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Register a new userAperture corrections for disk galaxy properties derived from the CALIFA survey. Balmer emission lines in spiral galaxies
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This work investigates the effect of the aperture size on derived galaxy properties for which we have spatially-resolved optical spectra. We focus on some indicators of star formation activity and dust attenuation for spiral galaxies that have been widely used in previous work on galaxy evolution. We have used 104 spiral galaxies from the CALIFA survey for which 2D spectroscopy with complete spatial coverage is available. From the 3D cubes we have derived growth curves of the most conspicuous Balmer emission lines (Halpha, Hbeta) for circular apertures of different radii centered at the galaxys nucleus after removing the underlying stellar continuum. We find that the Halpha flux (f(Halpha)) growth curve follows a well defined sequence with aperture radius showing low dispersion around the median value. From this analysis, we derive aperture corrections for galaxies in different magnitude and redshift intervals. Once stellar absorption is properly accounted for, the f(Halpha)/f(Hbeta) ratio growth curve shows a smooth decline, pointing towards the absence of differential dust attenuation as a function of radius. Aperture corrections as a function of the radius are provided in the interval [0.3,2.5]R_50. Finally, the Halpha equivalent width (EW(Halpha)) growth curve increases with the size of the aperture and shows a very large dispersion for small apertures. This large dispersion prevents the use of reliable aperture corrections for this quantity. In addition, this result suggests that separating star-forming and quiescent galaxies based on observed EW(Halpha) through small apertures is likely to result in low EW(Halpha) star-forming galaxies begin classified as quiescent.
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We present the stellar kinematic maps of a large sample of galaxies from the integral-field spectroscopic survey CALIFA. The sample comprises 300 galaxies displaying a wide range of morphologies across the Hubble sequence, from ellipticals to late-type spirals. This dataset allows us to homogeneously extract stellar kinematics up to several effective radii. In this paper, we describe the level of completeness of this subset of galaxies with respect to the full CALIFA sample, as well as the virtues and limitations of the kinematic extraction compared to other well-known integral-field surveys. In addition, we provide averaged integrated velocity dispersion radial profiles for different galaxy types, which are particularly useful to apply aperture corrections for single aperture measurements or poorly resolved stellar kinematics of high-redshift sources. The work presented in this paper sets the basis for the study of more general properties of galaxies that will be explored in subsequent papers of the survey.
We present a study of the integrated properties of the 835 galaxies in the CALIFA survey. To derive the main physical parameters of the galaxies we have fitted their UV-to-IR spectral energy distributions (SED) with sets of theoretical models using CIGALE. We perform a comparison of the integrated galaxy parameters derived from multi-band SED fitting with those obtained from modelling the Integral Field Unit (IFU) spectra and show the clear advantage of using the SED-derived star formation rates (SFR). A detailed analysis of galaxies in the SFR/Mstar plane as a function of their properties reveals that quenching of star formation is caused by a combination of gas deficiency and the inefficiency of the existing gas to form new stars. Exploring the plausible mechanisms that could produce this effect, we find a strong correlation with galaxy morphology and the build-up of central bulge. On the other hand, the presence of AGN and/or a stellar bar, as well as the local environment have only temporal effects on the current star formation, a result also consistent with their model-derived star formation histories.
In view of both the size of its gap and the previously reported asymmetries and near-infrared spiral arms, the transition disk of the Herbig Fe star HD 142527 constitutes a remarkable case study. This paper focuses on the morphology of the outer disk through ALMA observations of $^{12}$CO J=2-1, $^{12}$CO J=3-2 and $^{13}$CO J=2-1. Both $^{12}$CO J=2-1 and $^{12}$CO J=3-2 show spiral features of different sizes. The innermost spiral arm (S1) is a radio counterpart of the first near-infrared spiral observed by Fukagawa et al. (2006), but it is shifted radially outward. However, the most conspicuous CO spiral arm (S2) lies at the outskirts of the disk and had not been detected before. It corresponds to a cold density structure, with both brightness and excitation temperatures of order 13$pm$2 K and conspicuous in the $^{12}$CO J=2-1 peak-intensity map, but faint in $^{12}$CO J=3-2. There is also a faint counterarm (S3), point-symmetrical of S2 with respect to the star. These three spirals are modelled separately with two different formulae that approximate the loci of density maxima in acoustic waves due to embedded planets. S1 could be fit relatively well with these formulae, compared to S2 and S3. Alternative scenarios such as gravitational instability or external tidal interaction are discussed. The impact of channelization on spectrally and spatially resolved peak intensity maps is also briefly addressed.
High signal-to-noise, representative spectra of star-forming galaxies at z~2, obtained via stacking, reveal a high-velocity component underneath the narrow H-alpha and [NII] emission lines. When modeled as a single Gaussian, this broad component has FWHM > 1500 km/s; when modeled as broad wings on the H-alpha and [NII] features, it has FWHM > 500 km/s. This feature is preferentially found in the more massive and more rapidly star-forming systems, which also tend to be older and larger galaxies. We interpret this emission as evidence of either powerful starburst-driven galactic winds or active supermassive black holes. If galactic winds are responsible for the broad emission, the observed luminosity and velocity of this gas imply mass outflow rates comparable to the star formation rate. On the other hand, if the broad line regions of active black holes account for the broad feature, the corresponding black holes masses are estimated to be an order of magnitude lower than those predicted by local scaling relations, suggesting a delayed assembly of supermassive black holes with respect to their host bulges.
[Abridged] Within the hierarchical framework for galaxy formation, minor merging and tidal interactions are expected to shape all large galaxies to the present day. As a consequence, most seemingly normal disk galaxies should be surrounded by spatially extended stellar tidal features of low surface brightness. As part of a pilot survey for such interaction signatures, we have carried out ultra deep, wide field imaging of 8 isolated spiral galaxies in the Local Volume, with data taken at small (D=0.1-0.5m) robotic telescopes that provide exquisite surface brightness sensitivity (mu_V)~28.5$ mag/arcsec^2). This initial observational effort has led to the discovery of six previously undetected extensive (to ~30 kpc) stellar structures in the halos surrounding these galaxies, likely debris from tidally disrupted satellites. In addition, we confirm and clarify several enormous stellar over-densities previously reported in the literature, but never before interpreted as tidal streams. Even this pilot sample of galaxies exhibits strikingly diverse morphological characteristics of these extended stellar features: great circle-like features that resemble the Sagittarius stream surrounding the Milky Way, remote shells and giant clouds of presumed tidal debris far beyond the main stelar body, as well as jet-like features emerging from galactic disks. A qualitative comparison with available simulations set in a Lambda-Cold Dark Matter cosmology shows that the extraordinary variety of stellar morphologies detected in this pilot survey matches that seen in those simulations. The common existence of these tidal features around normal disk galaxies and the morphological match to the simulations constitutes new evidence that these theoretical models also apply to a large number of other Milky Way-mass disk galaxies in the Local Volume.
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