Download or read book Investigating the Star Formation Rates of Active Galactic Nucleus Hosts Relative to the Star Forming Main Sequence written by Nathan Cristello and published by . This book was released on 2024 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: A fundamental question in galaxy and black-hole evolution remains how galaxies and their supermassive black holes have evolved together over cosmic time. Specifically, it is still unclear how the position of X-ray active galactic nucleus (AGN) host galaxies with respect to the star-forming main sequence (MS) may change with the X-ray luminosity ($L_\mathrm{X}$) of the AGN or the stellar mass ($M_\star$) of the host galaxy. We use data from XMM-SERVS to probe this issue. XMM-SERVS is covered by the largest medium-depth X-ray survey (with superb supporting multiwavelength data) and thus contains the largest sample to date for study. To ensure consistency, we locally derive the MS from a large reference galaxy sample. In our analysis, we demonstrate that the turnover of the galaxy MS does not allow reliable conclusions to be drawn for high-mass AGNs, and we establish a robust safe regime where the results do not depend upon the choice of MS definition. Under this framework, our results indicate that less-massive AGN host-galaxies ($\log M_\star\sim9.5-10.5$ $M_\odot$) generally possess enhanced SFRs compared to their normal-galaxy counterparts while the more-massive AGN host galaxies \mbox{($\log M_\star\sim10.5-11.5$ $M_\odot$)} lie on or below the star-forming MS. Further, we propose an empirical model for how the placement of an AGN with respect to the MS (SFR$_{norm}$) evolves as a function of both $M_\star$ and $L_\mathrm{X}$.
Download or read book Exploring the Interplay Between Star Formation and Active Galactic Nuclei and the Role of Environment in Galaxy Evolution written by Jonathan Florez and published by . This book was released on 2021 with total page 432 pages. Available in PDF, EPUB and Kindle. Book excerpt: One of the central goals of extragalactic astronomy is to understand how galaxies grow their stellar mass and central black holes, the connection between star formation and active galactic nuclei (AGN), and the impact of environment on this growth. In this thesis, I utilize multiwavelength surveys that are both deep and wide, advanced computational codes that model the spectral energy distributions of galaxies with and without AGN, as well as state-of-the-art simulations of galaxy evolution in order to explore how galaxy properties are impacted by their surrounding environment and AGN activity. These studies explore galaxies over a redshift range of 0.015 z 0.023 (lookback time of ~ 0.2 to ~ 0.3 Gyr), and over a redshift range of 0.5 z 3.0 (lookback time of ~ 5 to ~ 12 Gyr). The large-area surveys used here provide some of the largest and most statistically robust samples to-date of rare massive galaxies (with stellar mass M [subscript *] 1011 M☉) and extremely luminous AGN (with X-ray luminosity L [subscript X] 1044 erg s−1) out to z ~ 3, thereby limiting the effects of cosmic variance and Poisson statistics. I analyze the observed stellar masses and star formation rates of galaxies as a function of environment and AGN activity, compare the empirical results to theoretical models of galaxy evolution, and discuss the implications of such comparisons. This work will provide significant guidance and constraints to the future development of theoretical models of galaxy growth. In Chapter 2 (Florez et al. 2021, ApJ, 906, 97) I measure the environmental dependence, where environment is defined by the distance to the third nearest neighbor, of multiple galaxy properties inside the Environmental COntext (ECO) catalog. I focus primarily on void galaxies at redshifts z = 0.015 - 0.023, which I define as the 10% of galaxies having the lowest local density. I compare the properties of void and non-void galaxies: baryonic mass, color, fractional stellar mass growth rate (FSMGR), morphology, and gas-to-stellar-mass ratio. The void galaxies typically have lower baryonic masses than galaxies in denser environments, and they display the properties expected of a lower mass population: they have more late-types, are bluer, have higher FSMGR, and are more gas rich. I also control for baryonic mass and investigate the extent to which void galaxies are different at fixed mass. I find that void galaxies are bluer, more gas-rich, and more star forming at fixed mass than non-void galaxies, which is a possible signature of galaxy assembly bias and other environmental processes. Furthermore, I show that these trends persist even at fixed mass and morphology, and I find that voids host a distinct population of early-types that are bluer and more star-forming than the typical red and quenched early-types. In addition to these empirical observational results, I also present theoretical results from mock catalogs with built-in galaxy assembly bias. I show that a simple matching of galaxy properties to (sub)halo properties, such as mass and age, can recover the observed environmental trends in the local galaxy population. In Chapter 3 (Florez et al. 2020, MNRAS, 497, 3273) I investigate the relation between AGN and star formation activity at 0.5 z 3 by analyzing 898 galaxies with high X-ray luminosity AGN (L [subscript X] 1044 erg s−1) and a large comparison sample of ~ 320,000 galaxies without such AGN. My samples are selected from a large (11.8 deg2) area in Stripe 82 that has multi-wavelength (X-ray to far-IR) data. The enormous comoving volume (~ 0.3 Gpc3) at 0.5
Download or read book Star Formation Across Galactic Environments written by Jason Young and published by . This book was released on 2012 with total page 98 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Principles of Star Formation written by Peter Bodenheimer and published by Springer Science & Business Media. This book was released on 2011-07-10 with total page 352 pages. Available in PDF, EPUB and Kindle. Book excerpt: Understanding star formation is one of the key fields in present-day astrophysics. This book treats a wide variety of the physical processes involved, as well as the main observational discoveries, with key points being discussed in detail. The current star formation in our galaxy is emphasized, because the most detailed observations are available for this case. The book presents a comparison of the various scenarios for star formation, discusses the basic physics underlying each one, and follows in detail the history of a star from its initial state in the interstellar gas to its becoming a condensed object in equilibrium. Both theoretical and observational evidence to support the validity of the general evolutionary path are presented, and methods for comparing the two are emphasized. The author is a recognized expert in calculations of the evolution of protostars, the structure and evolution of disks, and stellar evolution in general. This book will be of value to graduate students in astronomy and astrophysics as well as to active researchers in the field.
Download or read book A Detailed Study of Star Formation at Its Cosmic Peak written by Cody James Lamarche and published by . This book was released on 2019 with total page 157 pages. Available in PDF, EPUB and Kindle. Book excerpt: The star-formation-rate density of the universe has decreased by a factor of ~ 10 over the last 10 billion years, indicating a major change in either the efficiency with with galaxies form their stars or the availability of star-forming gas over the same time. In this thesis, we study the stellar populations within galaxies during the epoch of peak cosmic star-formation, ~ 10 billion years ago, using infrared observations of the ionized, neutral, and molecular phases of the interstellar medium (ISM) therein. In particular, we focus on two galaxies within this era, both of which have vigorous star-formation as well as active galactic nuclei (AGN), in an effort to learn more about the modes of star-formation at early times as well as the influence of AGN feedback on star-formation. As a first example, we examine the stellar population within 3C 368, a Fanaroff-Riley Class II (FR-II) galaxy at redshift 1.131. Our observations suggest a powerful AGN, accompanied by vigorous and extended star formation. We estimate the age of the starburst and find that it is nearly concurrent with the latest episode of AGN flaring, suggesting a link between the growth of the supermassive black hole and stellar population in this source. Our ionized-gas observations suggest a low gas-phase metallicity within this source, consistent with the weak molecular gas lines that we observe. We suggest that perhaps 3C 368 is accreting pristine molecular gas from an external source, thereby diluting its gas-phase metallicity. For our second example, we investigate the star-formation within SDP.11, a gravitationally-lensed galaxy at redshift 1.783. Our high-resolution gas and dust-continuum observations show intense star-formation in this source extended over several kiloparsecs. Gravitational-lens modeling further indicates that the star formation in this source is extended over a 3-5 kpc rotating disk, suggesting that the starburst present here may not be the result of a major merger, as is the case for local ultraluminous infrared galaxies (ULIRGs), but some other mechanism. The findings presented in this thesis support the idea of a different mode of star-formation being present in high-redshift galaxies. In contrast to local ULIRGs, which have intense star-formation confined to their centers, we find kiloparsec-scale star-forming disks present in galaxies during the epoch of peak cosmic star-formation. While local star-forming galaxies tend to be the product of major-mergers, high-redshift starburst galaxies may well be the product of another process, perhaps accretion of material from the cosmic web.
Download or read book Galaxies at High Redshift written by I. Pérez-Fournon and published by Cambridge University Press. This book was released on 2010-06-24 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book covers normal galaxies, distant galaxies, studies based on far-infrared diagnostics, quasar absorption lines, and the properties of nearby galaxies. The timely volume provides an essential reference for astronomers working in the field of high-redshift galaxies. It includes the lectures delivered at the XI Canary Islands Winter School of Astrophysics, and reviews scientific results as well as main questions in the field.
Download or read book Stellar Formation written by V C Reddish and published by Elsevier. This book was released on 2013-10-22 with total page 304 pages. Available in PDF, EPUB and Kindle. Book excerpt: Stellar Formation focuses on the properties, distributions, characteristics, and formation of stars and galaxies. The manuscript first offers information on locations of star formation, as well as the distribution of interstellar gas, clouds, and globules; spatial relationships between young stars and interstellar matter; and distribution of young stars. The book also tackles frequency distribution of stellar masses and aggregates of stars. The text ponders on the frequency distribution of cloud masses, rate and environment of star formation, and cloud structure in the interstellar gas. The publication also examines the fragmentation of clouds into protostars and the frequency distribution of protostar masses, rate of formation of stars, and evolution of galaxies. Discussions focus on random fragmentation, gravitational turbulence, and fragmentation induced by molecule formation. The manuscript is a vital reference for scientists and readers interested in stellar formation.
Download or read book Quenching Star Formation in Low mass Galaxies Hosting Active Galactic Nuclei written by Catherine Anne Witherspoon and published by . This book was released on 2023 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: This thesis aims to better understand the role active galactic nuclei (AGN) play in shutting down - quenching - star formation in low-mass galaxies. Using the Sloan Digital Sky Survey IV (SDSS-IV) Mapping Nearby Galaxies at Apache Point Observatory (MaNGA), we select a sample of low-mass galaxies with signatures of accretion onto a massive black hole. In order to disentangle the effects of environmental quenching mechanisms and AGN feedback, we investigate the group richness for active and inactive low-mass galaxies and their quiescent and star-forming sub-samples. We find that the quiescent low-mass galaxies hosting AGN prefer isolation or small groups suggesting that environmental process are not the primary quenching mechanisms. We also observed HI and CO gas in low-mass galaxies with AGN, and we find that the active galaxies are gas-depleted in both their atomic and molecular gas reservoirs, which indicates that these galaxies are in the process of quenching. Finally, we show that the mass-weighted stellar ages of low-mass galaxies hosting AGN have significantly younger stellar populations in their centers than their outskirts while the inactive galaxies have relatively flat radial stellar age gradients. These radial age gradients may be dependent on the strength of the AGN such that strong-AGN efficiently clear out the gas in the galaxy centers and prevent further star formation. Because weak-AGN cannot completely remove the centrally-located gas, the remaining gas in the galaxy is used for fueling the AGN and forming the last stars before the galaxy quenches. The combination of these works suggest that AGN could influence the star formation in low-mass galaxies and potentially be a dominant quenching mechanism.
Download or read book Understanding Star Formation and AGN Activity at Z 2 3 written by Kevin Nicholas Hainline and published by . This book was released on 2012 with total page 193 pages. Available in PDF, EPUB and Kindle. Book excerpt: There is compelling evidence that the growth of supermassive black holes and the stellar populations of their host galaxies are intricately linked. At the same time, the exact relationship between the buildup of stellar mass and the growth of supermassive black holes is still not well understood. At z ~ 2, both star-formation and Active Galactic Nuclei (AGN) activity in the universe were at peak levels, and this epoch is ideal for exploring the coevolution of stars and supermassive black holes. This dissertation examines high-redshift galaxies, looking at the particular properties of star-forming galaxies, the stellar populations of AGNs and the relationship between black hole and star-formation activity at z ~ 2 - 3. I have used the magnification afforded by gravitational lensing of z ~ 2 star-forming galaxies to measure important physical properties of the stars and gas in these galaxies. Using near-IR spectroscopy, I have calculated the metallicities, ionization parameters, star-formation rates, and dynamical masses for two galaxies which help to explain the differences between local- and high-redshift star-forming galaxies. The third and fourth chapters of this work cover the analysis of a sample of z ~ 2 - 3 AGNs drawn from the UV-selected Lyman Break Galaxy (LBG) survey. I present a rest-frame UV composite spectrum for this sample of AGNs. This spectrum shows many emission and absorption features, such as HI Lyman-alpha, NV1240, NIV]1483,1486, CIV1548,1550, HeII1640, and CIII]1907,1909. Redshifted SiIV1394 absorption provides evidence for outflowing high-ionization gas in these objects at speeds of 10^3 km/s. Finally, by using optical, near-IR, and mid-IR photometry, which covers the rest-frame UV to near-IR portions of the galaxies spectral energy distributions, I have modeled the SEDs of the AGNs that comprise this sample. I have developed a unique dual-component modeling approach that allows me to correct for the presence of an AGN. Based on these results, I have explored the relationship in the host galaxy between AGN activity, maturity of the stellar population, and regulation of star formation.
Download or read book The Physics and Evolution of Active Galactic Nuclei written by Hagai Netzer and published by Cambridge University Press. This book was released on 2013-09-16 with total page 369 pages. Available in PDF, EPUB and Kindle. Book excerpt: A comprehensive introduction to the theory underpinning our study of active galactic nuclei and the ways we observe them.
Download or read book Star Formation Rates of Galaxies written by Andreas Zezas and published by Cambridge University Press. This book was released on 2021-04-29 with total page 318 pages. Available in PDF, EPUB and Kindle. Book excerpt: Star-formation is one of the key processes that shape the current state and evolution of galaxies. This volume provides a comprehensive presentation of the different methods used to measure the intensity of recent or on-going star-forming activity in galaxies, discussing their advantages and complications in detail. It includes a thorough overview of the theoretical underpinnings of star-formation rate indicators, including topics such as stellar evolution and stellar spectra, the stellar initial mass function, and the physical conditions in the interstellar medium. The authors bring together in one place detailed and comparative discussions of traditional and new star-formation rate indicators, star-formation rate measurements in different spatial scales, and comparisons of star-formation rate indicators probing different stellar populations, along with the corresponding theoretical background. This is a useful reference for students and researchers working in the field of extragalactic astrophysics and studying star-formation in local and higher-redshift galaxies.
Download or read book Star Formation in Galaxies written by and published by . This book was released on 1987 with total page 810 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Exploring the Limits of Star Formation from the Extreme Environment of Galaxy Interactions to the Milky Way written by Amanda Lea Heiderman and published by . This book was released on 2012 with total page 584 pages. Available in PDF, EPUB and Kindle. Book excerpt: In this thesis, I explore the rate at which molecular gas is converted to stars through detailed studies of a sample of molecular clouds in the Milky Way, IFU spatially resolved observations of gas-rich nearby interacting galaxies, as well as the environmental dependence of star formation and galaxy morphology in a galaxy supercluster. This thesis is composed of three individual projects that investigate nearby star formation within the local 500 pc of our Sun, to neighboring extreme star forming environments of interacting starburst galaxies, and finally studying how star formation varies with galaxy morphology in a galaxy supercluster a z~0.165. I discuss the relation between the star formation rate (SFR) and molecular gas surface densities (e.g., Schmidt-Kennicutt relation) in Galactic star forming regions and find there is a discrepancy between my study and extragalactic relations. The discrepancy is attributed to extragalactic measurements that are averaged over large>kpc scales and include star forming molecular gas (above some threshold) and molecular gas the is not dense enough to form stars. I find a steep increase in the Galactic SFR-gas surface density relation indicative of a threshold for efficient star formation that is best fit to a broken power law with a linear slope above 129 Msun pc−2. I introduce the VIRUS-P Investigation of the eXtreme ENviroments of Starbursts (VIXENS) project which is a survey of interacting is a large integral field unit survey of nearby infrared bright (L_IR>3x1010 Lsun) interacting/starburst galaxies. The main goal of VIXENS is to investigate the relation between star formation and gas content on spatially resolved scales of ~0.1-1 kpc in the extreme star forming environments of interacting/starburst galaxies. The VIXENS sample is composed of systems in a range interaction stages with morphological signatures from early phase (close pairs) to late stage mergers (single system with multiple nuclei), SFRs, and gas surface densities. I highlight the first results from the VIXENS survey in the late interaction phase galaxy merger Arp 299. I find 1.3 kpc regions in Arp 299 to lie along the SFR-gas surface density relation found for mergers at high redshift, but this relation is highly dependent on the CO to molecular hydrogen (H2) conversion factor. I find evidence for a Galactic CO-to-H2 conversion factor using metallicity and dust temperature measurements, which would place 1.3 kpc regions in the Arp 299 merger in between the high redshift and Kennicutt-Schmidt relations. Comparing the SFR to dense gas surface densities as traced by HCN and HCO, I find an agreement between the spatially resolved measurements and that found on global scales in spirals and (ultra)luminous infrared galaxies. Finally, I present an investigation of the influence of environment on frequency, distribution, color, and star formation properties of galaxy mergers and non-interacting galaxies in the Abell 901/902 supercluster at z~0.165. I find galaxy mergers be preferentially blue in color and have an enhanced SFR by a factor of ~2 compared to non-interacting galaxies. This result may be due to a decrease in galaxy velocity dispersion in the cluster outskirt, favoring galaxy-galaxy interactions, or to interacting galaxies that are part of groups or field galaxies being accreted along cosmological filaments by the clusters. I compare to N-body simulations of groups and field galaxies accreting onto the clusters and find the fraction of mergers are similar to that predicated at group overdensities. I find the SFR of galaxies in the supercluster to be depressed compared to field galaxies in both the core and cluster outskirts, suggesting that an environmental process such as ram pressure stripping is effective throughout the cluster. The results of a modest SFR enhancement and a low merger fraction culminate in my finding that mergers contribute only a small fraction (between 10% and 15%) of the total SFR density of the Abell 901/902 clusters.
Download or read book Regulation of Star Formation Amidst Heating and Cooling in Galaxies and Galaxy Clusters written by Sravani Vaddi and published by . This book was released on 2016 with total page 342 pages. Available in PDF, EPUB and Kindle. Book excerpt: "Galaxy clusters are the largest gravitationally bound systems in the Universe and often host the largest galaxies (known as the brightest cluster galaxies (BCG)) at its centers. These BCG’s are embedded in hot 1-10 keV X-ray gas. A subset of galaxy clusters known as cool-core clusters show sharply peaked X-ray emission and high central densities, demonstrating cooling of the surrounding halo gas in timescales much shorter than a Hubble time. These observations led to the development of a simple cooling flow model. In the absence of an external heating process, a cooling flow model predicts that the hot intracluster medium gas in these dense cores would hydrostatically cool, generating cooling flows in the center of the cluster. This cooled gas will eventually collapse to form stars and contribute to the bulk of galaxy mass. The rates of star formation actually observed in the clusters however are far less than predicted by the cooling flow model, suggesting a non-gravitational heating source. Active galactic nuclei (AGN), galaxies hosting a supermassive black hole that ejects outflows via accretion, is currently the leading heating mechanism (referred to as AGN feedback) explaining the observed deficit in the star formation rates. AGN feedback also offers an elegant explanation to the observed black hole and galaxy co- evolution. Much of the evidence for AGN feedback has been obtained from studies focussed on galaxy clusters and luminous massive systems with little evidence that it occurs in more typical systems in the local universe. Our research investigates this less explored area to address the importance of AGN heating in the regulation of star formation in typical early type galaxies in the local universe. We selected a sample of 200+ early type, low redshift galaxies and carried out a multiple wavelength study using archival observed in the UV, IR and radio. Our results suggest that early type galaxies in the current epoch are rarely powerful AGN and AGN feedback is constrained to be low in our sample of low redshift, typical early type galaxies. Although heating from the AGN is powerful enough to suppress the cooling of the hot gas, it does not completely offset gas cooling at all times and substantial cooler gas exists in the cores of some galaxy clusters (cool-core clusters), the gas properties of which are not explained by AGN heating models alone. The second part of our research focuses on unravelling the mystery of the unknown heating source regulating star formation in galaxy clusters. We have obtained deep FUV spectroscopy using the HST cosmic origins spectrograph of two cool-core clusters A2597 and Zw3146. FUV spectral lines provide the much needed diagnostics capable of discriminating between various heating models, which was difficult with the standard optical line diagnostics. We investigate several heating/ionization mechanisms namely stellar photoionization, AGN photoionization, and shock heating. We use pre-run Mappings III photoionization code results to model the ionizing radiation field. In general, we notice that there is no one single model that provides a satisfactory explanation for the ionization state of gas. How- ever, we show that stellar and AGN photoionization alone are not enough to ionize the nebula in A2597 and speculate that, shock heating is the likely ionizing source."--Abstract.
Download or read book Scientific and Technical Aerospace Reports written by and published by . This book was released on 1991 with total page 486 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Investigating the Structure Star Formation and Stellar Mass of the Z written by Ashley Faloon and published by . This book was released on 2014 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The densest regions of the groups and isolated outskirt galaxies show hints of enhanced star formation activity. There is evidence of a bimodal distribution in the SFRs with stellar mass: the known main sequence of increasing SFR with increasing stellar mass, and a sub-main sequence population of partially quenched star forming galaxies. The sub-main sequence itself seems to be divided between environment-quenching and mass- quenching effects.We propose that the infalling groups in RCS 2319+00 are in varying stages of pre-processing, with their star formation activity level falling between that of the isolated supercluster galaxies and the less-active, more massive cluster cores. Overall, our results align with the theoretical models that predict galaxy pre-processing in group environments before final accretion onto cluster sized halos." --
Download or read book Advanced Lectures On The Starburst agn Connection written by Itziar Aretxaga and published by World Scientific. This book was released on 2001-04-24 with total page 387 pages. Available in PDF, EPUB and Kindle. Book excerpt: A group of leading experts in the field of starbursts and active galactic nuclei have joined hands to produce this review volume which covers the starburst-AGN connection, and the tests to be carried out with the upcoming new astronomical facilities to ascertain the relevance of both components to the formation and evolution of galaxies.The book is addressed to advanced graduate students and researchers in the fields of active galactic nuclei and young galaxies.
