Physical Conditions in the ISM in Elliptical Galaxies
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Far-infrared Spectoscopy Elliptical Galaxies Norma↗
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A multiparametric analysis of the Einstein sample of early-type galaxies. 1: Luminosity and ISM parameters
We have conducted bivariate and multivariate statistical analysis of data measuring the luminosity and interstellar medium of the Einstein sample of early-type galaxies (presented by Fabbiano, Kim, & Trinchieri 1992). We find a strong nonlinear correlation between L(sub B) and L(sub X), with a power-law slope of 1.8 +/- 0.1, steepening to 2.0 +/- if we do not consider the Local Group dwarf galaxies M32 and NGC 205. Considering only galaxies with log L(sub X) less than or equal to 40.5, we instead find a slope of 1.0 +/- 0.2 (with or without the Local Group dwarfs). Although E and S0 galaxies have consistent slopes for their L(sub B)-L(sub X) relationships, the mean values of the distribution functions of both L(sub X) and L(sub X)/L(sub B) for the S0 galaxies are lower than those for the E galaxies at the 2.8 sigma and 3.5 sigma levels, respectively. We find clear evidence for a correlation between L(sub X) and the X-ray color C(sub 21), defined by Kim, Fabbiano, & Trinchieri (1992b), which indicates that X-ray luminosity is correlated with the spectral shape below 1 keV in the sense that low-L(sub X) systems have relatively large contributions from a soft component compared with high-L(sub X) systems. We find evidence from our analysis of the 12 micron IRAS data for our sample that our S0 sample has excess 12 micron emission compared with the E sample, scaled by their optical luminosities. This may be due to emission from dust heated in star-forming regions in S0 disks. This interpretation is reinforced by the existence of a strong L(sub 12)-L(sub 100) correlation for our S0 sample that is not found for the E galaxies, and by an analysis of optical-IR colors. We find steep slopes for power-law relationships between radio luminosity and optical, X-ray, and far-IR (FIR) properties. This last point argues that the presence of an FIR-emitting interstellar medium (ISM) in early-type galaxies is coupled to their ability to generate nonthermal radio continuum, as previously argued by, e.g., Walsh et al. (1989). We also find that, for a given L(sub 100), galaxies with larger L(sub X)/L(sub B) tend to be stronger nonthermal radio sources, as originally suggested by Kim & Fabbiano (1990). We note that, while L(sub B) is most strongly correlated with L(sub 6), the total radio luminosity, both L(sub X) and L(sub X)/L(sub B) are more strongly correlated with L(sub 6 CO), the core radio luminosity. These points support the argument (proposed by Fabbiano, Gioia, & Trinchieri 1989) that radio cores in early-type galaxies are fueled by the hot ISM.
Eskridge, Paul B.↗
ISM Parameters in the Normal Galaxy NGC 5713
We report ISO Long Wavelength Spectrometer (LWS) observations fo the Sbc(s) pec galaxy NGC 5713. We have obtained strong detections of the fine-structure forbidden transitions [C(sub ii)] 158(micro)m, [O(sub i)]63(micro)m, and [O(sub iii)] 88(micro)m, and significant upper limits for[N(sub ii)]122(micro)m, [O(sub iii)] 52(micro)m, and [N(sub iii)] 57(micro)m. We also detect the galaxy's dust continuum emission between 43 and 197 microns.
galaxies NGC5713 ISM infrared spectroscopy↗
Exploring Damped Ly Alpha System Host Galaxies Using Gamma-Ray Bursts
We present a sample of 45 Damped Ly-Alpha system [DLA; H I-N is greater than or equal to 2 x 10(exp. 20) cm(exp. -2)] counterparts (33 detections, 12 upper limits) which host gamma-ray bursts (GRB-DLAs) in order to investigate star formation and metallicity within galaxies hosting DLAs. Our sample spans z is approx. 2 - 6 and is nearly three times larger than any previously detected DLA counterparts survey based on quasar line-of-sight searches (QSO-DLAs). We report star formation rates (SFRs) from rest-frame UV photometry and spectral energy distribution modeling. We find that DLA counterpart SFRs are not correlated with either redshift or H I column density. Thanks to the combination of Hubble Space Telescope and ground-based observations, we also investigate DLA host star formation efficiency. Our GRB-DLA counterpart sample spans both higher efficiency and low efficiency star formation regions compared to the local Kennicutt-Schmidt relation, local star formation laws, and z is approximately 3 cosmological simulations. We also compare the depletion times of our DLA hosts sample to other objects in the local universe; our sample appears to deviate from the star formation efficiencies measured in local spiral and dwarf galaxies. Furthermore, we find similar efficiencies as local inner disks, SMC, and Lyman-break galaxy outskirts. Finally, our enrichment time measurements show a spread of systems with under- and over-abundance of metals, which may suggest that these systems had episodic star formation and a metal enrichment/depletion as a result of strong stellar feedback and/or metal inflow/outflow.
galaxies: high-redshift – galaxies: ISM – gala↗
ISM stripping from cluster galaxies and inhomogeneities in cooling flows
Analyses of the x ray surface brightness profiles of cluster cooling flows suggest that the mass flow rate decreases towards the center of the cluster. It is often suggested that this decrease results from thermal instabilities, in which denser blobs of gas cool rapidly and drop below x ray emitting temperatures. If the seeds for the thermal instabilities are entropy perturbations, these perturbations must enter the flow already in the nonlinear regime. Otherwise, the blobs would take too long to cool. Here, researchers suggest that such nonlinear perturbations might start as blobs of interstellar gas which are stripped out of cluster galaxies. Assuming that most of the gas produced by stellar mass loss in cluster galaxies is stripped from the galaxies, the total rate of such stripping is roughly M sub Interstellar Matter (ISM) approx. 100 solar mass yr(-1). It is interesting that the typical rates of cooling in cluster cooling flows are M sub cool approx. 100 solar mass yr(-1). Thus, it is possible that a substantial portion of the cooling gas originates as blobs of interstellar gas stripped from galaxies. The magnetic fields within and outside of the low entropy perturbations can help to maintain their identities, both by suppressing thermal conduction and through the dynamical effects of magnetic tension. One significant question concerning this scenario is: Why are cooling flows seen only in a fraction of clusters, although one would expect gas stripping to be very common. It may be that the density perturbations only survive and cool efficiently in clusters with a very high intracluster gas density and with the focusing effect of a central dominant galaxy. Inhomogeneities in the intracluster medium caused by the stripping of interstellar gas from galaxies can have a number of other effects on clusters. For example, these density fluctuations may disrupt the propagation of radio jets through the intracluster gas, and this may be one mechanism for producing Wide-Angle-Tail radio galaxies.
Soker, Noam↗
The life cycle of the Interstellar Medium in other galaxies
Gas in spiral galaxies cycles between the diffuse and dense phases as clouds collapse, form stars and are dispersed back into the ISM. Far infrared observations of continuum emission from interstellar dust and line emission from interstellar gas have revealed a wealth of information on the state of the ISM in galaxies of different morphological types. The analysis of these observations gives us information about the processes of star formation and about the evolution of the ISM. Star formation rates vary widely from galaxy to galaxy, with the rates in starburst galaxies being 10 - 100 times those in quiescent spiral galaxies. Far infrared spectroscopy of star-forming galaxies shows that the interstellar pressure increases with star formation rate. The structure of the interstellar medium in starburst galaxies is quite different from that of quiescent galaxies - much of the mass and volume are in HII regions and photodissociation regions. The size distribution of dust grains seems to depend on environment; small grains are abundant in the diffuse interstellar medium but not in dense molecular star forming regions. Quiescent spiral and elliptical galaxies contain a significant population of small grains, but starburst galaxies do not. Dwarf irregular galaxies also seem to contain few small grains; this may be the result of the higher UV flux in these galaxies. The star forming regions in dwarf irregulars also have a higher ratio of atomic to molecular gas than do those in the Galaxy. These results show that the ISM in galaxies of different morphological types reaches different equilibria, resulting in different modes of star formation and global galaxy evolution.
Knapp, G. R.↗
The interstellar medium in galaxies - An overview
Recent observational developments on the subject of the interstellar medium in galaxies are summarized, with emphasis placed on global properties. The properties and distribution of the ISM in the solar neighborhood and in the Galactic plane are examined and a number of results from the most important observational probes (HI, CO, and infrared) are described. A recent development is the observation of the ISM in galaxies of all morphological types, early to late. These developments are summarized and the properties of different types of galaxies are compared to one another. The origin of radio galaxies, the effect of environment, and the prospects for direct observations of ISM evolution in galaxies are discussed.
Knapp, G. R.↗
Evidence for a Multiphase ISM in Early Type Galaxies and Elliptical Galaxies with Strong Radio Continuum
We have observed NGC 1316 (Fornax A) with the ROSAT HRI. In this paper, we present the results of these observations and we complement them with the spectral analysis of the archival PSPC data. The spectral properties suggest the presence of a significant component of thermal X-ray emission (greater than 60%), amounting to approx. 10(exp 9) solar mass of hot ISM. Within 3 feet from the nucleus of NGC 1316, the HRI X-ray surface brightness falls as r(exp -2) following the stellar light. In the inner approx. 30 inch., however, the X-ray surface brightness is significantly elongated, contrary to the distribution of stellar light, which is significantly rounder within 10 inch. This again argues for a non-stellar origin of the X-ray emission. This flattened X-ray feature is suggestive of either the disk-like geometry of a rotating cooling flow and/or the presence of extended, elongated dark matter. By comparing the morphology of the X-ray emission with the distribution of optical dust patches, we find that the X-ray emission is significantly reduced at the locations where the dust patches are more pronounced, indicating that at least some of the X-ray photons are absorbed by the cold ISM. We also compare the distribution of the hot and cold ISM with that of the ionized gas, using recently obtained H(sub alpha) CCD data. We find that the ionized gas is distributed roughly along the dust patches and follows the large scale X-ray distribution at r greater than 1 foot from the nucleus. However, there is no one-to-one correspondence between ionized gas and hot gas. Both morphological relations and kinematics suggest different origins for hot and cold ISM. The radio jets in projection appear to pass perpendicularly through the central X-ray ellipsoid. Comparison of thermal and radio pressures suggests that the radio jets are confined by the surrounding hot gaseous medium.
Kim, Dong Woo↗
Soft X-ray Energy Spectra in the Wide-Field Galactic Disk Area Revealed with HaloSat
We analyzed data from HaloSat observations for five fields in the Galactic disk located far away from the Galactic center (135° < l < 254°) to understand the nature of soft X-ray energy emission in the Galactic disk. The fields have 14° diameter and were selected to contain no significant high-flux X-ray sources. All five HaloSat soft X-ray energy spectra (0.4–7 keV with energy resolution of < 100 eV below 1 keV) show a possibility of the presence of unresolved high-temperature plasma in the Galactic disk (UHTPGD) with a temperature of 0.8–1.0 keV and an emission measure of (8–11) × 10 −4 cm −6 pc in addition to the soft X-ray diffuse background components mainly studied at higher Galactic latitudes (solar wind charge exchange emission, Local Hot Bubble, Milky Way halo emission, and the cosmic X-ray background). This suggests that the UHTPGD is present across the whole Galactic disk. We also observed UHTPGD emission in a region with no bright sources in an XMM-Newton field contained within one of the HaloSat fields. The temperature and emission measure are consistent with those measured with HaloSat. Moreover, the stacked spectra of the X-ray pointlike sources and near-infrared-identified point sources such as stars in the XMM-Newton field also show a spectral feature similar to the UHTPGD emission. This suggests that the UHTPGD may partly originate from pointlike sources such as stars.
X-rays: diffuse background↗
Local interstellar medium and gamma-ray astronomy
The recent improvement of the calibration of the galaxy counts used as an interstellar absorption tracer modifies significantly the picture of the local interstellar medium (ISM). Consequently, previous analyses of the gamma ray emission from the local ISM involving galaxy counts have to be revised. The implications regarding the cosmic ray (CR) density in the local ISM are considered and in particular within Loop I, a nearby supernova remnant (SNR).
Lebrun, F.↗
C II 158 ??bservations of a Sample of Late-type Galaxies from the Virgo Cluster
We have observed 19 Virgo cluster spiral galaxies with the Long Wavelength Spectrometer (LWS) onboard ESAs Infrared Space Observatory (ISO) obtaining spectra around the [CII] 157.741 ??ine structure line.
Wavelength Spectrometer (LWS) Infrared Space Obser↗
The Most Distant H i Galaxies Discovered by the 500 m Dish FAST
Abstract Neutral hydrogen (Hi) is the primary component of the cool interstellar medium (ISM) and is the reservoir of fuel for star formation. Owing to the sensitivity of existing radio telescopes, our understanding of the evolution of the ISM in galaxies remains limited, as it is based on only a few hundred galaxies detected in Hibeyond the local Universe. With the high sensitivity of the Five-hundred-meter Aperture Spherical radio Telescope (FAST), we carried out a blind Hisearch, the FAST Ultra-Deep Survey, which extends to redshifts up to 0.42 and a sensitivity of 50μJy beam −1 . Here, we report the first discovery of six galaxies in Hi atz> 0.38. For these galaxies, the FAST angular resolution of ∼4′ corresponds to a mean linear size of ∼ 1.3 h 70 − 1 Mpc. These galaxies are among the most distant Hiemission detections known, with one having the most massive Hicontent ( 10 10.93 ± 0.04 h 70 − 2 M ⊙ ). Using recent data from the DESI survey and new observations with the Hale, Big Telescope Alt-azimuth, and Keck telescopes, optical counterparts are detected for all galaxies within the 3σpositional uncertainty ( 0.5 h 70 − 1 Mpc) and 200 km s −1 in recession velocity. Assuming that the dominant source of Hiis the identified optical counterpart, we find evidence of evolution in the Hicontent of galaxies over the last 4.2 Gyr. Our new high-redshift Higalaxy sample provides the opportunity to better investigate the evolution of cool gas in galaxies. A larger sample size in the future will allow us to refine our knowledge of the formation and evolution of galaxies.
Astronomy & Astrophysics↗
Tracing the Energetics of the Universe with Constellation-X: Example Scientific Investigations
Constellation-X will enable us to trace the energetics of a broad range of astrophysical phenomena owing to its capabilities for high spectral resolution X-ray spectroscopy. The dominant baryonic component of galaxy clusters and groups resides in the X-ray bandpass, and the hot phase of the ISM in galaxies harbors the heavy metal production from previous generation of stars. This talk will focus on a few example science questions that are expected to be important during the Constellation-X era. These include the nature of the missing baryons expected to reside in the hot portion of the Warm Hot Intergalactic Medium, which Constellation-X will address via absorption spectroscopy studies of background AGN. We will also discuss spatially resolved spectroscopy of metal enrichment and the effects of turbulence in clusters & groups and of starburst galaxy winds which deposit energy & metals into the Intergalactic Medium.
Hornschemeier, Ann↗
Star formation in active dwarf galaxies
Star formation and the ISM in active dwarf galaxies are studied based on data from the IRAS Point Source Catalog. The dwarf galaxies that show evidence of recent energetic star formation are generally also strong far-infrared emitters; thus, active current star formation is associated with a history of energetic star formation. A fraction of the galaxies considered here have a star formation rate that is significantly greater than the average rate in the recent past. Available gas is being consumed as efficiently in the presently active dwarfs as in the Milky Way. A primary difference between galaxies that are energetically forming stars and those that are not is the difference in gas mass, as well as the efficiency of star formation. The most important process may be the assembly of large amounts of gaseous material.
Thronson, Harley A., Jr.↗
A Comprehensive Characterization of Galaxy-cool CGM Connections at z < 0.4 with DESI Year 1 Data
We investigate the relationships between the cool circumgalactic medium (CGM), traced by Ca II absorption lines, and galaxy properties at z < 0.4 using ∼900,000 galaxy–quasar pairs within 200 kpc from the Year 1 data of the Dark Energy Spectroscopic Instrument (DESI). This large data set enables us to obtain composite spectra with sensitivity reaching to the mÅ level and to explore the Ca II absorption as a function of stellar mass, star formation rate (SFR), redshift, and galaxy types, including active galactic nuclei (AGNs). Our results show a positive correlation between the absorption strength and stellar mass of star-forming galaxies with $\langle$$W$$^{Ca II}_{0}$$\rangle$ α $M$$^{0.5}_{*}$ over 3 orders of magnitude in stellar mass from ∼10 8 to 10 11 M ⊙ , while such a mass dependence is weaker for quiescent galaxies. At a fixed mass, Ca II absorption is stronger around star-forming galaxies than quiescent ones especially within impact parameters <30 kpc. Among star-forming galaxies, the Ca II absorption further correlates with SFR, following ∝SFR 0.3 . However, in contrast to the results at higher redshifts, stronger absorption is not preferentially observed along the minor axis of star-forming galaxies, indicating a possible redshift evolution of CGM dynamics resulting from galactic feedback. Moreover, no significant difference between the properties of the cool gas around AGNs and galaxies is detected. Finally, we measure the absorption profiles with respect to the virial radius of dark matter halos and show that the total Ca II mass in the CGM is comparable to the Ca mass in the ISM of galaxies.
Circumgalactic medium↗
Gas metallicity distributions in SDSS-IV MaNGA galaxies: what drives gradients and local trends?
ABSTRACT The gas metallicity distributions across individual galaxies and across galaxy samples can teach us much about how galaxies evolve. Massive galaxies typically possess negative metallicity gradients, and mass and metallicity are tightly correlated on local scales over a wide range of galaxy masses; however, the precise origins of such trends remain elusive. Here, we employ data from SDSS-IV MaNGA to explore how gas metallicity depends on the local stellar mass density and on galactocentric radius within individual galaxies. We also consider how the strengths of these dependencies vary across the galaxy mass-size plane. We find that radius is more predictive of local metallicity than stellar mass density in extended lower-mass galaxies, while we find density and radius to be almost equally predictive in higher-mass and more compact galaxies. Consistent with previous work, we find a mild connection between metallicity gradients and large-scale environment; however, this is insufficient to explain variations in gas metallicity behaviour across the mass-size plane. We argue our results to be consistent with a scenario in which extended galaxies have experienced smooth gas accretion histories, producing negative metallicity gradients over time. We further argue that more compact and more massive systems have experienced increased merging activity that disrupts this process, leading to flatter metallicity gradients and more dominant density-metallicity correlations within individual galaxies.
79 ASTRONOMY AND ASTROPHYSICS↗
Conceptual Design of an Experiment to Study Dust Destruction by Astrophysical Shock Waves
A novel laboratory experimental design is described that will investigate the processing of dust grains in astrophysical shocks. Dust is a ubiquitous ingredient in the interstellar medium (ISM) of galaxies; however, its evolutionary cycle is still poorly understood. Especially shrouded in mystery is the efficiency of grain destruction by astrophysical shocks generated by expanding supernova remnants. While the evolution of these remnants is fairly well understood, the grain destruction efficiency in these shocks is largely unknown. The experiments described herein will fill this knowledge gap by studying the dust destruction efficiencies for shock velocities in the range of approximately 10-30 kilometers per second (microns per nanosecond), at which most of the grain destruction and processing in the ISM takes place. The experiments focus on the study of grain-grain collisions by accelerating small (1 millimeter) dust particles into a large (approximately 5-10 millimeter diameter) population; this simulates the astrophysical system well in that the more numerous, small grains impact and collide with the large population. Facilities that combine the versatility of high-power optical lasers with the diagnostic capabilities of X-ray free-electron lasers, e.g., the Matter in Extreme Conditions instrument at the SLAC (originally named Stanford Linear Accelerator Center) National Accelerator Laboratory, provide an ideal laboratory environment to create and diagnose dust destruction by astrophysically relevant shocks at the micron scale.
Manuel, M. J.-E.↗
The distribution of dust in edge-on galaxies: I. The global structure
ABSTRACT In this first paper in a series we present a study of the global dust emission distribution in nearby edge-on spiral galaxies. Our sample consists of 16 angularly large and 13 less spatially resolved galaxies selected from the DustPedia sample. To explore the dust emission distribution, we exploit the Herschel photometry in the range 100–500 $\mu $m. We employ Sérsic and 3D disc models to fit the observed 2D profiles of the galaxies. Both approaches give similar results. Our analysis unequivocally states the case for the presence of extraplanar dust in between 6 and 10 large galaxies. The results reveal that both the disc scale length and height increase as a function of wavelength between 100 and 500 $\mu $m. The dust disc scale height positively correlates with the dust disc scale length, similar to what is observed for the stellar discs. We also find correlations between the scale lengths and scale heights in the near- and far-infrared which suggest that the stellar discs and their dust counterparts are tightly connected. Furthermore, the intrinsic flattening of the dust disc is inversely proportional to the maximum rotation velocity and the dust mass of the galaxy: more massive spiral galaxies host, on average, relatively thinner dust discs. Also, there is a tendency for the dust-to-stellar scale height ratio to decrease with the dust mass and rotation velocity. We conclude that low-mass spiral galaxies host a diffuse, puffed-up dust disc with a thickness similar to that of the stellar disc.
79 ASTRONOMY AND ASTROPHYSICS↗