Escape, Accretion or Star Formation? The Competing Depleters of Gas in the Quasar Markarian 231

We report on high resolution CO(1-0), CS(2-1) and 3mm continuum Combined Array for Research in Millimeter Astronomy (CARMA) observations of the molecular outflow host and nearest quasar Markarian 231. We use the CS(2-1) measurements to derive a dense gas mass within Mrk231 of $1.8\pm0.3\times10^{10}~M_\odot$, consistent with previous measurements. The CS(2-1) data also seem to indicate that the molecular disk of Mrk231 is forming stars at about normal efficiency. The high resolution CARMA observations were able to resolve the CO(1-0) outflow into two distinct lobes, allowing for a size estimate to be made and further constraining the molecular outflow dynamical time, further constraining the molecular gas escape rate. We find that 15% of the molecular gas within the Mrk231 outflow actually exceeds the escape velocity in the central kiloparsec. Assuming that molecular gas is not constantly being accelerated, we find the depletion timescale of molecular gas in Mrk231 to be 49Myr, rather than 32Myr, more consistent with the poststarburst stellar population observed in the system.Comment: 6 pages, 3 figures, 1 table, accepted by ApJ Letter

NGC 1266 as a Local Candidate for Rapid Cessation of Star Formation

We present new Spectrographic Areal Unit for Research on Optical Nebulae (SAURON) integral-field spectroscopy and Swift Ultraviolet Optical Telescope (UVOT) observations of molecular outflow host galaxy NGC 1266 that indicate NGC 1266 has experienced a rapid cessation of star formation. Both the SAURON maps of stellar population age and the Swift UVOT observations demonstrate the presence of young (<1 Gyr) stellar populations within the central 1 kpc, while existing Combined Array for Research in Millimeter-Wave Astronomy CO(1-0) maps indicate that the sites of current star formation are constrained to only the inner few hundred parsecs of the galaxy. The optical spectrum of NGC 1266 from Moustakas & Kennicutt reveal a characteristic poststarburst (K+A) stellar population, and Davis et al. confirm that ionized gas emission in the system originate from a shock. Galaxies with K+A spectra and shock-like ionized gas line ratios may comprise an important, overlooked segment of the poststarburst population, containing exactly those objects in which the active galactic nucleus (AGN) is actively expelling the star-forming material. While AGN activity is not the likely driver of the poststarburst event that occurred 500 Myr ago, the faint spiral structure seen in the Hubble Space Telescope Wide-field Camera 3 Y-, J- and H-band imaging seems to point to the possibility of gravitational torques being the culprit. If the molecular gas were driven into the center at the same time as the larger scale galaxy disk underwent quenching, the AGN might be able to sustain the presence of molecular gas for ≳ 1 Gyr by cyclically injecting turbulent energy into the dense molecular gas via a radio jet, inhibiting star formation

A Herschel and CARMA view of CO and [C II] in Hickson Compact groups

Understanding the evolution of galaxies from the starforming blue cloud to the quiescent red sequence has been revolutionized by observations taken with Herschel Space Observatory, and the onset of the era of sensitive millimeter interferometers, allowing astronomers to probe both cold dust as well as the cool interstellar medium in a large set of galaxies with unprecedented sensitivity. Recent Herschel observations of of H2-bright Hickson Compact Groups of galaxies (HCGs) has shown that [CII] may be boosted in diffuse shocked gas. CARMA CO(1-0) observations of these [CII]-bright HCGs has shown that these turbulent systems also can show suppression of SF. Here we present preliminary results from observations of HCGs with Herschel and CARMA, and their [CII] and CO(1-0) properties to discuss how shocks influence galaxy transitions and star formation.Comment: 4 pages, 3 figures, Proceedings for IAU Symposium 309, Galaxies in 3D across the Univers

The ATLAS^(3D) project – XXIX. The new look of early-type galaxies and surrounding fields disclosed by extremely deep optical images

Galactic archaeology based on star counts is instrumental to reconstruct the past mass assembly of Local Group galaxies. The development of new observing techniques and data reduction, coupled with the use of sensitive large field of view cameras, now allows us to pursue this technique in more distant galaxies exploiting their diffuse low surface brightness (LSB) light. As part of the ATLAS^(3D) project, we have obtained with the MegaCam camera at the Canada–France–Hawaii Telescope extremely deep, multiband images of nearby early-type galaxies (ETGs). We present here a catalogue of 92 galaxies from the ATLAS^(3D) sample, which are located in low- to medium-density environments. The observing strategy and data reduction pipeline, which achieve a gain of several magnitudes in the limiting surface brightness with respect to classical imaging surveys, are presented. The size and depth of the survey are compared to other recent deep imaging projects. The paper highlights the capability of LSB-optimized surveys at detecting new prominent structures that change the apparent morphology of galaxies. The intrinsic limitations of deep imaging observations are also discussed, among those, the contamination of the stellar haloes of galaxies by extended ghost reflections, and the cirrus emission from Galactic dust. The detection and systematic census of fine structures that trace the present and past mass assembly of ETGs are one of the prime goals of the project. We provide specific examples of each type of observed structures – tidal tails, stellar streams and shells – and explain how they were identified and classified. We give an overview of the initial results. The detailed statistical analysis will be presented in future papers

Observations of hydroxyl in early-type galaxies

We used Arecibo Observatory and the Green Bank Telescope to observe OH in twelve early type galaxies with known reservoirs of dense gas. We present three new detections of OH in absorption in the 1667 MHz line. One objective of our survey was to find evidence of molecular outflows, but our sensitivity, and the strength of the OH absorption, were insufficient to detect outflows. The detected sources have infrared luminosities and dust temperatures among the lowest of any galaxy detected in OH absorption. The ratio L_(HCN)=L_(CO), a measure of the dense gas fraction in galaxies, is a powerful selector of OH megamasers for galaxies with high infrared luminosity. In early-type galaxies, which have much lower infrared luminosities, L_(HCN)=L_(CO) is also a promising tool for discovering OH, but in absorption rather than in maser emission. In addition to dense molecular gas, a radio continuum source and a favorable line-of-sight to the observer are likely key factors in detecting OH absorbers

The ATLAS^(3D) project – XVIII. CARMA CO imaging survey of early-type galaxies

We present the Combined Array for Research in Millimeter Astronomy (CARMA) ATLAS^(3D) molecular gas imaging survey, a systematic study of the distribution and kinematics of molecular gas in CO-rich early-type galaxies. Our full sample of 40 galaxies (30 newly mapped and 10 taken from the literature) is complete to a ^(12)CO(1–0) integrated flux of 18.5 Jy km s^(−1),^1 and it represents the largest, best studied sample of its type to date. A comparison of the CO distribution of each galaxy to the g − r colour image (representing dust) shows that the molecular gas and dust distributions are in good agreement and trace the same underlying interstellar medium. The galaxies exhibit a variety of CO morphologies, including discs (50 per cent), rings (15 per cent), bars+rings (10 per cent), spiral arms (5 per cent) and mildly (12.5 per cent) and strongly (7.5 per cent) disrupted morphologies. There appear to be weak trends between galaxy mass and CO morphology, whereby the most massive galaxies in the sample tend to have molecular gas in a disc morphology. We derive a lower limit to the total accreted molecular gas mass across the sample of 2.48 × 10^(10) M_⊙, or approximately 8.3 × 10^8 M_⊙ per minor merger within the sample, consistent with minor merger stellar mass ratios

The ATLAS^(3D) Project – XXIII. Angular momentum and nuclear surface brightness profiles

We investigate nuclear light profiles in 135 ATLAS^(3D) galaxies for which the Hubble Space Telescope (HST) imaging is available and compare them to the large-scale kinematics obtained with the SAURON integral-field spectrograph. Specific angular momentum, λ_R, correlates with the shape of nuclear light profiles, where, as suggested by previous studies, cores are typically found in slow rotators and core-less galaxies are fast rotators. As also shown before, cores are found only in massive galaxies and only in systems with the stellar mass (measured via dynamical models) M ≳ 8 × 10^(10) M⊙. Based on our sample, we, however, see no evidence for a bimodal distribution of nuclear slopes. The best predictor for finding a core is based on the stellar velocity dispersion within an effective radius, σ_e, and specific angular momentum, where cores are found for λ_R ≲ 0.25 and σ_e ≳ 160 km s^(−1). We estimate that only about 10 per cent of nearby early-type galaxies contain cores. Furthermore, we show that there is a genuine population of fast rotators with cores. We also show that core fast rotators are morphologically, kinematically and dynamically different from core slow rotators. The cores of fast rotators, however, could harbour black holes of similar masses to those in core slow rotators, but typically more massive than those found in core-less fast rotators. Cores of both fast and slow rotators are made of old stars and found in galaxies typically lacking molecular or atomic gas (with a few exceptions). Core-less galaxies, and especially core-less fast rotators, are underluminous in the diffuse X-ray emission, but the presence of a core does not imply high X-ray luminosities. Additionally, we postulate (as many of these galaxies lack HST imaging) a possible population of core-less galaxies among slow rotators, which cannot be explained as face-on discs, but comprise a genuine sub-population of slow rotators. These galaxies are typically less massive and flatter than core slow rotators, and show evidence for dynamical cold structures and exponential photometric components. Based on our findings, major non-dissipative (gas-poor) mergers together with black hole binary evolution may not be the only path for formation of cores in early-type galaxies. We discuss possible processes for formation of cores and their subsequent preservation