In the early 1960s, astronomers were puzzled by quasars — sources of intense radio emission that seemed to be stars, but had unintelligible optical spectra. In 1963, Maarten Schmidt solved the puzzle by recognizing the Balmer lines of hydrogen, strongly redshifted, in the spectrum of the quasar 3C 273. Schmidt reached the "most direct and least objectionable" conclusion, that 3C 273 was no star, but the enormously bright nucleus of a distant galaxy.

3C 273: A Star-like Object with Large Red-Shift

Mapping Nearby Galaxies at Apache Point Observatory (MaNGA) is an optical fiber-bundle integral-field unit (IFU) spectroscopic survey that is one of three core programs in the fourth-generation Sloan Digital Sky Survey (SDSS-IV). With a spectral coverage of 3622–10354 A and an average footprint of ~500 arcsec2 per IFU the scientific data products derived from MaNGA will permit exploration of the internal structure of a statistically large sample of 10,000 low-redshift galaxies in unprecedented detail. Comprising 174 individually pluggable science and calibration IFUs with a near-constant data stream, MaNGA is expected to obtain ~100 million raw-frame spectra and ~10 million reduced galaxy spectra over the six-year lifetime of the survey. In this contribution, we describe the MaNGA Data Reduction Pipeline algorithms and centralized metadata framework that produce sky-subtracted spectrophotometrically calibrated spectra and rectified three-dimensional data cubes that combine individual dithered observations. For the 1390 galaxy data cubes released in Summer 2016 as part of SDSS-IV Data Release 13, we demonstrate that the MaNGA data have nearly Poisson-limited sky subtraction shortward of ~8500 A and reach a typical 10σ limiting continuum surface brightness μ = 23.5 AB arcsec-2 in a five-arcsecond-diameter aperture in the g-band. The wavelength calibration of the MaNGA data is accurate to 5 km s-1 rms, with a median spatial resolution of 2.54 arcsec FWHM (1.8 kpc at the median redshift of 0.037) and a median spectral resolution of σ = 72 km s-1.

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The data reduction pipeline for the SDSS-IV MaNGA IFU Galaxy Survey

We study the spatially resolved excitation properties of the ionised gas in a sample of 646 galaxies using integral field spectroscopy data from SDSS-IV MaNGA. Making use of Baldwin-Philips-Terlevich diagnostic diagrams we demonstrate the ubiquitous presence of extended (kpc scale) low ionisation emission-line regions (LIERs) in both star forming and quiescent galaxies. In star forming galaxies LIER emission can be associated with diffuse ionised gas, most evident as extra-planar emission in edge-on systems. In addition, we identify two main classes of galaxies displaying LIER emission: `central LIER' (cLIER) galaxies, where central LIER emission is spatially extended, but accompanied by star formation at larger galactocentric distances, and `extended LIER' (eLIER) galaxies, where LIER emission is extended throughout the whole galaxy. In eLIER and cLIER galaxies, LIER emission is associated with radially flat, low H$\alpha$ equivalent width of line emission ($

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SDSS IV MaNGA – spatially resolved diagnostic diagrams: a proof that many galaxies are LIERs

The Very Large Array Sky Survey (VLASS) is a synoptic, all-sky radio sky survey with a unique combination of high angular resolution (≈2.5\"), sensitivity (a 1σ goal of 70 μJy/beam in the coadded data), full linear Stokes polarimetry, time domain coverage, and wide bandwidth (2-4 GHz). The first observations began in September 2017, and observing for the survey will finish in 2024. VLASS will use approximately 5500 hours of time on the Karl G. Jansky Very Large Array (VLA) to cover the whole sky visible to the VLA (Declination > −40∘), a total of 33,885 deg^2. The data will be taken in three epochs to allow the discovery of variable and transient radio sources. The survey is designed to engage radio astronomy experts, multi-wavelength astronomers, and citizen scientists alike. By utilizing an \"on the fly\" interferometry mode, the observing overheads are much reduced compared to a conventional pointed survey. In this paper, we present the science case and observational strategy for the survey, and also results from early survey observations.

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The Karl G. Jansky Very Large Array Sky Survey (VLASS). Science Case and Survey Design

Hierarchical assembly models predict a population of supermassive black hole (SMBH) binaries. These are not resolvable by direct imaging but may be detectable via periodic variability (or nanohertz frequency gravitational waves). Following our detection of a 5.2-year periodic signal in the quasar PG 1302−102, we present a novel analysis of the optical variability of 243 500 known spectroscopically confirmed quasars using data from the Catalina Real-time Transient Survey (CRTS) to look for close (<0.1 pc) SMBH systems. Looking for a strong Keplerian periodic signal with at least 1.5 cycles over a baseline of nine years, we find a sample of 111 candidate objects. This is in conservative agreement with theoretical predictions from models of binary SMBH populations. Simulated data sets, assuming stochastic variability, also produce no equivalent candidates implying a low likelihood of spurious detections. The periodicity seen is likely attributable to either jet precession, warped accretion discs or periodic accretion associated with a close SMBH binary system. We also consider how other SMBH binary candidates in the literature appear in CRTS data and show that none of these are equivalent to the identified objects. Finally, the distribution of objects found is consistent with that expected from a gravitational-wave-driven population. This implies that circumbinary gas is present at small orbital radii and is being perturbed by the black holes. None of the sources is expected to merge within at least the next century. This study opens a new unique window to study a population of close SMBH binaries that must exist according to our current understanding of galaxy and SMBH evolution.

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A systematic search for close supermassive black hole binaries in the Catalina Real-time Transient Survey

The optical spectra of 3,896 Seyfert~1 (Sy1) galaxies detected with WISE at z < 0.4 were analyzed for evidence of outflows. In 37% of the Sy1s the outflows appear as broad, blue-shifted, of the [OIII]5007, with a mean maximum velocity V_max ~1014 km/s$, consistent with AGN winds. For each Sy1 we deduced that black hole (BH) mass, bolometric luminosity, Eddington ratio and power-law index of the continuum, which we compared with the star formation rate (SFR) and host morphology. Having separated our sample in two spectroscopic subgroups, Sy1s with only broad Balmer lines (Sy1B) and with both narrow and broad (Sy1N) lines and distinguishing those that show as outflow (Sy1Bw and Sy1Nw), we report the following differences: 1) the BH mass is systematically higher and the power-law steeper in the Sy1B-Sy1Bw than in the Sy1N-Sy1Nw, 2) V_max is higher in the Sy1Bw than in the Sy1Nw, correlated in both groups with the BH mass and bolometric luminosity, 3) the Eddington ratio and SFR are higher in the Sy1 with outflows, and 4) the specific star formation rates (sSFRs) of the Sy1s are normal for their morphology and mass; typical of early-type spiral galaxies in the green valley, far from the quenched regime. From these results we conclude that in Sy1s AGN winds are triggered by higher accretion rates and probably radiatively launched, and there is no clear evidence of an effect on the star formation.

The ubiquity of AGN winds in Seyfert 1 galaxies at low redshift

A sample of 229618 narrow emission-line galaxies is used to establish two new unambiguous types of evidence for supermassive black holes at the center of their nuclei: (1) the Seyfert 2 galaxies and LINERs follow the same characteristic power law relating the luminosity of the ionized flux with that of the continuum; (2) both show the highest concentration of mass at their center, independent of the morphology of the galaxy, consistent with higher binding energies. The full width at half maximum is shown to be related with the mass concentration, suggesting that the kinetic energy of the gas in AGNs has a gravitational origin. Within the standard accretion model, transition-type objects, Seyfert 2 galaxies and LINERs represent AGNs forming supermassive black holes on different mass-scales, or they could be related through an evolutionary process, the LINERs representing the end product of this evolution.

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Evidence of Supermassive Black Holes in Narrow Emission Line Galaxies

Using a sample of 229618 narrow emission-line galaxies, we have determined the normal star formation histories (SFHs) for galaxies with different activity types: star forming galaxies (SFGs), transition type objects (TOs), Seyfert 2s (Sy2s) and LINERs. We find that the variation of the SFH with the activity type is explained by the mass of the galaxies and the importance of their bulge: the LINERs reside in massive early-type galaxies, the Sy2s and TOs are hosted by intermediate mass galaxies with intermediate morphological types, and the SFGs are found in lower mass late-type spirals. Except for the Sy2s, the more massive galaxies formed the bulk of their stars more rapidly than the less massive ones. The Sy2s formed their stars more slowly and show presently an excess in star formation. We have also found that the maximum in star formation rate in the past increases with the virial mass within the aperture (VMA), the VMA increasing from the SFGs to the TOs, to the Sy2s, culminating in the LINERs. This correlation suggests that the bulges and the supermassive black holes at the center of galaxies grow in parallel, in good agreement with the M(BH)-sigma relation.

What do the Star Formation Histories of Galaxies tell us about the Starburst-AGN connection?

Using the largest sample of narrow emission line galaxies available so far, we show that their spectral characteristics are correlated with different physical parameters, like the chemical abundances, the morphologies, the masses of the bulge and the mean stellar age of the stellar populations of the host galaxies. It suggests that the spectral variations observed in standard spectroscopic diagnostic diagrams are not due solely to variations of ionization parameters or structures but reflect also the chemical evolution of the galaxies, which in turn can be explained by different galaxy formation processes.

The Chemical Evolution of Narrow Emission Line Galaxies: the Key to their Formation Processes

We present preliminary results of applying a neighbour search code to a large sample of galaxies drawn from the Sloan Digitial Sky Survey (SDSS). We draw our sample of target galaxies from the spectroscopic catalogue of the SDSS, which has redshift measurements for all its $\sim8\times10^5$ galaxies. We count the neighbours from the photometric catalogue of the SDSS, which is a flux-limited catalogue that has a photometric redshift estimation for all its $\sim2\times10^8$ galaxies. The code counts the number (N) of galaxies within a given 3D-distance from the target galaxy, using a database manager and a simple decision tree. The 3D-distance is composed of a 2D projected distance on the sky and a radial component, which is the difference between the spectroscopic target redshift and the photometric redshift of the "neighbour" galaxies. As we keep the search volume constant throughout the sample, N is a proxy for the number density of galaxies around the target galaxies. We also present an analysis of the preliminary results, showing the relation between N, the inferred morphology and the dominant activity type of the target galaxies, as well as the relation between N and the star formation history of the target galaxies.

Juan Pablo Torres-Papaqui

Papers

The ubiquity of AGN winds in Seyfert 1 galaxies at low redshift

Evidence of Supermassive Black Holes in Narrow Emission Line Galaxies

What do the Star Formation Histories of Galaxies tell us about the Starburst-AGN connection?

The Chemical Evolution of Narrow Emission Line Galaxies: the Key to their Formation Processes

A neighbor Search Code for Galaxies - Preliminary Results