF seems to
propagate from the outer to the inner parts of the galaxy, and then from east
to west. We identified a supernova remnant and Wolf-Rayet stars - as traced by
the red bump - that support this picture. The direction of the propagation
implies the presence of younger Wolf-Rayet stars at the maximum in H.
The ensemble of results exemplifies the potential of 2D detailed spectroscopic
studies of dwarf star-forming galaxies at high spatial resolution as key
reference for similar studies on primeval galaxies.Comment: 29 pages, 25 figures; resubmitted to A&A after taking the referee's
comments and suggestions into accoun
Towards DIB mapping in galaxies beyond 100 Mpc. A radial profile of the 5780.5 diffuse interstellar band in AM 1353-272 B
Diffuse Interstellar Bands (DIBs) are non-stellar weak absorption features of
unknown origin found in the spectra of stars viewed through one or several
clouds of Interstellar Medium (ISM). Research of DIBs outside the Milky Way is
currently very limited. Specifically spatially resolved investigations of DIBs
outside of the Local Group is, to our knowledge, inexistent. Here, we explore
the capability of the high sensitivity Integral Field Spectrograph, MUSE, as a
tool to map diffuse interstellar bands at distances larger than 100 Mpc. We use
MUSE commissioning data for AM 1353-272 B, the member with highest extinction
of the "The Dentist's Chair", an interacting system of two spiral galaxies.
High signal-to-noise spectra were created by co-adding the signal of many
spatial elements distributed in a geometry of concentric elliptical half-rings.
We derived decreasing radial profiles for the equivalent width of the
5780.5 DIB both in the receding and approaching side of the companion
galaxy up to distances of 4.6 kpc from the center of the galaxy.
Likewise, interstellar extinction, as derived from the Halpha/Hbeta line ratio
displays a similar trend, with decreasing values towards the external parts.
This translates into an intrinsic correlation between the strength of the DIB
and the extinction within AM 1353-272 B consistent with the current existing
global trend between these quantities when using measurements for both Galactic
and extragalactic sight lines. Mapping of DIB strength in the Local Universe as
up to now only done for the Milky Way seems feasible. This offers a new
approach to study the relationship between DIBs and other characteristics and
species of the ISM in different conditions as those found in our Galaxy to the
use of galaxies in the Local Group and/or single sightlines towards supernovae,
quasars and galaxies outside the Local Group.Comment: 4 pages, 4 figures, accepted for publication as a Letter in Astronomy
and Astrophysics; Received 10 February 2015 / Accepted 20 February 2015 ;
English corrections include
VLT-VIMOS integral field spectroscopy of luminous and ultraluminous infrared galaxies: III. the atlas of the stellar and ionized gas distribution
Context. Luminous and ultraluminous infrared galaxies (LIRGs and ULIRGs) are much more numerous at higher redshifts than locally, dominating the star-formation rate density at redshifts ∼1-2. Therefore, they are important objects in order to understand how galaxies form and evolve through cosmic time. Local samples provide a unique opportunity to study these objects in detail. Aims. We aim to characterize the morphologies of the stellar continuum and the ionized gas (Hα) emissions from local sources, and investigate how they relate with the dynamical status and IR-luminosity of the sources. Methods. We use optical (5250-7450 Å) integral field spectroscopic (IFS) data for a representative sample of 38 sources (31 LIRGs and 7 ULIRGs), taken with the VIMOS instrument on the VLT. Results. We present an atlas of IFS images of continuum emission, Hα emission, and Hα equivalent widths for the sample. The morphologies of the Hα emission are substantially different from those of the stellar continuum. The Hα images frequently reveal extended structures that are not visible in the continuum, such as HII regions in spiral arms, tidal tails, rings, bridges, of up to few kpc from the nuclear regions. The morphologies of the continuum and Hα images are studied on the basis of the C2 kpc parameter, which measures the concentration of the emission within the central 2 kpc. The C2 kpc values found for the Hα images are higher than those of the continuum for the majority (85%) of the objects in our sample. On the other hand, most of the objects in our sample (∼62%) have more than half of their Hα emission outside the central 2 kpc. No clear trends are found between the values of C2 kpc and the IR-luminosity of the sources. On the other hand, our results suggest that the star formation in advance mergers and early-stage interactions is more concentrated than in isolated objects. Finally, we compared the Hα and infrared emissions as tracers of the star-formation activity. We find that the star-formation rates derived using the Hα luminosities generally underpredict those derived using the IR luminosities, even after accounting for reddening effects. © 2011 ESO.Based on observations carried out at the European Southern observatory, Paranal (Chile), Programs 076.B- 0479(A), 078.B-0072(A) and 081.B-0108(A).The Digitized Sky Surveys were produced at the Space Telescope Science Institute under U.S. Government grant NAG W-2166.This work has been supported by the Spanish Ministry of Science and Innovation (MICINN) under grant ESP2007-65475-C02-01. AM-I is supported by the Spanish Ministry of Science and Innovation (MICINN) under program “Specialization in International Organisms”, Ref. ES2006-0003.Peer Reviewe
Integral field spectroscopy based Hα sizes of local luminous and ultraluminous infrared galaxies. A direct comparison with high-z massive star-forming galaxies
[Aims]: We study the analogy between local luminous and ultraluminous infrared galaxies (U/LIRGs) and high-z massive star forming galaxies (SFGs) by comparing their basic Hα structural characteristics, such as size and luminosity surface density, in an homogeneous way (i.e. same tracer, size definition, and similar physical scales). [Methods]: We use integral field spectroscopy (IFS) based Hα emission maps for a representative sample of 54 local U/LIRGs (66 galaxies) observed with INTEGRAL/WHT and VIMOS/VLT. From this initial sample, we select 26 objects with similar Hα luminosities (L(Hα)) to those of massive (i.e. M * ∼ 10 10 M ⊙ or larger) SFGs at z ∼ 2, and observed on similar physical scales. We then directly compare the sizes, and luminosity (and SFR) surface densities of these local and high-z samples. [Results]: The size of the Hα emitting region in the local U/LIRGs that we study has a wide range of values, with r 1/2(Hα) from 0.2 kpc to 7 kpc. However, about two-thirds of local U/LIRGs with L ir > 10 11.4 L ⊙ have compact Hα emission (i.e. r 1/2 2 kpc). These are systems that show evidence of pre-coalescence merger activity and are indistinguishable from the massive high-z SFGs galaxies in terms of their Hα sizes, and luminosity and SFR surface densities. © 2012 ESO.MGM is supported by the German federal department for education and research (BMBF) under the project number 50OS1101. This work has been supported by the Spanish Ministry of Science and Innovation (MICINN) under grants ESP2007-65475- C02-01 and AYA2010-21161-C02-01.Peer Reviewe
Discovery of an old nova remnant in the Galactic globular cluster M 22
A nova is a cataclysmic event on the surface of a white dwarf in a binary
system that increases the overall brightness by several orders of magnitude.
Although binary systems with a white dwarf are expected to be overabundant in
globular clusters (GCs) compared to the Galaxy, only two novae from Galactic
globular clusters have been observed. We present the discovery of an emission
nebula in the Galactic globular cluster M 22 (NGC 6656) in observations made
with the integral-field spectrograph MUSE. We extract the spectrum of the
nebula and use the radial velocity determined from the emission lines to
confirm that the nebula is part of NGC 6656. Emission-line ratios are used to
determine the electron temperature and density. It is estimated to have a mass
of 1 to solar masses. This mass and the emission-line
ratios indicate that the nebula is a nova remnant. Its position coincides with
the reported location of a 'guest star', an ancient Chinese term for
transients, observed in May 48 BCE. With this discovery, this nova may be one
of the oldest confirmed extrasolar events recorded in human history.Comment: 7 pages, 3 figures; accepted for publication in Astronomy &
Astrophysic
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MUSE crowded field 3D spectroscopy in NGC 300: III. Characterizing extremely faint HII regions and diffuse ionized gas
Context. There are known differences between the physical properties of H II and diffuse ionized gas (DIG). However, most of the studied regions in the literature are relatively bright, with log10 L(Hα)[erg s-1] ≳37. Aims. We compiled an extremely faint sample of 390 H II regions with a median Hα luminosity of 34.7 in the flocculent spiral galaxy NGC 300, derived their physical properties in terms of metallicity, density, extinction, and kinematics, and performed a comparative analysis of the properties of the DIG. Methods. We used MUSE data of nine fields in NGC 300, covering a galactocentric distance of zero to ~450 arcsec (~4 projected kpc), including spiral arm and inter-arm regions. We binned the data in dendrogram leaves and extracted all strong nebular emission lines. We identified H II and DIG regions and compared their electron densities, metallicity, extinction, and kinematic properties. We also tested the effectiveness of unsupervised machine-learning algorithms in distinguishing between the H II and DIG regions. Results. The gas density in the H II and DIG regions is close to the low-density limit in all fields. The average velocity dispersion in the DIG is higher than in the H II regions, which can be explained by the DIG being 1.8 kK hotter than H II gas. The DIG manifests a lower ionization parameter than H II gas, and the DIG fractions vary between 15-77%, with strong evidence of a contribution by hot low-mass evolved stars and shocks to the DIG ionization. Most of the DIG is consistent with no extinction and an oxygen metallicity that is indistinguishable from that of the H II gas. We observe a flat metallicity profile in the central region of NGC 300, without a sign of a gradient. Conclusions. The differences between extremely faint H II and DIG regions follow the same trends and correlations as their much brighter cousins. Both types of objects are so heterogeneous, however, that the differences within each class are larger than the differences between the two classes
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