We present an overview of a new integral field spectroscopic survey called MaNGA (Mapping Nearby Galaxies at Apache Point Observatory), one of three core programs in the fourth-generation Sloan Digital Sky Survey (SDSS-IV) that began on 2014 July 1. MaNGA will investigate the internal kinematic structure and composition of gas and stars in an unprecedented sample of 10,000 nearby galaxies. We summarize essential characteristics of the instrument and survey design in the context of MaNGA's key science goals and present prototype observations to demonstrate MaNGA's scientific potential. MaNGA employs dithered observations with 17 fiber-bundle integral field units that vary in diameter from 12 (19 fibers) to 32 (127 fibers). Two dual-channel spectrographs provide simultaneous wavelength coverage over 3600-10300Å at R∼2000. With a typical integration time of 3 hr, MaNGA reaches a target r-band signal-to-noise ratio of 4-8 (Å −1 per 2 fiber) at 23 AB mag arcsec −2 , which is typical for the outskirts of MaNGA galaxies. Targets are selected with M * 10 9 M using SDSS-I redshifts and i-band luminosity to achieve uniform radial coverage in terms of the effective radius, an approximately flat distribution in stellar mass, and a sample spanning a wide range of environments. Analysis of our prototype observations demonstrates MaNGA's ability to probe gas ionization, shed light on recent star formation and quenching, enable dynamical modeling, decompose constituent components, and map the composition of stellar populations. MaNGA's spatially resolved spectra will enable an unprecedented study of the astrophysics of nearby galaxies in the coming 6 yr.

We present ground-based and Swift photometric and spectroscopic observations of the tidal disruption event (TDE) ASASSN-15oi, discovered at the center of 2MASX J20390918-3045201 (d 216 Mpc) by the All-Sky Automated Survey for SuperNovae (ASAS-SN). The source peaked at a bolometric luminosity of L 1.3 × 10 44 ergs s −1 and radiated a total energy of E 6.6 × 10 50 ergs over the first ∼ 3.5 months of observations. The early optical/UV emission of the source can be fit by a blackbody with temperature increasing from T ∼ 2×10 4 K to T ∼ 4×10 4 K while the luminosity declines from L 1.3 × 10 44 ergs s −1 to L 2.3 × 10 43 ergs s −1 , requiring the photosphere to be shrinking rapidly. The optical/UV luminosity decline during this period is most consistent with an exponential decline, L ∝ e −(t−t0)/τ , with τ 46.5 days for t 0 57241.6 (MJD), while a power-law decline of L ∝ (t − t 0 ) −α with t 0 57212.3 and α = 1.62 provides a moderately worse fit. ASASSN-15oi also exhibits roughly constant soft X-ray emission that is significantly weaker than the optical/UV emission. Spectra of the source show broad helium emission lines and strong blue continuum emission in early epochs, although these features fade rapidly and are not present ∼ 3 months after discovery. The early spectroscopic features and color evolution of ASASSN-15oi are consistent with a TDE, but the rapid spectral evolution is unique among optically-selected TDEs.

The individual star formation histories of bulges and discs of lenticular (S0) galaxies can provide information on the processes involved in the quenching of their star formation and subsequent transformation from spirals. In order to study this transformation in dense environments, we have decomposed long-slit spectroscopic observations of a sample of 21 S0s from the Virgo Cluster to produce one-dimensional spectra representing purely the bulge and disc light for each galaxy. Analysis of the Lick indices within these spectra reveals that the bulges contain consistently younger and more metal-rich stellar populations than their surrounding discs, implying that the final episode of star formation within S0s occurs in their central regions. Analysis of the α-element abundances in these components further presents a picture in which the final episode of star formation in the bulge is fueled using gas that has previously been chemically enriched in the disc, indicating the sequence of events in the transformation of these galaxies. Systems in which star formation in the disk was spread over a longer period contain bulges in which the final episode of star formation occurred more recently, as one might expect for an approximately coeval population in which the transformation from spiral to S0 occurred at different times. With data of this quality and the new analysis method deployed here, we can begin to describe this process in a quantitative manner for the first time.

A new method for spectroscopic bulge–disc decomposition is presented, in which the spatial light profile in a two‐dimensional spectrum is decomposed wavelength by wavelength into bulge and disc components, allowing separate one‐dimensional spectra for each component to be constructed. This method has been applied to observations of a sample of nine lenticular galaxies (S0s) in the Fornax Cluster in order to obtain clean high‐quality spectra of their individual bulge and disc components. So far this decomposition has only been fully successful when applied to galaxies with clean light profiles, without contamination from dust lanes, etc. This has consequently limited the number of galaxies that could be separated into bulge and disc components. The Lick index stellar population analysis of the component spectra reveals that in those galaxies where the bulge and disc could be distinguished, the bulges have systematically higher metallicities and younger stellar populations than the discs. This correlation is consistent with a picture in which S0 formation comprises the shutting down of star formation in the disc accompanied by a final burst of star formation in the bulge. Similarly, a trend was found to exist whereby galaxies with younger stellar populations have higher metallicities. The variation in spatial‐fit parameters with wavelength also allows us to measure approximate colour gradients in the individual components. Such gradients were detected separately in both bulges and discs, in the sense that redder light is systematically more centrally concentrated in all components. However, a search for radial variations in the absorption line strengths determined for the individual components revealed that, although they can be sensitively detected where present, they are absent from the vast majority of S0 discs and bulges. The absence of gradients in line indices for most galaxies implies that the colour gradient cannot be attributed to age or metallicity variations and is therefore most likely associated with varying degrees of obscuration by dust.

Here we demonstrate that phosphorylation of the sphingosine 1-phosphate (SSP) receptor "endothelial differentiation gene 1" (EDG1 or S1P 1 ) receptor is increased in response to either SSP or phorbol 12-myristate 13-acetate (PMA) exposure but not lysophosphatidic acid. Phosphoamino acid analysis demonstrated that SSP stimulated the accumulation of phosphoserine and phosphothreonine but not phosphotyrosine. An inhibitor of PMA-stimulated EDG1 phosphorylation failed to block SSP-stimulated phosphorylation. Additionally, removal of 12 amino acids from the carboxyl terminus of EDG1 specifically reduced SSP-but not PMA-stimulated phosphorylation, suggesting that SSP and PMA increase EDG1 phosphorylation via distinct mechanisms. In vitro assays revealed that G-protein-coupled receptor kinase 2 may be at least partially responsible for SSP-stimulated EDG1 phosphorylation observed in intact cells. In addition, phosphorylation by PMA and SSP were associated with a loss of EDG1 from the cell surface by distinct mechanisms. Removal of 12 residues from the carboxyl terminus of EDG1 completely inhibited SSPmediated internalization, suggesting that this domain dictates susceptibility to receptor internalization while retaining sensitivity to SSP-stimulated phosphorylation. Thus, we conclude that (a) EDG1 phosphorylation and internalization are controlled via independent mechanisms by agonist occupation of the receptor and protein kinase C activation, and (b) although determinants within the receptor's carboxyl-terminal tail conferring EDG1 sensitivity to agonist-mediated internalization and G-protein-coupled receptor kinase phosphorylation exhibit a degree of overlap, the two phenomena are separable.