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We follow up emission line galaxies identified through the near-infrared slitless HST /WFC3 WISP survey with VLT/FORS2 optical spectroscopy. Over 4 WISP fields, we targeted 85 of 138 line emission objects at |$0.4\lt z\lt 2$| identified in WFC3 spectroscopy. Half the galaxies are fainter than |$H_{AB}=24$|  mag, and would not have been included in many well-known surveys based on broad-band magnitude selection. We confirm 95 per cent of the initial WFC3 grism redshifts in the 38 cases where we detect lines in FORS2 spectroscopy. However, for targets which exhibited a single emission line in WFC3, up to 65 per cent at |$z\lt 1.28$| did not have expected emission lines detected in FORS2 and hence may be spurious (although this false-detection rate improves to 33 per cent using the latest public WISP emission line catalogue). From the Balmer decrement, the extinction of the WISP galaxies is consistent with |$A($| H  |$\alpha)=1$|  mag. From SED fits to multiband photometry including Spitzer |$3.6\, \mu$| m, we find a median stellar mass of |$\log _{10}(M_\star /{\rm M}_{\odot })=8.94$|⁠. Our emission-line-selected galaxies tend to lie above the star-forming main sequence (i.e. higher specific star formation rates). Using [O  iii ], [O  ii ], and H β lines to derive gas-phase metallicities, we find typically sub-solar metallicities, decreasing with redshift. Our WISP galaxies lie below the |$z=0$| mass–metallicity relation, and galaxies with higher star formation rates tend to have lower metallicity. Finally, we find a strong increase with redshift of the H α rest-frame equivalent width in this emission-line selected sample, with higher |$EW_0$| galaxies having larger [O  iii ]/H β and O32 ratios on average, suggesting lower metallicity or higher ionization parameter in these extreme emission line galaxies. [ABSTRACT FROM AUTHOR]

We present reduced images and catalogues of photometric and emission-line data (∼230 000 and ∼8000 sources, respectively) for the WFC3 (Wide Field Camera 3) Infrared Spectroscopic Parallel (WISP) survey. These data are made publicly available on the Mikulski Archive for Space Telescopes and include reduced images from various facilities: ground-based ugri, Hubble Space Telescope (HST) WFC3, and Spitzer IRAC (Infrared Array Camera). Coverage in at least one additional filter beyond the WFC3/IR data are available for roughly half of the fields (227 out of 483), with ∼20 per cent (86) having coverage in six or more filters from u band to IRAC 3.6  |$\mu$| m (0.35–3.6  |$\mu$| m). For the lower spatial resolution (and shallower) ground-based and IRAC data, we perform PSF (point spread function)-matched, prior-based, deconfusion photometry (i.e. forced-photometry) using the tphot software to optimally extract measurements or upper limits. We present the methodology and software used for the WISP emission-line detection and visual inspection. The former adopts a continuous wavelet transformation that significantly reduces the number of spurious sources as candidates before the visual inspection stage. We combine both WISP catalogues and perform spectral energy distribution fitting on galaxies with reliable spectroscopic redshifts and multiband photometry to measure their stellar masses. We stack WISP spectra as functions of stellar mass and redshift and measure average emission-line fluxes and ratios. We find that WISP emission-line sources are typically 'normal' star-forming galaxies based on the mass–excitation diagram ([O  iii ]/Hβ versus M ⋆; 0.74 < z grism < 2.31), the galaxy main sequence (SFR versus M ⋆; 0.30 < z grism < 1.45), S 32 ratio versus M ⋆ (0.30 < z grism < 0.73), and O 32 and R 23 ratios versus M ⋆ (1.27 < z grism < 1.45). [ABSTRACT FROM AUTHOR]

We present the first characterization of the average dust attenuation curve at z ∼ 1.3 by combining rest-frame ultraviolet through near-IR photometry with Balmer decrement (H α/H β) constraints for ∼900 galaxies with 8 ≲ log (M ⋆/M⊙) < 10.2 at 0.75 < z < 1.5 in the HST WFC3 IR Spectroscopic Parallel and 3D- HST grism surveys. Using galaxies in SDSS, we establish that the (H α + [N  ii ])/[O  iii ] line ratio and stellar mass are good proxies for the Balmer decrement in low-spectral resolution grism data when only upper limits on H β are available and/or H α is blended with [N  ii ]. The slope of the z ∼ 1.3 attenuation curve (⁠|$A(0.15\, \rm{\mu m})/A(V)=3.15$|⁠) and its normalization (RV  = 3.26) lie in-between the values found for z  = 0 and z ∼ 2 dust attenuation curves derived with similar methods. These provide supporting evidence that the average dust attenuation curve of star-forming galaxies evolves continuously with redshift. The z ∼ 1.3 curve has a mild 2175 Å feature (bump amplitude, Eb  = 0.83; ∼25 per cent that of the MW extinction curve), which is comparable to several other studies at 0 < z ≲ 3, and suggests that the average strength of this feature may not evolve significantly with redshift. The methods we develop to constrain dust attenuation from HST grism data can be applied to future grism surveys with JWST ,  Euclid , and RST. These new facilities will detect millions of emission line galaxies and offer the opportunity to significantly improve our understanding of how and why dust attenuation curves evolve. [ABSTRACT FROM AUTHOR]

We present Space Telescope Imaging Spectrograph emission-line spectra of the central regions of the spiral galaxies NGC 1300 and 2748. From the derived kinematics of the nuclear gas we have found evidence for central supermassive black holes in both galaxies. The estimated masses of the black holes in NGC 1300 and 2748 areand, respectively (both at the 95 per cent confidence level). These two black hole mass estimates contribute to the poorly sampled low-mass end of the nuclear black hole mass spectrum. [ABSTRACT FROM AUTHOR]