Search for H₃⁺ isotopologues toward CRL 2136 IRS 1

Context. Deuterated interstellar molecules frequently have abundances relative to their main isotopologues much higher than the overall elemental D-to-H ratio in the cold dense interstellar medium. H₃⁺ and its isotopologues play a key role in the deuterium fractionation; however, the abundances of these isotopologues have not been measured empirically with respect to H₃⁺ to date. Aims. Our aim was to constrain the relative abundances of H₂D⁺ and D₃⁺ in the cold outer envelope of the hot core CRL 2136 IRS 1. Methods. We carried out three observations targeting H₃⁺ and its isotopologues using the spectrographs CRIRES at the VLT, iSHELL at IRTF, and EXES on board SOFIA. In addition, the CO overtone band at 2.3 μm was observed by iSHELL to characterize the gas on the line of sight. Results. The H₃⁺ ion was detected toward CRL 2136 IRS 1 as in previous observations. Spectroscopy of lines of H₂D⁺ and D₃⁺ resulted in non-detections. The 3σ upper limits of N(H₂D⁺)/N(H₃⁺) and N(D₃⁺)/N(H₃⁺) are 0.24 and 0.13, respectively. The population diagram for CO is reproduced by two components of warm gas with the temperatures 58 and 530 K, assuming a local thermodynamic equilibrium (LTE) distribution of the rotational levels. Cold gas (<20 K) makes only a minor contribution to the CO molecular column toward CRL 2136 IRS 1. Conclusions. The critical conditions for deuterium fractionation in a dense cloud are low temperature and CO depletion. Given the revised cloud properties, it is no surprise that H₃⁺ isotopologues are not detected toward CRL 2136 IRS 1. The result is consistent with our current understanding of how deuterium fractionation proceeds

Search for H₃⁺ isotopologues toward CRL 2136 IRS 1

Context. Deuterated interstellar molecules frequently have abundances relative to their main isotopologues much higher than the overall elemental D-to-H ratio in the cold dense interstellar medium. H₃⁺ and its isotopologues play a key role in the deuterium fractionation; however, the abundances of these isotopologues have not been measured empirically with respect to H₃⁺ to date. Aims. Our aim was to constrain the relative abundances of H₂D⁺ and D₃⁺ in the cold outer envelope of the hot core CRL 2136 IRS 1. Methods. We carried out three observations targeting H₃⁺ and its isotopologues using the spectrographs CRIRES at the VLT, iSHELL at IRTF, and EXES on board SOFIA. In addition, the CO overtone band at 2.3 μm was observed by iSHELL to characterize the gas on the line of sight. Results. The H₃⁺ ion was detected toward CRL 2136 IRS 1 as in previous observations. Spectroscopy of lines of H₂D⁺ and D₃⁺ resulted in non-detections. The 3σ upper limits of N(H₂D⁺)/N(H₃⁺) and N(D₃⁺)/N(H₃⁺) are 0.24 and 0.13, respectively. The population diagram for CO is reproduced by two components of warm gas with the temperatures 58 and 530 K, assuming a local thermodynamic equilibrium (LTE) distribution of the rotational levels. Cold gas (<20 K) makes only a minor contribution to the CO molecular column toward CRL 2136 IRS 1. Conclusions. The critical conditions for deuterium fractionation in a dense cloud are low temperature and CO depletion. Given the revised cloud properties, it is no surprise that H₃⁺ isotopologues are not detected toward CRL 2136 IRS 1. The result is consistent with our current understanding of how deuterium fractionation proceeds

The Sword, April 2018

Contents Front Matter Letter From the Editor News Club Spotlight: 3D Printing Club How E-commerce Impacts Brick and Mortar Stores Omnibus Spending Plan Deadly Frat Pledge Vaping Epidemic in America\u27s Youth Miami Bridge Collapse Opinion Close-Minded Readers Won\u27t Believe This: A Liberal Solicites the Importance of Free Speech My Last Wish: Love and Unity Betsy DeVos Represents the Worst of American Politics Parkland, the NRA, and Preventative Measures: When Will it All End? What Defines Significance? Sports Female Athlete of the Month: Sheala Osborne Softball Looks to End Season Hot Minnesota Timberwolves Update Pitching Staff Leading the CSP in Conference Play Male Athlete of the Month: Josh Gaworski Lacrosse Team Showing they Belong in the GLIAC Golf Update Cold Air Don\u27t Care: Twins Open Up 2018 Season Swinging Amidst the Cold Weather Minnesota Wild Update Year in Review: 2017-2018 CSP Athletics Elite Curler, Madison Bear Set Eyes on the 2022 Olympics CSP Track and Field Sprints to Finish Line as Outdoor Championships Approach Arts and Variety Art and Design: Seniors Saying Goodbye to Concordia Food Review: Afro Deli Movie Review: The Dealth of Stalin Book Review: Ready Player One Writer Spotlight: Mia Morgan - Budding CSP Novelist Has a Bright Future Christus Chorus Spring Concert Recap Music Review: The Weeknd Reclaims His Roots with My Dear Melancholy Dance Spotlight: Ali Colburn Ceramics Biennial Recap Artist Spotlight: Danielle Odeen - Photographer, Graphic Designer, and Businesswoma

A reading workbook of stories and exercises with first grade vocabulary and fourth grade interests

Thesis (Ed.M.)--Boston Universit

How Do Galaxies Get Their Gas?

We examine the temperature history of gas accreted by forming galaxies in SPH simulations. About half the gas shock heats to roughly the virial temperature of the galaxy potential well before cooling, condensing, and forming stars, but the other half radiates its acquired gravitational energy at much lower temperatures, typically T<10^5 K, and the histogram of maximum gas temperatures is clearly bimodal. The "cold mode" of gas accretion dominates for low mass galaxies (M_baryon < 10^{10.3}Msun or M_halo < 10^{11.4}Msun), while the conventional "hot mode" dominates the growth of high mass systems. Cold accretion is often directed along filaments, allowing galaxies to efficiently draw gas from large distances, while hot accretion is quasi-spherical. The galaxy and halo mass dependence leads to redshift and environment dependence of cold and hot accretion rates, with cold mode dominating at high redshift and in low density regions today, and hot mode dominating in group and cluster environments at low redshift. Star formation rates closely track accretion rates, and we discuss the physics behind the observed environment and redshift dependence of galactic scale star formation. If we allowed hot accretion to be suppressed by conduction or AGN feedback, then the simulation predictions would change in interesting ways, perhaps resolving conflicts with the colors of ellipticals and the cutoff of the galaxy luminosity function. The transition between cold and hot accretion at M_h ~ 10^{11.4}Msun is similar to that found by Birnboim & Dekel (2003) using 1-d simulations and analytic arguments. The corresponding baryonic mass is tantalizingly close to the scale at which Kauffmann et al. (2003) find a marked shift in galaxy properties. We speculate on connections between these theoretical and observational transitions.Comment: 1 figure added, Appendix discussing SAMs added, some text changes. Matches the version accepted by MNRAS. 31 pages (MNRAS style), 21 figures,For high resolution version of the paper (highly recommended) follow http://www.astro.umass.edu/~keres/paper/ms2.ps.g

The self-regulated AGN feedback loop: the role of chaotic cold accretion

Supermassive black hole accretion and feedback play central role in the evolution of galaxies, groups, and clusters. I review how AGN feedback is tightly coupled with the formation of multiphase gas and the newly probed chaotic cold accretion (CCA). In a turbulent and heated atmosphere, cold clouds and kpc-scale filaments condense out of the plasma via thermal instability and rain toward the black hole. In the nucleus, the recurrent chaotic collisions between the cold clouds, filaments, and central torus promote angular momentum cancellation or mixing, boosting the accretion rate up to 100 times the Bondi rate. The rapid variability triggers powerful AGN outflows, which quench the cooling flow and star formation without destroying the cool core. The AGN heating stifles the formation of multiphase gas and accretion, the feedback subsides and the hot halo is allowed to cool again, restarting a new cycle. Ultimately, CCA creates a symbiotic link between the black hole and the whole host via a tight self-regulated feedback which preserves the gaseous halo in global thermal equilibrium throughout cosmic time.Comment: 4 pages, 1 figure; accepted for publication (IAUS 319

Adding Environmental Gas Physics to the Semi-Analytic Method for Galaxy Formation: Gravitational Heating

We present results of an attempt to include more detailed gas physics motivated from hydrodynamical simulations within semi-analytic models (SAM) of galaxy formation, focusing on the role that environmental effects play. The main difference to previous SAMs is that we include 'gravitational' heating of the intra-cluster medium (ICM) by the net surplus of gravitational potential energy released from gas that has been stripped from infalling satellites. Gravitational heating appears to be an efficient heating source able to prevent cooling in environments corresponding to dark matter halos more massive than $\sim 10^{13}$M$_{\odot}$. The energy release by gravitational heating can match that by AGN-feedback in massive galaxies and can exceed it in the most massive ones. However, there is a fundamental difference in the way the two processes operate. Gravitational heating becomes important at late times, when the peak activity of AGNs is already over, and it is very mass dependent. This mass dependency and time behaviour gives the right trend to recover down-sizing in the star-formation rate of massive galaxies. Abridged...Comment: replaced by accepted version to ApJ, some sections have been dropped and text has been added to others to include the referee's comments, several typos have been correcte