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 describe the Sloan

We describe the results of an extremely deep, 0.28 deg 2 survey for z ¼ 3:1 Ly emission-line galaxies in the Extended Chandra Deep FieldYSouth. By using a narrowband 5000 8 filter and complementary broadband photometry from the MUSYC survey, we identify a statistically complete sample of 162 galaxies with monochromatic fluxes brighter than 1:5 ; 10 À17 ergs cm À2 s À1 and observer's frame equivalent widths greater than 80 8. We show that the equivalent width distribution of these objects follows an exponential with a rest-frame scale length of w 0 ¼ 76In addition, we show that in the emission line, the luminosity function of Ly galaxies has a faint-end power-law slope of ¼ À1:49 þ0:45 À0:34 , a bright-end cutoff of log L Ã ¼ 42:64 þ0:26 À0:15 , and a space density above our detection thresholds of (1:46 AE 0:12) ; 10 À3 h 3 70 galaxies Mpc À3 . Finally, by comparing the emission-line and continuum properties of the Ly emitters, we show that the star formation rates derived from Ly are $3 times lower than those inferred from the rest-frame UV continuum. We use this offset to deduce the existence of a small amount of internal extinction within the host galaxies. This extinction, coupled with the lack of extremely high equivalent width emitters, argues that these galaxies are not primordial Population III objects, although they are young and relatively chemically unevolved.

This paper documents the 16th data release (DR16) from the Sloan Digital Sky Surveys (SDSS), the fourth and penultimate from the fourth phase (SDSS-IV). This is the first release of data from the Southern Hemisphere survey of the Apache Point Observatory Galactic Evolution Experiment 2 (APOGEE-2); new data from APOGEE-2 North are also included. DR16 is also notable as the final data release for the main cosmological program of the Extended Baryon Oscillation Spectroscopic Survey (eBOSS), and all raw and reduced spectra from that project are released here. DR16 also includes all the data from the Time Domain Spectroscopic Survey and new data from the SPectroscopic IDentification of ERosita Survey programs, both of which were co-observed on eBOSS plates. DR16 has no new data from the Mapping Nearby Galaxies at Apache Point Observatory (MaNGA) survey (or the MaNGA Stellar Library “MaStar”). We also preview future SDSS-V operations (due to start in 2020), and summarize plans for the final SDSS-IV data release (DR17).

We studied the clustering properties and multiwavelength spectral energy distributions of a complete sample of 162 Ly-emitting (LAE) galaxies at z ' 3:1 discovered in deep narrowband MUSYC imaging of the Extended Chandra Deep Field-South. LAEs were selected to have observed frame equivalent widths >80 8 and emission line fluxes >1:5 ; 10 À17 ergs cm À2 s À1. Only 1% of our LAE sample appears to host AGNs. The LAEs exhibit a moderate spatial correlation length of r 0 ¼ 3:6 þ0:8 À1:0 Mpc, corresponding to a bias factor b ¼ 1:7 þ0:3 À0:4 , which implies median dark matter halo masses of log 10 M med ¼ 10:9 þ0:5 À0:9 M . Comparing the number density of LAEs, 1:5 AE 0:3 ; 10 À3 Mpc À3, with the number density of these halos finds a mean halo occupation $1%Y10%. The evolution of galaxy bias with redshift implies that most z ¼ 3:1 LAEs evolve into present-day galaxies with L < 2:5L Ã , whereas other z > 3 galaxy populations typically evolve into more massive galaxies. Halo merger trees show that z ¼ 0 descendants occupy halos with a wide range of masses, with a median descendant mass close to that of L Ã . Only 30% of LAEs have sufficient stellar mass (>$3 ;

The fourth generation of the Sloan

We measure the velocity dispersion, σ, and surface density, Σ, of the molecular gas in nearby galaxies from CO spectral line cubes with spatial resolution 45-120 pc, matched to the size of individual giant molecular clouds. Combining 11 galaxies from the PHANGS-ALMA survey with 4 targets from the literature, we characterize ∼ 30, 000 independent sightlines where CO is detected at good significance. Σ and σ show a strong positive correlation, with the best-fit power law slope close to the expected value for resolved, self-gravitating clouds. This indicates only weak variation in the virial parameter α vir ∝ σ 2 /Σ, which is ∼1.5-3.0 for most galaxies. We do, however, observe enormous variation in the internal turbulent pressure P turb ∝ Σ σ 2 , which spans ∼5 dex across our sample. We find Σ, σ, and P turb to be systematically larger in more massive galaxies. The same quantities appear enhanced in the central kpc of strongly barred galaxies relative to their disks. Based on sensitive maps of M31 and M33, the slope of the σ-Σ relation flattens at Σ 10 M pc −2 , leading to high σ for a given Σ and high apparent α vir . This echoes results found in the Milky Way, and likely originates from a combination of lower beam filling factors and a stronger influence of local environment on the dynamical state of molecular gas in the low density regime.

No abstract