In this work, we show how the stellar mass (M-*) of galaxies affects the 3 < z < 4.6 Ly alpha equivalent width (EW) distribution. To this end, we design a sample of 629 galaxies in the M-* range 7.6 < logM(*)/M-circle dot < 10.6 from the 3D-HST/CANDELS survey. We perform spectroscopic observations of this sample using the Michigan/Magellan Fiber System, allowing us to measure Ly alpha fluxes and use 3D-HST/CANDELS ancillary data. In order to study the Ly alpha EW distribution dependence on M-*, we split the whole sample in three stellar mass bins. We find that, in all bins, the distribution is best represented by an exponential profile of the form dN(M-*)/dEW = W-0(M-*)(-1)A(M-*)e(-EW/W0(M*)). Through a Bayesian analysis, we confirm that lower M-* galaxies have higher Lya EWs. We also find that the fraction A of galaxies featuring emission and the e-folding scale W-0 of the distribution anti-correlate with M-*, recovering expressions of the forms A(M-*) = -0.26(.13)logM(*)/M-circle dot + 3.01(1.2) and W-0(M-*) = -15.6(3.5)logM(*)/M-circle dot + 166(34). These results are crucial for proper interpretation of Ly alpha emission trends reported in the literature that may be affected by strong M-* selection biases.

NGC 1042 is a late-type bulgeless disk galaxy that hosts low-luminosity active galactic nuclei (AGNs) coincident with a massive nuclear star cluster. In this paper, we present the integral field spectroscopy studies of this galaxy, based on the data obtained with the Mitchell spectrograph on the 2.7 m Harlan J. Smith telescope. In the central 100-300 pc region of NGC 1042, we find a circumnuclear ring structure of gas with enhanced ionization, which we suggest is mainly induced by shocks. Combining this with the harmonic decomposition analysis of the velocity field of the ionized gas, we propose that the shocked gas is the result of gas inflow driven by the inner spiral arms. The inflow velocity is similar to 32 +/- 10 km s(-1), and the estimated mass-inflow rate is similar to 1.1 +/- 0.3 x 10(-3) M-circle dot yr(-1). The mass-inflow rate is about one hundred times the black hole's mass-accretion rate (similar to 1.4 x 10(-5) M-circle dot yr(-1)) and slightly larger than the star-formation rate in the nuclear star cluster (7.94 x 10(-4) M-circle dot yr(-1)), implying that the inflow material is enough to feed both the AGN activity and star formation in the nuclear star cluster. Our study highlights that secular evolution can be important in late-type unbarred galaxies like NGC 1042.

We present a study of the excitation conditions and metallicity of ionized gas (Z(gas)) in eight nearby barred and unbarred spiral galaxies from the VIRUS-P Exploration of Nearby Galaxies (VENGA) survey, which provides high spatial sampling and resolution (median similar to 387 pc), large coverage from the bulge to outer disc, broad wavelength range (3600-6800 angstrom), and medium spectral resolution (similar to 120 km s(-1) at 5000 angstrom). Our results are: (1) We present high resolution gas excitation maps to differentiate between regions with excitation typical of Seyfert, LINER, or recent star formation. We find LINER-type excitation at large distances (3-10 kpc) from the centre, and associate this excitation with diffuse ionized gas (DIG). (2) After excluding spaxels dominated by Seyfert, LINER, or DIG, we produce maps with the best spatial resolution and sampling to date of the ionization parameter q, star formation rate, and Z(gas) using common strong line diagnostics. We find that isolated barred and unbarred spirals exhibit similarly shallow Z(gas) profiles from the inner kpc out to large radii (7-10 kpc or 0.5-1.0 R-25). This implies that if profiles had steeper gradients at earlier epochs, then the presentday bar is not the primary driver flattening gradients over time. This result contradicts earlier claims, but agrees with recent IFU studies. (3) The Z(gas) gradients in our z similar to 0 massive spirals are markedly shallower, by similar to 0.2 dex kpc(-1), than published gradients for lensed lower mass galaxies at z similar to 1.5-2.0. Cosmologically motivated hydrodynamical simulations best match this inferred evolution, but the match is sensitive to adopted stellar feedback prescriptions.

The cloud-scale density, velocity dispersion, and gravitational boundedness of the interstellar medium (ISM) vary within and among galaxies. In turbulent models, these properties play key roles in the ability of gas to form stars. New high-fidelity, high-resolution surveys offer the prospect to measure these quantities across galaxies. We present a simple approach to make such measurements and to test hypotheses that link small-scale gas structure to star formation and galactic environment. Our calculations capture the key physics of the Larson scaling relations, and we show good correspondence between our approach and a traditional "cloud properties" treatment. However, we argue that our method is preferable in many cases because of its simple, reproducible characterization of all emission. Using, low-J (CO)-C-12 data from recent surveys, we characterize the molecular ISM at 60 pc resolution in the Antennae, the Large Magellanic Cloud (LMC), M31, M33, M51, and M74. We report the distributions of surface density, velocity dispersion, and gravitational boundedness at 60 pc scales and show galaxy-to-galaxy and intragalaxy variations in each. The distribution of flux as a function of surface density appears roughly lognormal with a 1 sigma width of similar to 0.3 dex, though the center of this distribution varies from galaxy to galaxy. The 60 pc resolution line width and molecular gas surface density correlate well, which is a fundamental behavior expected for virialized or free-falling gas. Varying the measurement scale for the LMC and M31, we show that the molecular ISM has higher surface densities, lower line widths, and more self-gravity at smaller scales.

The Visible Integral-field Replicable Unit Spectrograph (VIRUS) consists of 156 identical spectrographs (arrayed as 78 pairs) fed by 35,000 fibers, each 1.5 arcsec diameter, at the focus of the upgraded 10 m Hobby-Eberly Telescope (HET). VIRUS has a fixed bandpass of 350-550 nm and resolving power R similar to 700. VIRUS is the first example of industrial-scale replication applied to optical astronomy and is capable of surveying large areas of sky, spectrally. The VIRUS concept offers significant savings of engineering effort, cost, and schedule when compared to traditional instruments.

We revisit the evolution of the mass-metallicity relation of low- and high-redshift galaxies by using a sample of local analogs of high-redshift galaxies. These analogs share the same location of the UV-selected star-forming galaxies at z similar to 2 on the [O III]lambda 5007/H beta versus [N II]lambda 6584/H alpha nebular emission-line diagnostic (or BPT) diagram. Their physical properties closely resemble those in z similar to 2 UV-selected star-forming galaxies being characterized, in particular, by high ionization parameters (log q approximate to 7.9) and high electron densities (n(e) approximate to 100 cm(-3)). With the full set of well-detected rest-frame optical diagnostic lines, we measure the gasphase oxygen abundance in the SDSS galaxies and these local analogs using the empirical relations and the photoionization models. We find that the metallicity difference between the SDSS galaxies and our local analogs in the 8.5 < log(M-* M-Theta) < 9.0 stellar mass bin varies from -0.09 to 0.39 dex, depending on strong-line metallicity measurement methods. Due to this discrepancy, the evolution of mass-metallicity should be used to compare with the cosmological simulations with caution. We use the [S II]/H alpha and [O I]/H alpha BPT diagram to reduce the potential AGN and shock contamination in our local analogs. We find that the AGN/shock influences are negligible on the metallicity estimation.

Distance uncertainties plague our understanding of the physical scales relevant to the physics of star formation in extragalactic studies. The planetary nebulae luminosity function (PNLF) is one of very few techniques that can provide distance estimates to within similar to 10%; however, it requires a planetary nebula (PN) sample that is uncontaminated by other ionizing sources. We employ optical integral field unit spectroscopy using the Multi-Unit Spectroscopic Explorer on the Very Large Telescope to measure [O III] line fluxes for sources unresolved on 50 pc scales within the central star-forming galaxy disk of NGC 628. We use diagnostic line ratios to identify 62 PNe, 30 supernova remnants, and 87 H II regions within our fields. Using the 36 brightest PNe, we determine a new PNLF distance modulus of 29.91(-0.13)(+0.08) mag (9.59(-0.57)(+0.35) Mpc), which is in good agreement with literature values, but significantly larger than the previously reported PNLF distance. We are able to explain the discrepancy and recover the previous result when we reintroduce SNR contaminants to our sample. This demonstrates the power of full spectral information over narrowband imaging in isolating PNe. Given our limited spatial coverage within the Galaxy, we show that this technique can be used to refine distance estimates, even when IFU observations cover only a fraction of a galaxy disk.

We present an exhaustive census of Lyman alpha (Ly alpha) emission in the general galaxy population at 3 < z < 4.6. We use the Michigan/Magellan Fiber System (M2FS) spectrograph to study a stellar mass (M-*) selected sample of 625 galaxies homogeneously distributed in the range 7.6 < logM(*)/M-circle dot < 10.6. Our sample is selected from the 3D-HST/CANDELS survey, which provides the complementary data to estimate Ly alpha equivalent widths (W-Ly alpha) and escape fractions (f(esc)) for our galaxies. We find both quantities to anti-correlate with M-*, star formation rate (SFR), UV luminosity, and UV slope (beta). We then model the WLya distribution as a function of M-UV and beta using a Bayesian approach. Based on our model and matching the properties of typical Lyman break galaxy (LBG) selections, we conclude that theW(Ly alpha) distribution in such samples is heavily dependent on the limiting M-UV of the survey. Regarding narrowband surveys, we find their W-Ly alpha selections to bias samples toward low M-*, while their line-flux limitations preferentially leave out low-SFR galaxies. We can also use our model to predict the fraction of Ly alpha-emitting LBGs at 4 <= z <= 7. We show that reported drops in the Lya fraction at z >= 6, usually attributed to the rapidly increasing neutral gas fraction of the universe, can also be explained by survey M-UV incompleteness. This result does not dismiss reionization occurring at z similar to 7, but highlights that current data is not inconsistent with this process taking place at z > 7.

AGN feedback is invoked as one of the most relevant mechanisms that shape the evolution of galaxies. Our goal is to understand the interplay between AGN feedback and the interstellar medium in M 51, a nearby spiral galaxy with a modest AGN and a kpc-scale radio jet expanding through the disc of the galaxy. For this purpose, we combine molecular gas observations in the CO(1-0) and HCN(1-0) lines from the Plateau de Bure interferometer with archival radio, X-ray, and optical data. We show that there is a significant scarcity of CO emission in the ionisation cone, while molecular gas emission tends to accumulate towards the edges of the cone. The distribution and kinematics of CO and HCN line emission reveal AGN feedback effects out to r similar to 500 pc, covering the whole extent of the radio jet, with complex kinematics in the molecular gas which displays strong local variations. We propose that this is the result of the almost coplanar jet pushing on molecular gas in different directions as it expands; the effects are more pronounced in HCN than in CO emission, probably as the result of radiative shocks. Following previous interpretation of the redshifted molecular line in the central 5 '' as caused by a molecular outflow, we estimate the outflow rates to be (M) over dot(H2) similar to 0.9 M-circle dot/yr and (M) over dot(dense) similar to 0.6 M-circle dot/yr, which are comparable to the molecular inflow rates (similar to 1 M-circle dot/yr); gas inflow and AGN feedback could be mutually regulated processes. The agreement with findings in other nearby radio galaxies suggests that this is not an isolated case, and is probably the paradigm of AGN feedback through radio jets, at least for galaxies hosting low-luminosity active nuclei.