Mid-J CO Emission From NGC 891: Microturbulent Molecular Shocks in Normal Star Forming Galaxies

We have detected the CO(6-5), CO(7-6), and [CI] 370 micron lines from the nuclear region of NGC 891 with our submillimeter grating spectrometer ZEUS on the CSO. These lines provide constraints on photodissociation region (PDR) and shock models that have been invoked to explain the H_2 S(0), S(1), and S(2) lines observed with Spitzer. We analyze our data together with the H_2 lines, CO(3-2), and IR continuum from the literature using a combined PDR/shock model. We find that the mid-J CO originates almost entirely from shock-excited warm molecular gas; contributions from PDRs are negligible. Also, almost all the H_2 S(2) and half of the S(1) line is predicted to emerge from shocks. Shocks with a pre-shock density of 2x10^4 cm^-3 and velocities of 10 km/s and 20 km/s for C-shocks and J-shocks, respectively, provide the best fit. In contrast, the [CI] line emission arises exclusively from the PDR component, which is best parameterized by a density of 3.2x10^3 cm^-3 and a FUV field of G_o = 100 for both PDR/shock-type combinations. Our mid-J CO observations show that turbulence is a very important heating source in molecular clouds, even in normal quiescent galaxies. The most likely energy sources for the shocks are supernovae or outflows from YSOs. The energetics of these shock sources favor C-shock excitation of the lines.Comment: 18 pages, 2 figures, 6 tables, accepted by Ap

First detections of the [NII] 122 {\mu}m line at high redshift: Demonstrating the utility of the line for studying galaxies in the early universe

We report the first detections of the [NII] 122 {\mu}m line from a high redshift galaxy. The line was strongly (> 6{\sigma}) detected from SMMJ02399-0136, and H1413+117 (the Cloverleaf QSO) using the Redshift(z) and Early Universe Spectrometer (ZEUS) on the CSO. The lines from both sources are quite bright with line-to-FIR continuum luminosity ratios that are ~7.0\times10^{-4} (Cloverleaf) and 2.1\times10^{-3} (SMMJ02399). With ratios 2-10 times larger than the average value for nearby galaxies, neither source exhibits the line-to-continuum deficits seen in nearby sources. The line strengths also indicate large ionized gas fractions, ~8 to 17% of the molecular gas mass. The [OIII]/[NII] line ratio is very sensitive to the effective temperature of ionizing stars and the ionization parameter for emission arising in the narrow-line region (NLR) of an AGN. Using our previous detection of the [OIII] 88 {\mu}m line, the [OIII]/[NII] line ratio for SMMJ02399-0136 indicates the dominant source of the line emission is either stellar HII regions ionized by O9.5 stars, or the NLR of the AGN with ionization parameter log(U) = -3.3 to -4.0. A composite system, where 30 to 50% of the FIR lines arise in the NLR also matches the data. The Cloverleaf is best modeled by a superposition of ~200 M82 like starbursts accounting for all of the FIR emission and 43% of the [NII] line. The remainder may come from the NLR. This work demonstrates the utility of the [NII] and [OIII] lines in constraining properties of the ionized medium.Comment: Accepted for publication in ApJ Letters; 16 pages, 2 tables, 3 figure

A quasioptical steering system for the CCAT/XSPEC submillimeter multi-object spectrometer

A two arm, opto-mechanical positioner mechanism is presented in this proceedings as a candidate steering system for the millimeter-wave XSPEC spectrograph. The design is well matched to the expected target density on the sky, and meeting all requirements of the Cerro Chajnantor Atacama Telescope (CCAT), site environmental conditions (e.g., operating temperature and power dissipation), and the positioning requirements themselves for acquiring and tracking astronomical objects whose light is fed into the XSPEC spectrograph units. The prototype design has been fabricated and tested for basic operations

Strong C+ emission in galaxies at z~1-2: Evidence for cold flow accretion powered star formation in the early Universe

We have recently detected the [CII] 157.7 micron line in eight star forming galaxies at redshifts 1 to 2 using the redshift(z) Early Universe Spectrometer (ZEUS). Our sample targets star formation dominant sources detected in PAH emission. This represents a significant addition to [CII] observations during the epoch of peak star formation. We have augmented this survey with observations of the [OI] 63 micron line and far infrared photometry from the PACS and SPIRE Herschel instruments as well as Spitzer IRS spectra from the literature showing PAH features. Our sources exhibit above average gas heating efficiency, many with both [OI]/FIR and [CII]/FIR ~1% or more. The relatively strong [CII] emission is consistent with our sources being dominated by star formation powered PDRs, extending to kpc scales. We suggest that the star formation mode in these systems follows a Schmidt-Kennicutt law similar to local systems, but at a much higher rate due to molecular gas surface densities 10 to 100 times that of local star forming systems. The source of the high molecular gas surface densities may be the infall of neutral gas from the cosmic web. In addition to the high [CII]/FIR values, we also find high [CII]/PAH ratios and, in at least one source, a cool dust temperature. This source, SWIRE 4-5, bears a resemblance in these diagnostics to shocked regions of Stephan's Quintet, suggesting that another mode of [CII] excitation in addition to normal photoelectric heating may be contributing to the observed [CII] line.Comment: Accepted for publication in Astrophysical Journal. To appear in December 20, 2014, V797 - 2 issu

Constraining the ISM Properties of the Cloverleaf Quasar Host Galaxy with Herschel Spectroscopy

We present Herschel observations of the far-infrared (FIR) fine-structure (FS) lines [C II]158 μm, [O I]63 μm, [O III]52 μm, and [Si II]35 μm in the z = 2.56 Cloverleaf quasar, and combine them with published data in an analysis of the dense interstellar medium (ISM) in this system. Observed [C II]158 μm, [O I]63 μm, and FIR continuum flux ratios are reproduced with photodissociation region (PDR) models characterized by moderate far-ultraviolet (FUV) radiation fields with G_0 = 0.3–1 × 10^3 and atomic gas densities n_H = 3–5 × 10^3 cm^(−3), depending on contributions to [C II]158 μm from ionized gas. We assess the contribution to the [C II]158 μm flux from an active galactic nucleus (AGN) narrow line region (NLR) using ground-based measurements of the [N II]122 μm transition, finding that the NLR can contribute at most 20%–30% of the observed [C II]158 μm flux. The PDR density and far-UV radiation fields inferred from the atomic lines are not consistent with the CO emission, indicating that the molecular gas excitation is not solely provided via UV heating from local star formation (SF), but requires an additional heating source. X-ray heating from the AGN is explored, and we find that X-ray-dominated region (XDR) models, in combination with PDR models, can match the CO cooling without overproducing the observed FS line emission. While this XDR/PDR solution is favored given the evidence for both X-rays and SF in the Cloverleaf, we also investigate alternatives for the warm molecular gas, finding that either mechanical heating via low-velocity shocks or an enhanced cosmic-ray ionization rate may also contribute. Finally, we include upper limits on two other measurements attempted in the Herschel program: [C II]158 μm in FSC 10214 and [O I]63 μm in APM 08279+5255

CO-Dark Star Formation and Black Hole Activity in 3C 368 at z = 1.131: Coeval Growth of Stellar and Supermassive Black Hole Masses

We present the detection of four far-infrared fine-structure oxygen lines, as well as strong upper limits for the CO(2-1) and [N II] 205 um lines, in 3C 368, a well-studied radio-loud galaxy at z = 1.131. These new oxygen lines, taken in conjunction with previously observed neon and carbon fine-structure lines, suggest a powerful active galactic nucleus (AGN), accompanied by vigorous and extended star formation. A starburst dominated by O8 stars, with an age of ~6.5 Myr, provides a good fit to the fine-structure line data. This estimated age of the starburst makes it nearly concurrent with the latest episode of AGN activity, suggesting a link between the growth of the supermassive black hole and stellar population in this source. We do not detect the CO(2-1) line, down to a level twelve times lower than the expected value for star forming galaxies. This lack of CO line emission is consistent with recent star formation activity if the star-forming molecular gas has low metallicity, is highly fractionated (such that CO is photodissociated through much of the clouds), or is chemically very young (such that CO has not yet had time to form). It is also possible, though we argue unlikely, that the ensemble of fine structure lines are emitted from the region heated by the AGN.Comment: 10 pages, 4 figures, 2 tables, accepted for publication in the Astrophysical Journa

Band-9 ALMA Observations of the [N II] 122 μm Line and FIR Continuum in Two High-z Galaxies

We present Atacama Large Millimeter Array (ALMA) observations of two high-redshift systems (SMMJ02399-0136 at z_1 ~ 2.8 and the Cloverleaf QSO at z_1 ~ 2.5) in their rest-frame 122 μm continuum (νsky ~ 650 GHz, λsky ~ 450 μm) and [N ii] 122 μm line emission. The continuum observations with a synthesized beam of ~0."25 resolve both sources and recover the expected flux. The Cloverleaf is resolved into a partial Einstein ring, while SMMJ02399-0136 is unambiguously separated into two components: a point source associated with an active galactic nucleus and an extended region at the location of a previously identified dusty starburst. We detect the [N ii] line in both systems, though significantly weaker than our previous detections made with the first generation z (Redshift) and Early Universe Spectrometer. We show that this discrepancy is mostly explained if the line flux is resolved out due to significantly more extended emission and longer ALMA baselines than expected. Based on the ALMA observations we determine that ≥75% of the total [N ii] line flux in each source is produced via star formation. We use the [N ii] line flux that is recovered by ALMA to constrain the N/H abundance, ionized gas mass, hydrogen- ionizing photon rate, and star formation rate. In SMMJ02399-0136 we discover it contains a significant amount (~1000 M_⊙ yr^(−1)) of unobscured star formation in addition to its dusty starburst and argue that SMMJ02399-0136 may be similar to the Antennae Galaxies (Arp 244) locally. In total these observations provide a new look at two well-studied systems while demonstrating the power and challenges of Band-9 ALMA observations of high-z systems