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We describe a Herschel Space Observatory 194-671 micron spectroscopic survey of a sample of 121 local luminous infrared galaxies and report the fluxes of the CO $J$ to $J$-1 rotational transitions for $4 \leqslant J \leqslant 13$, the [NII] 205 um line, the [CI] lines at 609 and 370 um, as well as additional and usually fainter lines. The CO spectral line energy distributions (SLEDs) presented here are consistent with our earlier work, which was based on a smaller sample, that calls for two distinct molecular gas components in general: (i) a cold component, which emits CO lines primarily at $J \lesssim 4$ and likely represents the same gas phase traced by CO (1-0), and (ii) a warm component, which dominates over the mid-$J$ regime ($4 < J < 10$) and is intimately related to current star formation. We present evidence that the CO line emission associated with an active galactic nucleus is significant only at $J > 10$. The flux ratios of the two [CI] lines imply modest excitation temperatures of 15 to 30 K; the [CI] 370 um line scales more linearly in flux with CO (4-3) than with CO (7-6). These findings suggest that the [CI] emission is predominately associated with the gas component defined in (i) above. Our analysis of the stacked spectra in different far-infrared (FIR) color bins reveals an evolution of the SLED of the rotational transitions of water vapor as a function of the FIR color in a direction consistent with infrared photon pumping., 244 pages, 23 figures, 7 tables, accepted for publication in the Astrophysical Journal Supplement Series

In this paper, we present the measurements of the [NII] 205micron line ([NII]205) for a flux-limited sample of 122 (ultra-)luminous infrared galaxies [(U)LIRGs] and 20 additional normal galaxies, obtained with the Herschel Space Observatory. We explore the far-infrared (FIR) color dependence of the [NII]205 (L[NII]205) to the total infrared (LIR) luminosity ratio, and find that L[NII]205/LIR only depends modestly on the 70-to-160 micron flux density ratio (f70/f160) when f70/f160 0.6. We also investigate the relation between L[NII]205 and star formation rate (SFR), and show that L[NII]205 has a nearly linear correlation with SFR, albeit the intercept of such relation varies somewhat with f60/f100, consistent with our previous conclusion that \NIIab\ emission can serve as a SFR indicator with an accuracy of ~0.4 dex, or ~0.2 dex if f60/f100 is known independently. Furthermore, together with the ISO measurements of [NII] 122 micron emission we use a total of ~200 galaxies to derive the local [NII]205 luminosity function (LF) by tying it to the known IR LF with a bivariate method. As a practical application, we also compute the local SFR volume density ($\dot{\rho}_{\rm SFR}$) using the newly derived SFR calibrator and LF. The resulting $\log\,\dot{\rho}_{\rm SFR} = -1.96\pm0.11$ $M_\odot$\,yr$^{-1}$\,Mpc$^{-3}$ agrees well with previous studies. Finally, we determine the electron densities ($n_e$) of the ionized medium for a subsample of 12 (U)LIRGs with both [NII]205 and [NII]122 data, and find that $n_e$ is in the range of ~1-100 cm$^{-3}$, with a median value of 22 cm$^{-3}$, Comment: Accepted for publication in ApJ

We present new IRAM 30m spectroscopic observations of the $\sim88$ GHz band, including emission from the CCH (n=1-0) multiplet, HCN (1-0), HCO+ (1-0), and HNC (1-0), for a sample of 58 local luminous and ultraluminous infrared galaxies from the Great Observatories All-sky LIRG Survey (GOALS). By combining our new IRAM data with literature data and Spitzer/IRS spectroscopy, we study the correspondence between these putative tracers of dense gas and the relative contribution of active galactic nuclei (AGN) and star formation to the mid-infrared luminosity of each system. We find the HCN (1-0) emission to be enhanced in AGN-dominated systems ($\langle$L'$_{HCN (1-0)}$/L'$_{HCO^+ (1-0)}\rangle=1.84$), compared to composite and starburst-dominated systems ($\langle$L'$_{HCN (1-0)}$/L'$_{HCO^+ (1-0)}\rangle=1.14$, and 0.88, respectively). However, some composite and starburst systems have L'$_{HCN (1-0)}$/L'$_{HCO^+ (1-0)}$ ratios comparable to those of AGN, indicating that enhanced HCN emission is not uniquely associated with energetically dominant AGN. After removing AGN-dominated systems from the sample, we find a linear relationship (within the uncertainties) between $\log_{10}$(L'$_{HCN (1-0)}$) and $\log_{10}$(L$_{IR}$), consistent with most previous findings. L'$_{HCN (1-0)}$/L$_{IR}$, typically interpreted as the dense gas depletion time, appears to have no systematic trend with L$_{IR}$ for our sample of luminous and ultraluminous infrared galaxies, and has significant scatter. The galaxy-integrated HCN (1-0) and HCO+ (1-0) emission do not appear to have a simple interpretation, in terms of the AGN dominance or the star formation rate, and are likely determined by multiple processes, including density and radiative effects., Comment: fix presentation of numerical value of y-intercept in eqs 1-3 to match forthcoming ApJ erratum. figure 6 and the conclusions are unaffected

To better characterize the global star formation (SF) activity in a galaxy, one needs to know not only the star formation rate (SFR) but also the rest-frame, far-infrared (FIR) color (e.g., the 60-to-100 $\mu$m color, $C(60/100)$] of the dust emission. The latter probes the average intensity of the dust heating radiation field and scales statistically with the effective SFR surface density in star-forming galaxies including (ultra-)luminous infrared galaxies [(U)LIRGs]. To this end, we exploit here a new spectroscopic approach involving only two emission lines: CO\,(7$-$6) at 372 $\mu$m and [NII] at 205 $\mu$m. For local (U)LIRGs, the ratios of the CO (7$-$6) luminosity ($L_{\rm CO\,(7-6)}$) to the total infrared luminosity ($L_{\rm IR}$; 8$-$1000 $\mu$m) are fairly tightly distributed (to within $\sim$0.12 dex) and show little dependence on $C(60/100)$. This makes $L_{\rm CO\,(7-6)}$ a good SFR tracer, which is less contaminated by active galactic nuclei (AGN) than $L_{\rm IR}$ and may also be much less sensitive to metallicity than $L_{\rm CO\,(1-0)}$. Furthermore, the logarithmic [NII] 205 $\mu$m to CO (7$-$6) luminosity ratio is fairly steeply (at a slope of $\sim$$-1.4$) correlated with $C(60/100)$, with a modest scatter ($\sim$0.23 dex). This makes it a useful estimator on $C(60/100)$ with an implied uncertainty of $\sim$0.15 [or $\lesssim$4 K in the dust temperature ($T_{\rm dust}$) in the case of a graybody emission with $T_{\rm dust} \gtrsim 30$ K and a dust emissivity index $\beta \ge 1$]. Our locally calibrated SFR and $C(60/100)$ estimators are shown to be consistent with the published data of (U)LIRGs of $z$ up to $\sim$6.5., Comment: 6 pages, 3 figures, 1 table; accepted for publication in the ApJ Letter

We present a comprehensive analysis of a broad band spectral line survey of the Orion Kleinmann-Low nebula (Orion KL), one of the most chemically rich regions in the Galaxy, using the HIFI instrument on board the Herschel Space Observatory. This survey spans a frequency range from 480 to 1907 GHz at a resolution of 1.1 MHz. These observations thus encompass the largest spectral coverage ever obtained toward this high-mass star-forming region in the sub-mm with high spectral resolution, and include frequencies $>$ 1 THz where the Earth's atmosphere prevents observations from the ground. In all, we detect emission from 39 molecules (79 isotopologues). Combining this dataset with ground based mm spectroscopy obtained with the IRAM 30 m telescope, we model the molecular emission from the mm to the far-IR using the XCLASS program which assumes local thermodynamic equilibrium (LTE). Several molecules are also modeled with the MADEX non-LTE code. Because of the wide frequency coverage, our models are constrained by transitions over an unprecedented range in excitation energy. A reduced $��^{2}$ analysis indicates that models for most species reproduce the observed emission well. In particular, most complex organics are well fit by LTE implying gas densities are high ($>$10$^6$ cm$^{-3}$) and excitation temperatures and column densities are well constrained. Molecular abundances are computed using H$_{2}$ column densities also derived from the HIFI survey. The distribution of rotation temperatures, $T_{\rm rot}$, for molecules detected toward the hot core is significantly wider than the compact ridge, plateau, and extended ridge $T_{\rm rot}$ distributions, indicating the hot core has the most complex thermal structure., Accepted to ApJ. 92 pages, 24 Figures, 9 Tables. Public data products may not be available yet

A sensitive broadband molecular line survey of the Sagittarius B2(N) star-forming region has been obtained with the HIFI instrument on the Herschel Space Observatory, offering the first high-spectral resolution look at this well-studied source in a wavelength region largely inaccessible from the ground (625-157 um). From the roughly 8,000 spectral features in the survey, a total of 72 isotopologues arising from 44 different molecules have been identified, ranging from light hydrides to complex organics, and arising from a variety of environments from cold and diffuse to hot and dense gas. We present an LTE model to the spectral signatures of each molecule, constraining the source sizes for hot core species with complementary SMA interferometric observations, and assuming that molecules with related functional group composition are cospatial. For each molecule, a single model is given to fit all of the emission and absorption features of that species across the entire 480-1910 GHz spectral range, accounting for multiple temperature and velocity components when needed to describe the spectrum. As with other HIFI surveys toward massive star forming regions, methanol is found to contribute more integrated line intensity to the spectrum than any other species. We discuss the molecular abundances derived for the hot core, where the local thermodynamic equilibrium approximation is generally found to describe the spectrum well, in comparison to abundances derived for the same molecules in the Orion KL region from a similar HIFI survey., Accepted to ApJ. 64 pages, 14 figures. Truncated abstract

This is the second paper studying the QSOs in the spitzer QUEST sample. Previously we presented new PAH measurements and argued that most of the observed far infrared (FIR) radiation is due to star-forming activity. Here we present spectral energy distributions (SEDs) by supplementing our data with optical, NIR and FIR observations. We define two sub-groups of ``weak FIR'' and ``strong FIR'' QSOs, and a third group of FIR non-detections. Assuming a starburst origin for the FIR, we obtain ``intrinsic'' AGN SEDs by subtracting a starburst template from the mean SEDs. The resulting SEDs are remarkably similar for all groups. They show three distinct peaks corresponding to two silicate emission features and a 3mic bump that we interpret as the signature of the hottest AGN dust. They also display drops beyond 20mic that we interpret as the signature of the minimum temperature (about 200K) dust. This component must be optically thin to explain the silicate emission and the slope of the long wavelength continuum. We discuss the merits of an alternative model where most of the FIR emission is due to AGN heating. Such models are unlikely to explain the properties of our QSOs but they cannot be ruled out for more luminous objects. We also find correlations between the luminosity at 5100A and two infrared starburst indicators: L(60mic) and L(PAH 7.7mic). The correlation of L(5100A) with L(60mic) can be used to measure the relative growth rates and lifetimes of the black hole and the new stars., Comment: 12 pages, 6 figures, accepted by ApJ