We describe the design, manufacture, and performance of bare-fiber integral field units (IFUs) for the SDSS-IV survey MaNGA (Mapping Nearby Galaxies at APO) on the the Sloan 2.5 m telescope at Apache Point Observatory (APO). MaNGA is a luminosity-selected integral-field spectroscopic survey of 10 4 local galaxies covering 360-1030 nm at R ∼ 2200. The IFUs have hexagonal dense packing of fibers with packing regularity of 3 µm (RMS), and throughput of 96±0.5% from 350 nm to 1 µm in the lab. Their sizes range from 19 to 127 fibers (3-7 hexagonal layers) using Polymicro FBP 120:132:150 µm core:clad:buffer fibers to reach a fill fraction of 56%. High throughput (and low focal-ratio degradation) is achieved by maintaining the fiber cladding and buffer intact, ensuring excellent surface polish, and applying a multi-layer AR coating of the input and output surfaces. In operations on-sky, the IFUs show only an additional 2.3% FRD-related variability in throughput despite repeated mechanical stressing during plate plugging (however other losses are present). The IFUs achieve on-sky throughput 5% above the single-fiber feeds used in SDSS-III/BOSS, attributable to equivalent performance compared to single fibers and additional gains from the AR coating. The manufacturing process is geared toward mass-production of high-multiplex systems. The low-stress process involves a precision ferrule with hexagonal inner shape designed to lead inserted fibers to settle in a dense hexagonal pattern. The ferrule inner diameter is tapered at progressively shallower angles toward its tip and the final 2 mm are straight and only a few micron larger than necessary to hold the desired number of fibers. Our IFU manufacturing process scales easily to accommodate other fiber sizes and can produce IFUs with substantially larger fiber counts. To assure quality, automated testing in a simple and inexpensive system enables complete characterization of throughput and fiber metrology. Future applications include larger IFUs, higher fill-factors with stripped buffer, de-cladding, and lenslet coupling.

Classi cation of galaxy spectral energy distributions in terms of orthogonal basis functions provides an objective means of estimating the number of signi cant spectral components that comprise a particular galaxy type. We apply the Karhunen-Lo eve transform to derive a spectral eigensystem from a sample of ten galaxy spectral energy distributions. These spectra cover a wavelength range of 1200 A to 1 m and galaxy morphologies from elliptical to starburst. We nd that the distribution of spectral types can be fully described by the rst two eigenvectors (or eigenspectra). The derived eigenbasis is a ected by the normalization of the original spectral energy distributions. We investigate di erent normalization and weighting schemes, including weighting to the same bolometric magnitude and weighting by the observed distribution of morphological types. Projecting the spectral energy distributions on to their eigenspectra we nd that the coe cients de ne a simple spectral classi cation scheme. The galaxy spectral types can then be described in terms of a one parameter family (the angle in the plane of the rst two eigenvectors). We nd a strong correlation in the mean between our spectral classi cations and those determined from published morphological classi cations.

A re ned sample of 64 variable objects with stellar image structure has been identi ed in SA 57 to B 22:5, over a time baseline of 15 years, sampled at 11 distinct epochs. The photometric data typically have a root-mean-square error at B = 22 of only 0.05 mag. Thirty-ve quasars in this eld have already been spectroscopically con rmed, 34 of which are among the sample of variables. Of the other variables, 6 are known spectroscopically to be stars, 10 additional objects are stars based on reliable detection of proper motion, and 1 is spectroscopically a narrow-emission-line galaxy. Of the 13 remaining variables, it is argued that they are a mixture of distant halo subdwarfs and quasars with star-like colors. We compute the ensemble average structure function and autocorrelation function from the light curves in the respective quasar rest-frames, which are used to investigate the general dependences on apparent magnitude, absolute magnitude, and redshift.

Galaxies grow through both internal and external processes. In about 10% of nearby red galaxies with little star formation, gas and stars are counter-rotating, demonstrating the importance of external gas acquisition in these galaxies. However, systematic studies of such phenomena in blue, star-forming galaxies are rare, leaving uncertain the role of external gas acquisition in driving evolution of blue galaxies. Here, based on new measurements with integral field spectroscopy of a large representative galaxy sample, we find an appreciable fraction of counter-rotators among blue galaxies (9 out of 489 galaxies). The central regions of blue counter-rotators show younger stellar populations and more intense, ongoing star formation than their outer parts, indicating ongoing growth of the central regions. The result offers observational evidence that the acquisition of external gas in blue galaxies is possible; the interaction with pre-existing gas funnels the gas into nuclear regions (<1 kpc) to form new stars.

Luminous Compact Blue Galaxies (LCBGs) are an extreme star-bursting population of galaxies that were far more common at earlier epochs than today. Based on spectroscopic and photometric measurements of LCBGs in massive (M > 10 15 M ), intermediate redshift (0.5 < z < 0.9) galaxy clusters, we present their rest-frame properties including star-formation rate, dynamical mass, size, luminosity, and metallicity. The appearance of these small, compact galaxies in clusters at intermediate redshift helps explain the observed redshift evolution in the size-luminosity relationship among cluster galaxies. In addition, we find the rest-frame properties of LCBGs appearing in galaxy clusters are indistinguishable from field LCBGs at the same redshift. Up to 35% of the LCBGs show significant discrepancies between optical and infrared indicators of star formation, suggesting that star formation occurs in obscured regions. Nonetheless, the star formation for LCBGs shows a decrease toward the center of the galaxy clusters. Based on their position and velocity, we estimate that up to 10% of cluster LCBGs are likely to merge with another cluster galaxy. Finally, the observed properties and distributions of the LCBGs in these clusters lead us to conclude that we are witnessing the quenching of the progenitors of dwarf elliptical galaxies that dominate the number density of present-epoch galaxy clusters.