[en] We present the Team Keck Redshift Survey 2 (TKRS2), a near-infrared spectral observing program targeting selected galaxies within the CANDELS subsection of the GOODS-North Field. The TKRS2 program exploits the unique capabilities of the Multi-Object Spectrometer For Infra-Red Exploration (MOSFIRE), which entered service on the Keck I telescope in 2012 and contributes substantially to the study of galaxy spectral features at redshifts inaccessible to optical spectrographs. The TKRS2 project targets 97 galaxies drawn from samples that include z ≈ 2 emission-line galaxies with features observable in the JHK bands as well as lower-redshift targets with features in the Y band. We present a detailed measurement of MOSFIRE’s sensitivity as a function of wavelength, including the effects of telluric features across the YJHK filters. The largest utility of our survey is in providing rest-frame-optical emission lines for z > 1 galaxies, and we demonstrate that the ratios of strong, optical emission lines of z ≈ 2 galaxies suggest the presence of either higher N/O abundances than are found in z ≈ 0 galaxies or low-metallicity gas ionized by an active galactic nucleus. We have released all TKRS2 data products into the public domain to allow researchers access to representative raw and reduced MOSFIRE spectra

[en] We present high signal-to-noise, moderate resolution (R ≈ 2000) near-infrared spectra, as well as 10 μm imaging, for the brightest members of the central stellar cluster in the W40 H II region, obtained using the SpeX and MIRSI instruments at NASA's Infrared Telescope Facility. Using these observations combined with archival Spitzer Space Telescope data, we have determined the spectral classifications, extinction, distances, and spectral energy distributions (SEDs) for the brightest members of the cluster. Of the eight objects observed, we identify four main-sequence (MS) OB stars (one late-O, three early-B), two Herbig Ae/Be stars, and two low-mass young stellar objects (Class II). Strong He I absorption at 1.083 μm in the MS star spectra strongly suggests that at least some of these sources are in fact close binaries. Two out of the four MS stars also show significant infrared excesses typical of circumstellar disks. Extinctions and distances were determined for each MS star by fitting model stellar atmospheres to the SEDs. We estimate a distance to the cluster of between 455 and 535 pc, which agrees well with earlier (but far less precise) distance estimates. We conclude that the late-O star we identify is the dominant source of Lyman continuum luminosity needed to power the W40 H II region and is the likely source of the stellar wind that has blown a large (≈4 pc) pinched-waist bubble observed in wide-field mid-IR images. We also suggest that 3.6 cm radio emission observed from some of the sources in the cluster is likely not due to emission from ultracompact H II regions, as suggested in other work, due to size constraints based on our derived distance to the cluster. Finally, we also present a discussion of the curious source IRS 3A, which has a very strong mid-IR excess (despite its B3 MS classification) and appears to be embedded in a dusty envelope roughly 2700 AU in size.

[en] HST-10 is one of the largest proplyds in the Orion Nebula and is located approximately 1' SE of the Trapezium. Unlike other proplyds in Orion, however, the long-axis of HST-10 does not align with θ¹ C, but is instead aligned with the rotational axis of the HST-10 disk. This cannot be easily explained using current photoevaporation models. In this Letter, we present high spatial resolution near-infrared images of the Orion proplyd HST-10 using Keck/NIRC2 with the Laser Guide Star Adaptive Optics system, along with multi-epoch analysis of HH objects near HST-10 using Hubble Space Telescope (HST) WFPC2 and Advanced Camera for Surveys cameras. Our narrowband near-IR images resolve the proplyd ionization front (IF) and circumstellar disk down to 23 AU at the distance to Orion in Br γ, He I, H₂, and polycyclic aromatic hydrocarbon (PAH) emission. Br γ and He I emission primarily trace the IF (with the disk showing prominently in silhouette), while the H₂ and PAH emission trace the surface of the disk itself. PAH emission also traces small dust grains within the proplyd envelope which is asymmetric and does not coincide with the IF. The curious morphology of the PAH emission may be due to UV heating by both θ¹ COri and θ² AOri. Multi-epoch HST images of the HST-10 field show proper motion of three knots associated with HH 517, clearly indicating that HST-10 has a jet. We postulate that the orientation of HST-10 is determined by the combined ram pressure of this jet and the FUV-powered photo-ablation flow from the disk surface

[en] We present arcsecond resolution mid-infrared and millimeter observations of the center of the young stellar cluster AFGL961 in the Rosette molecular cloud. Within 0.2 pc of each other, we find an early B star embedded in a dense core, a neighboring star of similar luminosity with no millimeter counterpart, a protostar that has cleared out a cavity in the circumcluster envelope, and two massive, dense cores with no infrared counterparts. An outflow emanates from one of these cores, indicating a deeply embedded protostar, but the other is starless, bound, and appears to be collapsing. The diversity of states implies either that protostellar evolution is faster in clusters than in isolation or that clusters form via quasi-static rather than dynamic collapse. The existence of a pre-stellar core at the cluster center shows that some star formation continues after and in close proximity to massive, ionizing stars.

[en] We have observed a cluster forming clump (MM3) associated with the infrared dark cloud G34.43+00.24 in the 1.3 mm continuum and the CH₃OH, CS, ¹³CS, SiO, CH₃CH₂CN, and HCOOCH₃ lines with the Atacama Large Millimeter/submillimeter Array and in K-band with the Keck telescope. We have found a young outflow toward the center of this clump in the SiO, CS, and CH₃OH lines. This outflow is likely driven by a protostar embedded in a hot core, which is traced by the CH₃CH₂CN, HCOOCH₃, ¹³CS, and high excitation CH₃OH lines. The size of the hot core is about 800 × 300 AU in spite of its low mass (<1.1 M _☉), suggesting a high accretion rate or the presence of multiple star system harboring a few hot corinos. The outflow is highly collimated, and the dynamical timescale is estimated to be less than 740 yr. In addition, we have also detected extended emission of SiO, CS, and CH₃OH, which is not associated with the hot core and the outflow. This emission may be related to past star formation activity in the clump. Although G34.43+00.24 MM3 is surrounded by a dark feature in infrared, it has already experienced active formation of low-mass stars in an early stage of clump evolution

[en] We have used deep near-infrared observations with adaptive optics to discover a distributed population of low-mass protostars within the filamentary Infrared Dark Cloud G34.43+00.24. We use maps of dust emission at multiple wavelengths to determine the column density structure of the cloud. In combination with an empirically verified model of the magnitude distribution of background stars, this column density map allows us to reliably determine overdensities of red sources that are due to embedded protostars in the cloud. We also identify protostars through their extended emission in the K band, which comes from excited H₂ in protostellar outflows or reflection nebulosity. We find a population of distributed low-mass protostars, suggesting that low-mass protostars may form earlier than, or contemporaneously with, high-mass protostars in such a filament. The low-mass protostellar population may also produce the narrow line-width SiO emission observed in some clouds without high-mass protostars. Finally, we use a molecular line map of the cloud to determine the virial parameter per unit length along the filament and find that the highest mass protostars form in the most bound portion of the filament, as suggested by theoretical models.

[en] In this paper we present the MOSFIRE Deep Evolution Field (MOSDEF) survey. The MOSDEF survey aims to obtain moderate-resolution (R = 3000–3650) rest-frame optical spectra (∼3700–7000 Å) for ∼1500 galaxies at $1.37⩽<!--\; ???\; -->z⩽<!--\; ???\; -->3.80$ in three well-studied CANDELS fields: AEGIS, COSMOS, and GOODS-N. Targets are selected in three redshift intervals: $1.37⩽<!--\; ???\; -->z⩽<!--\; ???\; -->1.70$, $2.09⩽<!--\; ???\; -->z⩽<!--\; ???\; -->2.61$, and $2.95⩽<!--\; ???\; -->z⩽<!--\; ???\; -->3.80$, down to fixed $H_{\mathrm{A}\mathrm{B}}$ (F160W) magnitudes of 24.0, 24.5, and 25.0, respectively, using the photometric and spectroscopic catalogs from the 3D-HST survey. We target both strong nebular emission lines (e.g., [O ii] $\mathrm{\lambda <!--\; ??\; -->}\mathrm{\lambda <!--\; ??\; -->}3727,3730$, Hβ, [O iii] $\mathrm{\lambda <!--\; ??\; -->}\mathrm{\lambda <!--\; ??\; -->}4960,5008$, Hα, [N ii] $\mathrm{\lambda <!--\; ??\; -->}\mathrm{\lambda <!--\; ??\; -->}6550,6585$, and [S ii] $\mathrm{\lambda <!--\; ??\; -->}\mathrm{\lambda <!--\; ??\; -->}6718,6733$) and stellar continuum and absorption features (e.g., Balmer lines, Ca-ii H and K, Mgb, 4000 Å break). Here we present an overview of our survey, the observational strategy, the data reduction and analysis, and the sample characteristics based on spectra obtained during the first 24 nights. To date, we have completed 21 masks, obtaining spectra for 591 galaxies. For ∼80% of the targets we derive a robust redshift from either emission or absorption lines. In addition, we confirm 55 additional galaxies, which were serendipitously detected. The MOSDEF galaxy sample includes unobscured star-forming, dusty star-forming, and quiescent galaxies and spans a wide range in stellar mass ($\sim <!--\; ???\; -->{10}^9-<!--\; ???\; -->{10}^{11.5}{M}_{\odot <!--\; ???\; -->}$) and star formation rate ($\sim <!--\; ???\; -->{10}^0-<!--\; ???\; -->{10}^3{M}_{\odot <!--\; ???\; -->}{\mathrm{y}\mathrm{r}}^{-<!--\; ???\; -->1}$). The spectroscopically confirmed sample is roughly representative of an H-band limited galaxy sample at these redshifts. With its large sample size, broad diversity in galaxy properties, and wealth of available ancillary data, MOSDEF will transform our understanding of the stellar, gaseous, metal, dust, and black hole content of galaxies during the time when the universe was most active.

[en] We present Keck-I MOSFIRE near-infrared spectroscopy for a sample of 13 compact star-forming galaxies (SFGs) at redshift 2 ≤ z ≤ 2.5 with star formation rates of SFR ∼ 100 M _☉ yr^–1 and masses of log(M/M _☉) ∼10.8. Their high integrated gas velocity dispersions of σ_int =230₋₃₀⁺⁴⁰ km s^–1, as measured from emission lines of Hα and [O III], and the resultant M _*-σ_int relation and M _*-M _dyn all match well to those of compact quiescent galaxies at z ∼ 2, as measured from stellar absorption lines. Since log(M _*/M _dyn) =–0.06 ± 0.2 dex, these compact SFGs appear to be dynamically relaxed and evolved, i.e., depleted in gas and dark matter (<13₋₁₃⁺¹⁷%), and present larger σ_int than their non-compact SFG counterparts at the same epoch. Without infusion of external gas, depletion timescales are short, less than ∼300 Myr. This discovery adds another link to our new dynamical chain of evidence that compact SFGs at z ≳ 2 are already losing gas to become the immediate progenitors of compact quiescent galaxies by z ∼ 2.