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Radio astronomy began with one array (Jansky's) and one paraboloid of revolution (Reber's) as collecting areas and has now reached the point where a large number of facilities are arrays of paraboloids, each of which would have looked enormous to Reber in 1932. In the process, interferometry has contributed to the counting of radio sources, establishing superluminal velocities in AGN jets, mapping of sources from the bipolar cow shape on up to full grey-scale and colored images, determining spectral energy distributions requiring non-thermal emission processes, and much else. The process has not been free of competition and controversy, at least partly because it is just a little difficult to understand how earth-rotation, aperture-synthesis interferometry works. Some very important results, for instance the mapping of HI in the Milky Way to reveal spiral arms, warping, and flaring, actually came from single moderate-sized paraboloids. The entry of China into the radio astronomy community has given large (40-110 meter) paraboloids a new lease on life.
KMOS is a multi-object near-infrared integral field spectrograph built by a consortium of UK and German institutes for the ESO Paranal Observatory. KMOS completed commissioning at the ESO VLT in Spring 2013 and was made available to the user community from Oct 2013. We present the unique capabilities of KMOS for 3D galaxy surveys and report on the on-sky performance verification measured during three commissioning runs on the ESO VLT in 2012/13 and some of the early science results.
WISH is a new space science mission concept whose primary goal is to study the first galaxies in the early universe. The primary science goal of the WISH mission is to push the high-redshift frontier beyond the epoch of reionization by utilizing its unique imaging and spectrocopic capabilities and the dedicated survey strategy. WISH will be a 1.5m telescope equipped with a 1000 arcmin2 wide-field Near-IR camera to conduct unique ultra-deep and wide-area sky imaging surveys in the wavelength range 1 - 5 μm. A spectroscopic mode (Integral-Field Unit) in the same Near-IR range and with a field of view of 0.5 - 1 arcmin and a spectral resolution R = 1000 is also planned. The difference between WISH and EUCLID in terms of wavelength range explains why the former concentrates on the reionization period while the latter focuses on the universe at z < 3. WISH and JWST feature different instantaneous fields of view and are therefore also very complementary.
In March 2013, the Sydney–AAO Multi-object Integral field spectrograph (SAMI) began a major survey of 3400 galaxies at the AAT, the largest of its kind to date. At the time of writing, over a third of the targets have been observed and the scientific impact has been immediate. The Manga galaxy survey has now started at the SDSS telescope and will target an even larger sample of nearby galaxies. In Australia, the community is now gearing up to deliver a major new facility called Hector that will allow integral field spectroscopy of 100 galaxies observed simultaneously. By the close of the decade, it will be possible to obtain integral field spectroscopy of 100,000 galaxies over 3000 square degrees of sky down to r=17 (median). Many of these objects will have HI imaging from the new ASKAP radio surveys. We discuss the motivation for such a survey and the use of new cosmological simulations that are properly matched to the integral field observations. The Hector survey will open up a new and unique parameter space for galaxy evolution studies.
We present the ambitious project J-PAS, that will cover 8000 deg2 of the northern sky with 54 narrow-band (∼145Å) contiguous filters, all of them in the optical range (3700Å-9200Å). J-PAS will provide a low resolution spectra (R ∼ 50) in every pixel of the northern sky by 2020, leading to excellent photometric redshifts (0.3% uncertainty) of 100 million sources. J-PAS will permit the study of the 2D properties of nearby galaxies with unprecedented statistics. Some viable studies are the distribution of the star formation rate traced by Hα, the stellar populations gradients in elliptical galaxies up to a few effective radii, or the impact of environment in galaxy properties. In summary, J-PAS will bring a superb data set for 3D analysis in the local Universe.
Ever since the pioneering work of Schmidt a half-century ago there has been great interest in finding an appropriate empirical relation that would directly link some property of interstellar gas with the process of star formation within it. Schmidt conjectured that this might take the form of a power-law relation between the rate of star formation (SFR) and the surface density of interstellar gas. However recent observations suggest that a linear scaling relation between the total SFR and the amount of dense gas within molecular clouds appears to be the underlying physical relation that most directly connects star formation with interstellar gas from scales of individual GMCs to those encompassing entire galaxies both near and far. Although Schmidt relations are found to exist within local GMCs, there is no Schmidt relation observed between GMCs. The implications of these results for interpreting and understanding the Kennicutt-Schmidt scaling law for galaxies are discussed.
Here I present results from individual galaxy studies and galaxy surveys in the Local Universe with particular emphasis on the spatially resolved properties of neutral hydrogen gas. The 3D nature of the data allows detailed studies of the galaxy morphology and kinematics, their relation to local and global star formation as well as galaxy environments. I use new 3D visualisation tools to present multi-wavelength data, aided by tilted-ring models of the warped galaxy disks. Many of the algorithms and tools currently under development are essential for the exploration of upcoming large survey data, but are also highly beneficial for the analysis of current galaxy surveys.
I present an overview of new observations of atomic and molecular gas in early-type galaxies, focusing on the Atlas3D project. Our data on stellar kinematics, age and metallicity, and ionized gas kinematics allow us to place the cold gas into the broader context of early-type galaxy assembly and star formation history. The cold gas data also provide valuable constraints for numerical simulations of early-type galaxies.
I have analyzed line-of-sight velocity fields of the stellar and ionized-gas components for the volume-limited sample of nearby lenticular galaxies by using the raw data of the ATLAS-3D survey undertaken with the integral-field spectrograph SAURON. Among 200 nearby lenticular galaxies, I distinguish 20 cases of nearly orthogonal rotation of the inner ionized gas with respect to the central stellar components; so I estimate a frequency of the inner polar disks in nearby S0 galaxies as 10%. Properties of the central stellar populations – mean ages, metallicities, magnesium-to-iron ratios – are derived through the Lick indices. The typical stellar population properties of the polar-disk host galaxies are exactly the same as the stellar population properties of the complete sample.
The Panchromatic Hubble Andromeda Treasury (PHAT) is an HST multi-cycle treasury program that has mapped the resolved stellar populations of ∼1/3 of the disk of M31 from the UV through the near-IR. This data provides color and luminosity information for more than 150 million stars. Using stellar evolution models, we model the optical color-magnitude diagram to derive spatially-resolved recent star formation histories (SFHs) over large areas of M31 with 100 pc resolution. These include individual star-forming regions as well as quiescent portions of the disk. With these gridded SFHs, we create movies of star formation activity to study the evolution of individual star-forming events across the disk. We analyze the structure of star formation and examine the relation between star formation and gas throughout the disk and particularly in the 10-kpc star-forming ring. We find that the ring has been continuously forming stars for at least 500 Myr. As the only large disk galaxy that is close enough to obtain the photometry for this type of spatially-resolved SFH mapping, M31 plays an important role in our understanding of the evolution of an L* galaxy.
We present results of ALMA (Cycle-0) observations of the CO (6-5) line emission and the 435μm continuum of two nearby luminous infrared galaxies (LIRGs) NGC 34 (a major merger with an AGN) and NGC 1614 (a minor merger with a circum-nuclear starburst). Using receivers in the highest frequency ALMA band available (Band-9), these observations achieved the best angular resolutions (∼0″.25) for ALMA Cycle-0 observations and resolved for the first time distributions of warm dense molecular gas (n > 105 cm−3, T > 100 K) in LIRGs with spatial resolutions better than 100 pc. Our ALMA data show a very tight correlation between the CO (6-5) line emission and the 435μm dust continuum emission, suggesting the warm dense molecular gas dominates the ISM in the central kpc of LIRGs, and gas heating and dust heating in the warm dense gas cores are strongly coupled. On the other hand, we saw very different spatial distributions and kinematic properties of warm dense gas in the two LIRGs, indicating that physical conditions in the ISM can be very different in different LIRGs.
We are conducting a multiwavelength study of XUV discs in nearby, gas-rich spiral galaxies combining the available UV (GALEX) observations with H i data obtained at the ATCA as part of the Local Volume HI Survey (LVHIS) project and multi-object fibre spectroscopy obtained using the 2dF/AAOmega instrument at the 3.9m AAT. Here we present the results of the multiwavelength analysis of the galaxy pair NGC 1512/1510. The H i distribution of NGC 1512 is very extended with two pronounced spiral/tidal arms. Hundreds of independent UV-bright regions are associated with dense H i clouds in the galaxy outskirts. We confirm the detection of ionized gas in the majority of them and characterize their physical properties, chemical abundances and kinematics. Both the gas distribution andthe distribution of the star-forming regions are affected by gravitational interactionwith the neighbouring blue compact dwarf galaxy NGC 1510. Our multiwavelength analysis provides new clues about local star-formation processes, the metal redistribution in the outer gaseous discs of spiral galaxies, the importance of galaxy interactions, the fate of the neutral gas and the chemical evolution in nearby galaxies.
We present an overview of the HALOGAS (Hydrogen Accretion in LOcal GAlaxieS) Survey, which is the deepest systematic investigation of cold gas accretion in nearby spiral galaxies to date. Using the deep H i data that form the core of the survey, we are able to detect neutral hydrogen down to a typical column density limit of about 1019 cm−2 and thereby characterize the low surface brightness extra-planar and anomalous-velocity neutral gas in nearby galaxies with excellent spatial and velocity resolution. Through comparison with sophisticated kinematic modeling, our 3D HALOGAS data also allow us to investigate the disk structure and dynamics in unprecedented detail for a sample of this size. Key scientific results from HALOGAS include new insight into the connection between the star formation properties of galaxies and their extended gaseous media, while the developing HALOGAS catalogue of cold gas clouds and streams provides important insight into the accretion history of nearby spirals. We conclude by motivating some of the unresolved questions to be addressed using forthcoming 3D surveys with the modern generation of radio telescopes.
We have studied the kinematic properties of the ionized gas outflows and ambient interstellar medium (ISM) in a large and representative sample of local U/LIRGs (58 systems, 75 galaxies) at galactic and sub-galactic (i.e.,star-forming clumps) scales, thanks to integral field spectroscopy (IFS)-based high signal-to-noise integrated spectra. The main results have been recently presented in Arribas et al. (2014), and are briefly summarized here.
The combination of strong gravitational lensing and stellar kinematics provides a powerful and robust method to investigate the mass and dynamical structure of early-type galaxies. We demonstrate this approach by analysing two massive ellipticals from the XLENS Survey for which both high-resolution HST imaging and X-Shooter spectroscopic observations are available. We adopt a flexible axisymmetric two-component mass model for the lens galaxies, consisting of a generalised NFW dark halo and a realistic self-gravitating stellar mass distribution. For both systems, we put constraints on the dark halo inner structure and flattening, and we find that they are dominated by the luminous component within one effective radius. By comparing the tight inferences on the stellar mass from the combined lensing and dynamics analysis with the values obtained from stellar population studies, we conclude that both galaxies are characterised by a Salpeter-like stellar initial mass function.
We have obtained high spectral resolution (R ≈ 9000), integral field observations of the three spiral galaxies NGC 3521, NGC 7217 and NGC 7331 using the new fiber-based Integral Field Unit instrument VIRUS-W at the 2.7 m telescope of the McDonald Observatory in Texas. Our data allow us to revisit previous claims of counter rotation in these objects. A detailed kinematic decomposition of NGC 7217 shows that no counter rotating stellar component is present. We find that NGC 7217 hosts a low dispersion, rotating disk that is embedded in a high velocity dispersion stellar halo or bulge that is co-rotating with the disk. Due to the very different velocity dispersions (≈ 20 km s−1 vs. 150 km s−1) , we are further able to perform a Lick index analysis on both components separately which indicates that the two stellar populations are clearly separated in (Mgb,〈Fe〉) space. The velocities and dispersions of the faster component are very similar to those of the interstellar gas as measured from the [O iii] emission. Morphological evidence of active star formation in this component further suggests that NGC 7217 may be in the process of (re)growing a disk inside a more massive and higher dispersion stellar halo.
We present here a brief summary of the currenly on-going IFU surveys of galaxies in teh Local Universe, describing their main characteristics, including their sample selections, instrumental setups, wavelength ranges, and area of the galaxies covered. Finally, we make an emphasis on the main characteristics of the CALIFA survey and the more recent results that has been recently published.
Methods to recover the fossil record of galaxy evolution encoded in their optical spectra have been instrumental in processing the avalanche of data from mega-surveys along the last decade, effectively transforming observed spectra onto a long and rich list of physical properties: from stellar masses and mean ages to full star formation histories. This promoted progress in our understanding of galaxies as a whole. Yet, the lack of spatial resolution introduces undesirable aperture effects, and hampers advances on the internal physics of galaxies. This is now changing with 3D surveys. The mapping of stellar populations in data-cubes allows us to figure what comes from where, unscrambling information previously available only in integrated form. This contribution uses our starlight-based analysis of 300 CALIFA galaxies to illustrate the power of spectral synthesis applied to data-cubes. The selected results highlighted here include: (a) The evolution of the mass-metallicity and mass-density-metallicity relations, as traced by the mean stellar metallicity. (b) A comparison of star formation rates obtained from Hα to those derived from full spectral fits. (c) The relation between star formation rate and dust optical depth within galaxies, which turns out to mimic the Schmidt-Kennicutt law. (d) PCA tomography experiments.
We resolve spatially the star formation history of 300 nearby galaxies from the CALIFA integral field survey to investigate: a) the radial structure and gradients of the present stellar populations properties as a function of the Hubble type; and b) the role that plays the galaxy stellar mass and stellar mass surface density in governing the star formation history and metallicity enrichment of spheroids and the disks of galaxies. We apply the fossil record method based on spectral synthesis techniques to recover spatially and temporally resolved maps of stellar population properties of spheroids and spirals with galaxy mass from 109 to 7×1011 M⊙. The individual radial profiles of the stellar mass surface density (μ⋆), stellar extinction (AV), luminosity weighted ages (〈logage〉L), and mass weighted metallicity (〈log Z/Z⊙〉M) are stacked in seven bins of galaxy morphology (E, S0, Sa, Sb, Sbc, Sc and Sd). All these properties show negative gradients as a sight of the inside-out growth of massive galaxies. However, the gradients depend on the Hubble type in different ways. For the same galaxy mass, E and S0 galaxies show the largest inner gradients in μ⋆; and Andromeda-like galaxies (Sb with log M⋆ (M⊙) ∼ 11) show the largest inner age and metallicity gradients. In average, spiral galaxies have a stellar metallicity gradient ∼ −0.1 dex per half-light radius, in agreement with the value estimated for the ionized gas oxygen abundance gradient by CALIFA. A global (M⋆-driven) and local (μ⋆-driven) stellar metallicity relation are derived. We find that in disks, the stellar mass surface density regulates the stellar metallicity; in spheroids, the galaxy stellar mass dominates the physics of star formation and chemical enrichment.
The morphological, spectroscopic and kinematical properties of the warm interstellar medium (wim) in early-type galaxies (ETGs) hold key observational constraints to nuclear activity and the buildup history of these massive quiescent systems. High-quality integral field spectroscopy (IFS) data with a wide spectral and spatial coverage, such as those from the CALIFA survey, offer a precious opportunity for advancing our understanding in this respect. We use deep IFS data from CALIFA (califa.caha.es) to study the wim over the entire extent and optical spectral range of 32 nearby ETGs. We find that all ETGs in our sample show faint (Hα equivalent width EW(Hα)∼0.5 … 2 Å) extranuclear nebular emission extending out to ≥2 Petrosian50 radii. Confirming and strengthening our conclusions in Papaderos et al. (2013, hereafter P13) we argue that ETGs span a broad continuous sequence with regard to the properties of their wim, and they can be roughly subdivided into two characteristic classes. The first one (type i) comprises ETGs with a nearly constant EW(Hα)∼1–3 Å in their extranuclear component, in quantitative agreement with (even though, no proof for) the hypothesis of photoionization by the post-AGB stellar component being the main driver of extended wim emission. The second class (type ii) consists of virtually wim-evacuated ETGs with a large Lyman continuum (Lyc) photon escape fraction and a very low (≤0.5 Å) EW(Hα) in their nuclear zone. These two ETG classes appear indistinguishable from one another by their LINER-specific emission-line ratios. Additionally, here we extend the classification by P13 by the class i+ which stands for a subset of type i ETGs with low-level star-forming activity in contiguous spiral-arm like features in their outermost periphery. These faint features, together with traces of localized star formation in several type i&i+ systems point to a non-negligible contribution from young massive stars to the global ionizing photon budget in ETGs.