ABSTRACT We present an analysis of a deep (1 = 13 Jy) cosmological 1.2 mm continuum map based on ASPECS, the ALMA Spectroscopic Survey in the Hubble Ultra Deep Field. In the 1 arcmin2 covered by ...ASPECS we detect nine sources at significance at 1.2 mm. Our ALMA-selected sample has a median redshift of , with only one galaxy detected at z > 2 within the survey area. This value is significantly lower than that found in millimeter samples selected at a higher flux density cutoff and similar frequencies. Most galaxies have specific star formation rates (SFRs) similar to that of main-sequence galaxies at the same epoch, and we find median values of stellar mass and SFRs of and yr−1, respectively. Using the dust emission as a tracer for the interstellar medium (ISM) mass, we derive depletion times that are typically longer than 300 Myr, and we find molecular gas fractions ranging from ∼0.1 to 1.0. As noted by previous studies, these values are lower than those using CO-based ISM estimates by a factor of ∼2. The 1 mm number counts (corrected for fidelity and completeness) are in agreement with previous studies that were typically restricted to brighter sources. With our individual detections only, we recover 55% 4% of the extragalactic background light (EBL) at 1.2 mm measured by the Planck satellite, and we recover 80% 7% of this EBL if we include the bright end of the number counts and additional detections from stacking. The stacked contribution is dominated by galaxies at , with stellar masses of (1-3) × 1010 M . For the first time, we are able to characterize the population of galaxies that dominate the EBL at 1.2 mm.
ABSTRACT
The physical properties of galactic winds are one of the keys to understand galaxy formation and evolution. These properties can be constrained thanks to background quasar lines of sight ...(LOS) passing near star-forming galaxies (SFGs). We present the first results of the MusE GAs FLOw and Wind survey obtained from two quasar fields, which have eight Mg
ii
absorbers of which three have rest equivalent width greater than 0.8 Å. With the new Multi Unit Spectroscopic Explorer (MUSE) spectrograph on the Very Large Telescope (VLT), we detect six (75%) Mg
ii
host galaxy candidates within a radius of 30″ from the quasar LOS. Out of these six galaxy–quasar pairs, from geometrical argument, one is likely probing galactic outflows, where two are classified as “ambiguous,” two are likely probing extended gaseous disks and one pair seems to be a merger. We focus on the wind-pair and constrain the outflow using a high-resolution quasar spectra from the Ultraviolet and Visual Echelle Spectrograph. Assuming the metal absorption to be due to ga;s flowing out of the detected galaxy through a cone along the minor axis, we find outflow velocities in the order of ≈150
(i.e., smaller than the escape velocity) with a loading factor,
, of ≈0.7. We see evidence for an open conical flow, with a low-density inner core. In the future, MUSE will provide us with about 80 multiple galaxy−quasar pairs in two dozen fields.
Abstract
We present a MUSE (Multi-Unit Spectroscopic Explorer) and KMOS (K-band Multi-Object Spectrograph) dynamical study 405 star-forming galaxies
at redshift z = 0.28–1.65 (median redshift
...$\bar{z}$
= 0.84). Our sample is representative of the star-forming ‘main sequence’, with star formation rates of SFR = 0.1–30 M⊙ yr−1 and stellar masses M
⋆ = 108–1011 M⊙. For 49 ± 4 per cent of our sample, the dynamics suggest rotational support, 24 ± 3 per cent are unresolved systems and 5 ± 2 per cent appear to be early-stage major mergers with components on 8–30 kpc scales. The remaining 22 ± 5 per cent appear to be dynamically complex, irregular (or face-on systems). For galaxies whose dynamics suggest rotational support, we derive inclination-corrected rotational velocities and show that these systems lie on a similar scaling between stellar mass and specific angular momentum as local spirals with j
⋆ = J/
$M_\star \propto M_\star ^{2/3}$
but with a redshift evolution that scales as j
⋆ ∝ M
$_\star ^{2/3}(1+z)^{-1}$
. We also identify a correlation between specific angular momentum and disc stability such that galaxies with the highest specific angular momentum (log(j
⋆/M
$_\star ^{2/3}$
) > 2.5) are the most stable, with Toomre Q = 1.10 ± 0.18, compared to Q = 0.53 ± 0.22 for galaxies with log(j
⋆/M
$_\star ^{2/3}$
) < 2.5. At a fixed mass, the Hubble Space Telescope morphologies of galaxies with the highest specific angular momentum resemble spiral galaxies, whilst those with low specific angular momentum are morphologically complex and dominated by several bright star-forming regions. This suggests that angular momentum plays a major role in defining the stability of gas discs: at z ∼ 1, massive galaxies that have discs with low specific angular momentum are globally unstable, clumpy and turbulent systems. In contrast, galaxies with high specific angular momentum have evolved into stable discs with spiral structure where star formation is a local (rather than global) process.
Aims.
NGC 6240 is a well-studied nearby galaxy system in the process of merging. Based on optical, X-ray, and radio observations, it is thought to harbor two active nuclei. We carried out a detailed ...optical 3D spectroscopic study to investigate the inner region of this system in connection with existing MERLIN and VLBA data.
Methods.
We observed NGC 6240 with very high spatial resolution using the MUSE instrument in the Narrow-Field Mode with the four-laser GALACSI adaptive optics system on the ESO VLT under seeing conditions of 0
″
.
49. Our 3D spectra cover the wavelength range from 4725 to 9350 Å at a spatial resolution of ∼75 mas.
Results.
We report the discovery of three nuclei in the final state of merging within a region of only 1 kpc in the NGC 6240 system. Thanks to MUSE we are able to show that the formerly unresolved southern component actually consists of two distinct nuclei separated by only 198 pc. In combination with
Gaia
data we reach an absolute positional accuracy of only 30 mas that is essential to compare optical spectra with MERLIN and VLBA radio positions.
Conclusions.
The verification and detailed study of a system with three nuclei, two of which are active and each with a mass in excess of 9 × 10
7
M
⊙
, is of great importance for the understanding of hierarchical galaxy formation via merging processes since multiple mergers lead to a faster evolution of massive galaxies in comparison to binary mergers. So far it has been suggested that the formation of galactic nuclei with multiple supermassive black holes (SMBHs) is expected to be rare in the local universe. Triple massive black hole systems might be of fundamental importance for the coalescence of massive black hole binaries in less than a Hubble time leading to the loudest sources of gravitational waves in the millihertz regime.
ABSTRACT We present a search for C ii line and dust continuum emission from optical dropout galaxies at z > 6 using ASPECS, our Atacama Large Millimeter submillimeter Array Spectroscopic Survey in ...the Hubble Ultra-deep Field (UDF). Our observations, which cover the frequency range of 212-272 GHz, encompass approximately the range of 6 < z < 8 for C ii line emission and reach a limiting luminosity of LC ii ∼ (1.6-2.5) × 108 L . We identify 14 C ii line emitting candidates in this redshift range with significances >4.5 , two of which correspond to blind detections with no optical counterparts. At this significance level, our statistical analysis shows that about 60% of our candidates are expected to be spurious. For one of our blindly selected C ii line candidates, we tentatively detect the CO(6-5) line in our parallel 3 mm line scan. None of the line candidates are individually detected in the 1.2 mm continuum. A stack of all C ii candidates results in a tentative detection with S1.2 mm = 14 5 Jy. This implies a dust-obscured star-formation rate (SFR) of (3 1) M yr−1. We find that the two highest-SFR objects have candidate C ii lines with luminosities that are consistent with the low-redshift LC ii versus SFR relation. The other candidates have significantly higher C ii luminosities than expected from their UV-based SFR. At the current sensitivity, it is unclear whether the majority of these sources are intrinsically bright C ii emitters, or spurious sources. If only one of our line candidates was real (a scenario greatly favored by our statistical analysis), we find a source density for C ii emitters at 6 < z < 8 that is significantly higher than predicted by current models and some extrapolations from galaxies in the local universe.
The ATLAS3D project is a multiwavelength survey combined with a theoretical modelling effort. The observations span from the radio to the millimetre and optical, and provide multicolour imaging, ...two-dimensional kinematics of the atomic (H i), molecular (CO) and ionized gas (Hβ, O iii and N i), together with the kinematics and population of the stars (Hβ, Fe5015 and Mg b), for a carefully selected, volume-limited (1.16 × 105 Mpc3) sample of 260 early-type (elliptical E and lenticular S0) galaxies (ETGs). The models include semi-analytic, N-body binary mergers and cosmological simulations of galaxy formation. Here we present the science goals for the project and introduce the galaxy sample and the selection criteria. The sample consists of nearby (D < 42 Mpc, |δ− 29°| < 35°, |b| > 15°) morphologically selected ETGs extracted from a parent sample of 871 galaxies (8 per cent E, 22 per cent S0 and 70 per cent spirals) brighter than MK
< −21.5 mag (stellar mass M
★≳ 6 ×109 M⊙). We analyse possible selection biases and we conclude that the parent sample is essentially complete and statistically representative of the nearby galaxy population. We present the size-luminosity relation for the spirals and ETGs and show that the ETGs in the ATLAS3D sample define a tight red sequence in a colour-magnitude diagram, with few objects in the transition from the blue cloud. We describe the strategy of the SAURON integral field observations and the extraction of the stellar kinematics with the ppxf method. We find typical 1σ errors of ΔV≈ 6 km s−1, Δσ≈ 7 km s−1, Δh
3≈Δh
4≈ 0.03 in the mean velocity, the velocity dispersion and Gauss-Hermite (GH) moments for galaxies with effective dispersion σe≳ 120 km s−1. For galaxies with lower σe (≈40 per cent of the sample) the GH moments are gradually penalized by ppxf towards zero to suppress the noise produced by the spectral undersampling and only V and σ can be measured. We give an overview of the characteristics of the other main data sets already available for our sample and of the ongoing modelling projects.
Abstract
Conceived over 30 years ago, photoconductive (PC) emitters have proved essential in the development and spread of terahertz technology. Since then, not only have they been used extensively ...in a wide range of spectroscopic and imaging applications, they have also undergone significant improvements in performance, leading to their use for broadband or non-linear spectroscopy. In this review article, we provide an overview of the literature, highlighting the key milestones in the progression of the PC emitter. We also investigate the future of PC technology and review the existing challenges.
Galaxies are surrounded by large reservoirs of gas, mostly hydrogen, that are fed by inflows from the intergalactic medium and by outflows from galactic winds. Absorption-line measurements along the ...lines of sight to bright and rare background quasars indicate that this circumgalactic medium extends far beyond the starlight seen in galaxies, but very little is known about its spatial distribution. The Lyman-α transition of atomic hydrogen at a wavelength of 121.6 nanometres is an important tracer of warm (about 10
kelvin) gas in and around galaxies, especially at cosmological redshifts greater than about 1.6 at which the spectral line becomes observable from the ground. Tracing cosmic hydrogen through its Lyman-α emission has been a long-standing goal of observational astrophysics
, but the extremely low surface brightness of the spatially extended emission is a formidable obstacle. A new window into circumgalactic environments was recently opened by the discovery of ubiquitous extended Lyman-α emission from hydrogen around high-redshift galaxies
. Such measurements were previously limited to especially favourable systems
or to the use of massive statistical averaging
because of the faintness of this emission. Here we report observations of low-surface-brightness Lyman-α emission surrounding faint galaxies at redshifts between 3 and 6. We find that the projected sky coverage approaches 100 per cent. The corresponding rate of incidence (the mean number of Lyman-α emitters penetrated by any arbitrary line of sight) is well above unity and similar to the incidence rate of high-column-density absorbers frequently detected in the spectra of distant quasars
. This similarity suggests that most circumgalactic atomic hydrogen at these redshifts has now been detected in emission.
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