We observed Hubble Deep Field South with the new panoramic integral-field spectrograph MUSE that we built and have just commissioned at the VLT. The data cube resulting from 27 h of integration ...covers one arcmin2 field of view at an unprecedented depth with a 1σ emission-line surface brightness limit of 1 × 10-19 erg s-1 cm-2 arcsec-2, and contains ~90 000 spectra. We present the combined and calibrated data cube, and we performed a first-pass analysis of the sources detected in the Hubble Deep Field South imaging. We measured the redshifts of 189 sources up to a magnitude I814 = 29.5, increasing the number of known spectroscopic redshifts in this field by more than an order of magnitude. We also discovered 26 Lyα emitting galaxies that are not detected in the HST WFPC2 deep broad-band images. The intermediate spectral resolution of 2.3 Å allows us to separate resolved asymmetric Lyα emitters, O ii3727 emitters, and C iii1908 emitters, and the broad instantaneous wavelength range of 4500 Å helps to identify single emission lines, such as O iii5007, Hβ, and Hα, over a very wide redshift range. We also show how the three-dimensional information of MUSE helps to resolve sources that are confused at ground-based image quality. Overall, secure identifications are provided for 83% of the 227 emission line sources detected in the MUSE data cube and for 32% of the 586 sources identified in the HST catalogue. The overall redshift distribution is fairly flat to z = 6.3, with a reduction between z = 1.5 to 2.9, in the well-known redshift desert. The field of view of MUSE also allowed us to detect 17 groups within the field. We checked that the number counts of O ii3727 and Lyα emitters are roughly consistent with predictions from the literature. Using two examples, we demonstrate that MUSE is able to provide exquisite spatially resolved spectroscopic information on the intermediate-redshift galaxies present in the field. Thisunique data set can be used for a wide range of follow-up studies. We release the data cube, the associated products, and the source catalogue with redshifts, spectra, and emission-line fluxes.
We quantify the stellar rotation of galaxies by computing the $ R $ parameter, a proxy for the stellar angular momentum in a sample of 106 intermediate-redshift galaxies (0.1 $<$ z $<$ 0.8). The ...sample is located in the CANDELS/GOODS-S and CANDELS/COSMOS regions, and it was observed by various MUSE surveys. We created spatially resolved stellar velocity and velocity dispersion maps using a full-spectrum fitting technique, covering spatially sim 2$R_ e $ for the galaxies. The sample spans stellar masses from sim 10$^ $ M$_ odot $ to 10$^ $ M$_ odot $ with star formation rates (SFRs) from log$_ $(SFR) approx -3 M$_ odot $yr$^ $ to approx 1.7 M$_ odot $yr$^ $ over a range of 6 Gyr in cosmic time. We studied how the atmospheric seeing, introduced by the instrumental point spread function (PSF), affects the measured spin parameter, and we applied corrections when pertinent. Through the analysis of the $ R diagram, we note that the fraction of round and massive galaxies increases with redshift. We did not measure any galaxy with $ R $ < 0.1 in the sample, and we found only one potential (but uncertain) low-mass slow rotator at z $ more similar to the z=0 low-mass slow rotators characterized by counter-rotation than to massive ellipticals. Moreover, we do not see an evident evolution or trend in the stellar angular momentum with redshift. We characterized the galaxy environment using two different indicators: a local estimator based on the Voronoi tesselation method, and a global estimator derived by the use of the friends-of-friends (FoF) algorithm. We find no correlation between the environment and $ R $ given that we are not probing dense regions or massive galaxy structures. We also analysed the kinematic maps of the sample finding that about 40<!PCT!> of the galaxies are consistent with being regular rotators (RRs), having rotating stellar discs with flat velocity dispersion maps, while $ have complex velocity maps and can be identified as non-regular rotators in spite of their $ R $ values. For the remaining galaxies the classification is uncertain. As we lack galaxies with $ R $ < 0.1 in the sample, we are not able to identify when galaxies lose their angular momentum and become slow rotators within the surveyed environments, area, and redshift range.
Aims. At intermediate redshift, galaxy groups and clusters are thought to impact galaxy properties such as their angular momentum. We investigate whether the environment has an impact on the ...galaxies’ stellar angular momentum and identify underlying driving physical mechanisms. Methods. We derived robust estimates of the stellar angular momentum using Hubble Space Telescope (HST) images combined with spatially resolved ionised gas kinematics from the Multi-Unit Spectroscopic Explorer (MUSE) for a sample of ∼200 galaxies in groups and in the field at z ∼ 0.7 drawn from the MAGIC survey. Using various environmental tracers, we study the position of the galaxies in the angular momentum–stellar mass (Fall) relation as a function of environment. Results. We measured a 0.12 dex (2 σ significant) depletion of stellar angular momentum for low-mass galaxies ( M ⋆ < 10 10 M ⊙ ) located in groups with respect to the field. Massive galaxies located in dense environments have less angular momentum than expected from the low-mass Fall relation but, without a comparable field sample, we cannot infer whether this effect is mass or environmentally driven. Furthermore, these massive galaxies are found in the central parts of the structures and have low systemic velocities. The observed depletion of angular momentum at low stellar mass does not appear linked with the strength of the over-density around the galaxies but it is strongly correlated with (i) the systemic velocity of the galaxies normalised by the dispersion of their host group and (ii) their ionised gas velocity dispersion. Conclusions. Galaxies in groups appear depleted in angular momentum, especially at low stellar mass. Our results suggest that this depletion might be induced by physical mechanisms that scale with the systemic velocity of the galaxies (e.g., stripping or merging) and that such a mechanism might be responsible for enhancing the velocity dispersion of the gas as galaxies lose angular momentum.
Kinematics of galaxies in compact groups Torres-Flores, S.; Mendes de Oliveira, C.; Amram, P. ...
Astronomy and astrophysics (Berlin),
10/2010, Letnik:
521
Journal Article
Recenzirano
Odprti dostop
We obtained new Fabry-Perot data cubes and derived velocity fields, monochromatic, and velocity dispersion maps for 28 galaxies in the Hickson compact groups 37, 40, 47, 49, 54, 56, 68, 79, and 93. ...We also derived rotation curves for 9 of the studied galaxies, 6 of which are strongly asymmetric. Combining these new data with previously published 2D kinematic maps of compact group galaxies, we investigated the differences between the kinematic and morphological position angles for a sample of 46 galaxies. We find that one third of the unbarred compact group galaxies have position angle misalignments between the stellar and gaseous components. This and the asymmetric rotation curves are clear signatures of kinematic perturbations, probably because of interactions among compact group galaxies. A comparison between the B-band Tully-Fisher relation for compact group galaxies and for the GHASP field-galaxy sample shows that, despite the high fraction of compact group galaxies with asymmetric rotation curves, these lay on the TF relation defined by galaxies in less dense environments, although with more scatter. This agrees with previous results, but now confirmed for a larger sample of 41 galaxies. We confirm the tendency for compact group galaxies at the low-mass end of the Tully-Fisher relation (HCG 49b, 89d, 96c, 96d, and 100c) to have either a magnitude that is too bright for its mass (suggesting brightening by star formation) and/or a low maximum rotational velocity for its luminosity (suggesting tidal stripping). These galaxies are outside the Tully Fisher relation at the 1σ level, even when the minimum acceptable values of inclinations are used to compute their maximum velocities. Including such galaxies with v < 100 km s-1 in the determination of the zero point and slope of the compact group B-band Tully-Fisher relation would strongly change the fit, making it different from the relation for field galaxies, which has to be kept in mind when studying scaling relations of interacting galaxies, especially at high redshifts.
Context. Identifying the main processes of galaxy assembly at high redshifts is still a major issue in understanding galaxy formation and evolution at early epochs in the history of the Universe. ...Aims. This work aims to provide a first insight into the dynamics and mass assembly of galaxies at redshifts $1.2 < z < 1.6$, the early epoch just before the sharp decrease of the cosmic star formation rate. Methods. We use the near-infrared integral field spectrograph SINFONI on the ESO-VLT under 0.65´´ seeing to obtain spatially resolved spectroscopy on nine emission line galaxies with $1.2 \leq z \leq 1.6$ from the VIMOS VLT Deep Survey. We derive the velocity fields and velocity dispersions on kpc scales using the Hα emission line. Results. Out of the nine star-forming galaxies, we find that galaxies are distributed in three groups: two galaxies can be well reproduced by a rotating disk, three systems can be classified as major mergers and four galaxies show disturbed dynamics and high velocity dispersion. We argue that there is evidence for hierarchical mass assembly from major merging, with most massive galaxies with $M>10^{11}~{M_\odot}$ subject to at least one major merger over a 3 Gyr period as well as for continuous accretion feeding strong star formation. Conclusions. These results point towards a galaxy formation and assembly scenario which involves several processes, possibly acting in parallel, with major mergers and continuous gas accretion playing a major role. Well controlled samples representative of the bulk of the galaxy population at this key cosmic time are necessary to make further progress.
The Virgo Environmental Survey Tracing Ionised Gas Emission (VESTIGE) is a blind narrow-band (NB)
Hα
+NII imaging survey carried out with MegaCam at the Canada–France–Hawaii Telescope. The survey ...covers the whole Virgo cluster region from its core to one virial radius (104 deg
2
). The sensitivity of the survey is of
f
(
Hα
) ~ 4 × 10
−17
erg s
−1
cm
−2
(5
σ
detection limit) for point sources and Σ(
Hα
) ~ 2 × 10
−18
erg s
−1
cm
−2
arcsec
−2
(1
σ
detection limit at 3 arcsec resolution) for extended sources, making VESTIGE the deepest and largest blind NB survey of a nearby cluster. This paper presents the survey in all its technical aspects, including the survey design, the observing strategy, the achieved sensitivity in both the NB
Hα
+NII and in the broad-band
r
filter used for the stellar continuum subtraction, the data reduction, calibration, and products, as well as its status after the first observing semester. We briefly describe the
Hα
properties of galaxies located in a 4 × 1 deg
2
strip in the core of the cluster north of M87, where several extended tails of ionised gas are detected. This paper also lists the main scientific motivations for VESTIGE, which include the study of the effects of the environment on galaxy evolution, the fate of the stripped gas in cluster objects, the star formation process in nearby galaxies of different type and stellar mass, the determination of the
Hα
luminosity function and of the
Hα
scaling relations down to ~10
6
M
⊙
stellar mass objects, and the reconstruction of the dynamical structure of the Virgo cluster. This unique set of data will also be used to study the HII luminosity function in hundreds of galaxies, the diffuse
Hα
+NII emission of the Milky Way at high Galactic latitude, and the properties of emission line galaxies at high redshift.
Aims.
We present new 2D high resolution Fabry–Perot spectroscopic observations of 152 star-forming galaxies that are part of the
Herschel
Reference Survey (HRS), which is a complete
K
-band selected, ...volume-limited sample of nearby galaxies that spans a wide range of stellar mass and morphological types.
Methods.
By using improved data reduction techniques, that provide adaptive binning based on Voronoi tessellation, and using large field-of-view observations, we derived high spectral resolution (
R
> 10 000) H
α
datacubes from which we computed H
α
maps and radial 2D velocity fields that are based on several of thousand independent measurements. A robust method based on such fields allowed us to accurately compute rotation curves and kinematical parameters, for which uncertainties are calculated using a method based on the power spectrum of the residual velocity fields.
Results.
We checked the consistency of the rotation curves by comparing our maximum rotational velocities to those derived from H
I
data, and by computing the
i
-band, NIR, stellar, and baryonic Tully-Fisher relations. We used this set of kinematical data combined with those available at other frequencies to study, for the first time, the relation between the dynamical and the total baryonic mass (stars, atomic and molecular gas, metals, and dust) and to derive the baryonic and dynamical main sequence on a representative sample of the local universe.
The Virgo Environmental Survey Tracing Ionised Gas Emission (VESTIGE) is a blind narrow-band H
α
+ NII imaging survey of the Virgo cluster carried out with MegaCam at the Canada-French-Hawaii ...telescope. We use a new set of data extracted from VESTIGE to study the impact of the hostile cluster environment on the star formation process down to the scale of HII regions (∼50 pc). Here, HII regions are identified and their parameters measured using the HII
PHOT
code on a sample of 114 late-type galaxies spanning a wide range in morphological type (Sa-Sd, Im, BCD), stellar mass (10
6.5
≤
M
star
≤ 10
11
M
⊙
), and star formation activity (10
−3
≤ SFR ≤ 10
M
⊙
yr
−1
). Owing to the exquisite average resolution of the VESTIGE data (0.65 arcsec), we detect 11302 HII regions with an H
α
luminosity
L
(H
α
) ≥ 10
37
erg s
−1
. We show that the typical number of HII regions in gas-stripped objects is significantly lower than in healthy late-types of similar stellar mass. We also show that in these gas-stripped galaxies the number of HII regions significantly drops outside the effective radius, suggesting that the quenching process occurs outside-in, in agreement with other multifrequency observations. These new results consistently confirm that the main mechanism responsible for the decrease of the star formation activity observed in cluster galaxies is ram pressure, allowing us to discard other milder processes such as starvation or strangulation, which are unable to reproduce the observed radially truncated profiles.
We observed the late-type peculiar galaxy NGC 4424 during the Virgo Environmental Survey Tracing Galaxy Evolution (VESTIGE), a blind narrow-band H
α
+NII imaging survey of the Virgo cluster carried ...out with MegaCam at the Canada-French-Hawaii Telescope (CFHT). The presence of a ∼110 kpc (in projected distance) HI tail in the southern direction indicates that this galaxy is undergoing a ram pressure stripping event. The deep narrow-band image revealed a low surface brightness (Σ(H
α
) ≃ 4 × 10
−18
erg s
−1
cm
−2
arcsec
−2
) ionised gas tail ∼10 kpc in length extending from the centre of the galaxy to the north-west, thus in the direction opposite to the HI tail.
Chandra
and XMM X-rays data do not show a compact source in the nucleus or an extended tail of hot gas, while IFU spectroscopy (MUSE) indicates that the gas is photo-ionised in the inner regions and shock-ionised in the outer parts. Medium-resolution (MUSE) and high-resolution (Fabry-Perot) IFU spectroscopy confirms that the ionised gas is kinematically decoupled from the stellar component and indicates the presence of two kinematically distinct structures in the stellar disc. The analysis of the SED of the galaxy indicates that the activity of star formation was totally quenched in the outer disc ∼250–280 Myr ago, while only reduced by ∼80% in the central regions. All this observational evidence suggests that NGC 4424 is the remnant of an unequal-mass merger that occurred ≲500 Myr ago when the galaxy was already a member of the Virgo cluster, and is now undergoing a ram pressure stripping event that has removed the gas and quenched the activity of star formation in the outer disc. The tail of ionised gas probably results from the outflow produced by a central starburst fed by the collapse of gas induced by the merging episode. This outflow is sufficiently powerful to overcome the ram pressure induced by the intracluster medium on the disc of the galaxy crossing the cluster. This analysis thus suggests that feedback can participate in the quenching process of galaxies in high-density regions.
We present the mass models of 31 spiral and irregular nearby galaxies obtained using hybrid rotation curves (RCs) combining high-resolution GHASP Fabry–Perot H α RCs and extended WHISP H i ones ...together with 3.4 |$\mu$|m WISE photometry. The aim is to compare the dark matter (DM) halo properties within the optical radius using only H α RCs with the effect of including and excluding the mass contribution of the neutral gas component, and when using H i or hybrid RCs. Pseudo-isothermal (ISO) core and Navarro–Frenk–White (NFW) cuspy DM halo profiles are used with various fiducial fitting procedures. Mass models using H α RCs including or excluding the H i gas component provide compatible disc M/L. The correlations between DM halo and baryon parameters do not strongly depend on the RC. Clearly, the differences between the fitting procedures are larger than between the different data sets. Hybrid and H i RCs lead to higher M/L values for both ISO and NFW best-fitting models but lower central densities for ISO haloes and higher concentration for NFW haloes than when using H α RCs only. The agreement with the mass model parameters deduced using hybrid RCs, considered as a reference, is better for H i than for H α RCs. ISO density profiles better fit the RCs than the NFW ones, especially when using H α or hybrid RCs. Halo masses at the optical radius determined using the various data sets are compatible even if they tend to be overestimated with H α RCs. Hybrid RCs are thus ideal to study the mass distribution within the optical radius.
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