We present mosaicked long-slit spectral maps of 18 nearby Active Galactic Nuclei (AGNs), 2 LINERs, and 4 star-forming galaxies. With the resulting data cubes taken using the Kast dual spectrograph on the 3 m Shane telescope of the Lick Observatory, we measure the aperture effects on the spectroscopic classification of AGNs. With more starlight included in a larger aperture, the nuclear spectrum that is Seyfert-like may become contaminated. We generated standard spectroscopic classification diagrams in different observing apertures. These show quantitatively how the ensemble of Seyferts migrates toward the H $\scriptsize{\textrm{II}}$ region classification when being observed with increasing aperture sizes. But the effect ranges widely in individual active galaxies. Some of the less luminous Seyferts shfit by a large amount, while some other barely move or even shift in different directions. We find that those Seyfert galaxies with the fraction of nuclear H$\alpha$ emission lower than 0.2 of the host galaxy, 2-10 keV hard X-ray luminosity lower than $10^{43}$ erg s$^{-1}$, and the observed nuclear [O $\scriptsize{\textrm{III}}$] luminosity lower than $10^{40.5}$ erg s$^{-1}$, are more likely to change activity classification type when the entire host galaxy is included. Overall, 4 of our 24 galaxies (18 Seyferts) change their spectral activity classification type when observed with a very large aperture.

We used narrowband interference filters with the CCD imaging camera on the Nickel 1.0 meter telescope at Lick Observatory to observe 31 nearby (z < 0.03) Seyfert galaxies in the 12 {\mu}m Active Galaxy Sample. We obtained pure emission line images of each galaxy in order to separate H{\alpha} emission from the nucleus from that of the host galaxy. The extended H{\alpha} emission is expected to be powered by newly formed hot stars, and correlates well with other indicators of current star formation in these galaxies: 7.7 {\mu}m PAH, far-infrared, and radio luminosity. Relative to what would be expected from recent star formation, there is a 0.8 dex excess of radio emission in our Seyfert galaxies. The nuclear H{\alpha} luminosity is dominated by the AGN, and is correlated with the hard X-ray luminosity. There is an upward offset of 1 dex in this correlation for the Seyfert 1s due to a strong contribution from the Broad Line Region. We found a correlation between star formation rate and AGN luminosity. In spite of selection effects, we concluded that the absence of bright Seyfert nuclei in galaxies with low SFRs is real, albeit only weakly significant. We used our measured spatial distributions of H{\alpha} emission to determine what these Seyfert galaxies would look like when observed through fixed apertures at high redshifts. Although all would be detectable emission line galaxies at any redshift, most would appear dominated by HII region emission. Only the most luminous AGN would still be identified at z~0.3.

We present the first detailed study of the stellar populations of star-forming galaxies at z ∼ 1.5, which are selected by their [O II] emission line, detected in narrowband surveys. We identified ∼1300 [O II] emitters at z = 1.47 and z = 1.62 in the Subaru Deep Field with rest-frame equivalent widths (EWs) above 13 Å. Optical and near-infrared spectroscopic observations for ≈10% of our samples show that our separation of [O II] from [O III] emission-line galaxies in two-color space is 99% successful. We analyze the multi-wavelength properties of a subset of ∼1200 galaxies with the best photometry. They have average rest-frame EW of 45 Å, stellar mass of 3 × 109 M⊙, and stellar age of 100Myr. In addition, our spectral energy distribution (SED) fitting and broadband colors indicate that [O II] emitters span the full range of galaxy populations at z ∼ 1.5. We also find that 80% of [O II] emitters are also photometrically classified as "BX/BM" (UV) galaxies and/or the star-forming "BzK" (near-IR) galaxies. Our [O II] emission line survey produces a far more complete and somewhat deeper sample of z ∼ 1.5 galaxies than either the BX/BM or sBzK selection alone. We constructed average SEDs and find that higher [O II] EW galaxies have somewhat bluer continua. SED model-fitting shows that they have on average half the stellar mass of galaxies with lower [O II] EW. The observed [O II] luminosity is well correlated with the far-UV continuum with a logarithmic slope of 0.89 ± 0.22. The scatter of the [O II] luminosity against the far-UV continuum suggests that [O II] can be used as a star formation rate indicator with a reliability of 0.23 dex. © 2012. The American Astronomical Society. All rights reserved.

Upcoming space-based surveys such as Euclid and WFIRST-AFTA plan to measure baryonic acoustic oscillations in order to study dark energy. These surveys will use IR slitless grism spectroscopy to measure redshifts of a large number of galaxies over a significant redshift range. In this paper, we use the Wide Field Camera 3 Infrared Spectroscopic Parallel Survey (WISP) to estimate the expected number of Hα emitters observable by these future surveys. WISP is an ongoing Hubble Space Telescope slitless spectroscopic survey, covering the 0.8-1.65 μm wavelength range and allowing the detection of Hα emitters up to z ∼ 1.5 and [O iii] emitters to z ∼ 2.3. We derive the Hα-[O iii] bivariate line luminosity function (LLF) for WISP galaxies at z ∼ 1 using a maximum likelihood estimator that properly accounts for uncertainties in line luminosity measurements and we demonstrate how it can be used to derive the Hα luminosity function by exclusively fitting [O iii] data. Using the [O iii] LLF and assuming that the relation between Hα and [O iii] luminosity does not change significantly over the redshift range, we predict the Hα number counts at - the upper end of the redshift range of interest for future surveys. For the redshift range we expect ∼3000 galaxies deg-2 for a flux limit of 3 � 10-16 erg s-1 cm-2 (the proposed depth of the Euclid galaxy redshift survey) and ∼20,000 galaxies deg-2 for a flux limit of ∼10-16 erg s-1 cm-2 (the baseline depth of the WFIRST galaxy redshift survey).

We present near-infrared emission line counts and luminosity functions from the Hubble Space Telescope Wide Field Camera 3 Infrared Spectroscopic Parallels (WISP) program for 29 fields (0.037 deg2) observed using both the G102 and G141 grism. Altogether we identify 1048 emission line galaxies with observed equivalent widths greater than 40 Å, 467 of which have multiple detected emission lines. We use simulations to correct for significant (>20%) incompleteness introduced in part by the non-dithered, non-rotated nature of the grism parallels. The WISP survey is sensitive to fainter flux levels ((3-5) × 10-17 erg s-1 cm-2) than the future space near-infrared grism missions aimed at baryonic acoustic oscillation cosmology ((1-4) × 10-16 erg s-1 cm-2), allowing us to probe the fainter emission line galaxies that the shallower future surveys may miss. Cumulative number counts of 0.7 < z < 1.5 galaxies reach 10,000 deg-2 above an Hα flux of 2 × 10-16 erg s-1 cm-2. Hα-emitting galaxies with comparable [O III] flux are roughly five times less common than galaxies with just Hα emission at those flux levels. Galaxies with low Hα/[O III] ratios are very rare at the brighter fluxes that future near-infrared grism surveys will probe; our survey finds no galaxies with Hα/[O III] < 0.95 that have Hα flux greater than 3 × 10-16 erg s -1 cm-2. Our Hα luminosity function contains a comparable number density of faint line emitters to that found by the Near IR Camera and Multi-Object Spectrometer near-infrared grism surveys, but significantly fewer (factors of 3-4 less) high-luminosity emitters. We also find that our high-redshift (z = 0.9-1.5) counts are in agreement with the high-redshift (z = 1.47) narrowband Hα survey of HiZELS (Sobral et al.), while our lower redshift luminosity function (z = 0.3-0.9) falls slightly below their z = 0.84 result. The evolution in both the Hα luminosity function from z = 0.3-1.5 and the [O III] luminosity function from z = 0.7-2.3 is almost entirely in the L parameter, which steadily increases with redshift over those ranges. © 2013. The American Astronomical Society. All rights reserved..

We present the first robust measurement of the high redshift mass-metallicity (MZ) relation at 108 ≲ M/M ⊙ ≲ 1010, obtained by stacking spectra of 83 emission-line galaxies with secure redshifts between 1.3 ≲ z ≲ 2.3. For these redshifts, infrared grism spectroscopy with the Hubble Space Telescope Wide Field Camera 3 is sensitive to the R 23 metallicity diagnostic: ([O II] λλ3726, 3729 + [O III] λλ4959, 5007)/Hβ. Using spectra stacked in four mass quartiles, we find a MZ relation that declines significantly with decreasing mass, extending from 12+log(O/H) = 8.8 at M = 109.8 M ⊙, to 12+log(O/H) = 8.2 at M = 10 8.2 M ⊙. After correcting for systematic offsets between metallicity indicators, we compare our MZ relation to measurements from the stacked spectra of galaxies with M ≳ 109.5 M ⊙ and z ∼ 2.3. Within the statistical uncertainties, our MZ relation agrees with the z ∼ 2.3 result, particularly since our somewhat higher metallicities (by around 0.1 dex) are qualitatively consistent with the lower mean redshift (z = 1.76) of our sample. For the masses probed by our data, the MZ relation shows a steep slope which is suggestive of feedback from energy-driven winds, and a cosmological downsizing evolution where high mass galaxies reach the local MZ relation at earlier times. In addition, we show that our sample falls on an extrapolation of the star-forming main sequence (the SFR-M * relation) at this redshift. This result indicates that grism emission-line selected samples do not have preferentially high star formation rates (SFRs). Finally, we report no evidence for evolution of the mass-metallicity-SFR plane; our stack-averaged measurements show excellent agreement with the local relation. © 2013. The American Astronomical Society. All rights reserved.

We present results from near-infrared spectroscopy of 26 emission-line galaxies at z ∼ 2.2 and z ∼ 1.5 obtained with the Folded-port InfraRed Echellette (FIRE) spectrometer on the 6.5 m Magellan Baade telescope. The sample was selected from the WFC3 Infrared Spectroscopic Parallels survey, which uses the near-infrared grism of the Hubble Space Telescope Wide Field Camera 3 (WFC3) to detect emission-line galaxies over 0.3 ≲ z ≲ 2.3. Our FIRE follow-up spectroscopy (R ∼ 5000) over 1.0-2.5 μm permits detailed measurements of the physical properties of the z ∼ 2 emission-line galaxies. Dust-corrected star formation rates for the sample range from ∼5-100 MȮ yr-1 with a mean of 29 MȮ yr-1. We derive a median metallicity for the sample of 12 + log(O/H) = 8.34 or ∼0.45 ZȮ. The estimated stellar masses range from ∼108.5-109.5 MȮ, and a clear positive correlation between metallicity and stellar mass is observed. The average ionization parameter measured for the sample, log U ≈ -2.5, is significantly higher than what is found for most star-forming galaxies in the local universe, but similar to the values found for other star-forming galaxies at high redshift. We derive composite spectra from the FIRE sample, from which we measure typical nebular electron densities of ∼100-400 cm-3. Based on the location of the galaxies and composite spectra on diagnostic diagrams, we do not find evidence for significant active galactic nucleus activity in the sample. Most of the galaxies, as well as the composites, are offset diagram toward higher [O III]/Hβ at a given [N II]/Hα, in agreement with other observations of z ≳ 1 star-forming galaxies, but composite spectra derived from the sample do not show an appreciable offset from the local star-forming sequence on the [O III]/Hβ versus [S II]/Hα diagram. We infer a high nitrogen-to-oxygen abundance ratio from the composite spectrum, which may contribute to the offset of the high-redshift galaxies from the local star-forming sequence in the [O III]/Hβ versus [N II]/Hα diagram. We speculate that the elevated nitrogen abundance could result from substantial numbers of Wolf-Rayet stars in starbursting galaxies at z ∼ 2. © 2014. The American Astronomical Society. All rights reserved.

Near infrared slitless spectroscopy with the Wide Field Camera 3, on board the Hubble Space Telescope, offers a unique opportunity to study low-mass galaxy populations at high redshift (z ∼ 1-2). While most high-z surveys are biased toward massive galaxies, we are able to select sources via their emission lines that have very faint continua. We investigate the star formation rate (SFR)-stellar mass (M *) relation for about 1000 emission line galaxies identified over a wide redshift range of 0.3 ≲ z ≲ 2.3. We use the Hα emission as an accurate SFR indicator and correct the broadband photometry for the strong nebular contribution to derive accurate stellar masses down to M * ∼107 M ⊙. We focus here on a subsample of galaxies that show extremely strong emission lines (EELGs) with rest-frame equivalent widths ranging from 200 to 1500 Å. This population consists of outliers to the normal SFR-M * sequence with much higher specific SFRs (>10 Gyr-1). While on-sequence galaxies follow continuous star formation processes, EELGs are thought to be caught during an extreme burst of star formation that can double their stellar mass in a period of less than 100 Myr. The contribution of the starburst population to the total star formation density appears to be larger than what has been reported for more massive galaxies in previous studies. In the complete mass range 8.2 < log(M */M ⊙) <10 and a SFR lower completeness limit of about 2 M ⊙ yr-1 (10 M ⊙yr-1) at z ∼ 1 (z ∼ 2), we find that starbursts having EWrest(Hα) > 300, 200, and 100 Å contribute up to ∼13%, 18%, and 34%, respectively, to the total SFR of emission-line-selected sample at z ∼ 1-2. The comparison with samples of massive galaxies shows an increase in the contribution of starbursts toward lower masses. © 2014. The American Astronomical Society. All rights reserved.

We present the discovery and extensive early-time observations of the Type Ic supernova (SN) PTF12gzk. Our light curves show a rise of 0.8mag within 2.5hr. Power-law fits (f(t) (t - t 0)n) to these data constrain the explosion date to within one day. We cannot rule out a quadratic fireball model, but higher values of n are possible as well for larger areas in the fit parameter space. Our bolometric light curve and a dense spectral sequence are used to estimate the physical parameters of the exploding star and of the explosion. We show that the photometric evolution of PTF12gzk is slower than that of most SNe Ic. The high ejecta expansion velocities we measure (∼30, 000kms-1 derived from line minima fourdays after explosion) are similar to the observed velocities of broad-lined SNe Ic associated with gamma-ray bursts (GRBs) rather than to normal SN Ic velocities. Yet, this SN does not show the persistent broad lines that are typical of broad-lined SNe Ic. The host-galaxy characteristics are also consistent with GRB-SN hosts, and not with normal SN Ic hosts. By comparison with the spectroscopically similar SN 2004aw, we suggest that the observed properties of PTF12gzk indicate an initial progenitor mass of 25-35M ⊙ and a large ((5-10) × 10 51erg) kinetic energy, the later being close to the regime of GRB-SN properties. © 2012. The American Astronomical Society. All rights reserved.