Recent advances in radio astrometry with the VLBA have resulted in near micro-arcsecond accurate trigonometric parallax and proper motion measurements for masers in star forming regions. We are now poised to directly measure the full 3-dimensional locations and motions of every massive star forming region in the Milky Way and for the first time to map its spiral structure. Such measurements would also yield the full kinematics of the Milky Way and determine its fundamental parameters (Ro and To) with 1% accuracy. Coupled with other observations this would yield the distribution of mass among the various components (including dark matter) of the Milky Way.
The upcoming LISA mission is the only experiment that will allow us to study the Milky Way's structure using gravitational wave signals from Galactic double white dwarfs (DWDs). The total number of expected detections exceeds $10^5$. Furthermore, up to a hundred DWDs can be simultaneously detected in both gravitational and optical radiation (e.g. with Gaia and LSST as eclipsing), making DWDs ideal sources for performing a multi-messenger tomography of the Galaxy. We show that LISA will detect DWDs everywhere, mapping also the opposite side of the Galaxy. This complete coverage will: (1) provid…
As the remnants of stars with initial masses $\lesssim$ 8 M$_{\odot}$, white dwarfs contain valuable information on the formation histories of stellar populations. In this paper, we use deep, high-quality, u-band photometry from the Canada France Imaging Survey (CFIS), griz photometry from Pan-STARRS 1 (PS1), as well as proper motions from Gaia DR2, to select 25,156 white dwarf candidates over $\sim$4500 deg$^2$ using a reduced proper motion diagram. We develop a new white dwarf population synthesis code that returns mock observations of the Galactic field white dwarf population for a given st…
Aims: We study single and binary white dwarfs in the inner halo of the Milky Way in order to learn more about the conditions under which the population of halo stars was born, such as the initial mass function (IMF), the star formation history, or the binary fraction. Methods: We simulate the evolution of low-metallicity halo stars at distances up to ~ 3 kpc using the binary population synthesis code SeBa. We use two different white dwarf cooling models to predict the present-day luminosities of halo white dwarfs. We determine the white dwarf luminosity functions (WDLFs) for eight different ha…
The Milky Way galaxy is observed to have multiple components with distinct properties, such as the bulge, disk, and halo. Unraveling the assembly history of these populations provides a powerful test to the theory of galaxy formation and evolution, but is often restricted due to difficulties in measuring accurate stellar ages for low mass, hydrogen-burning stars. Unlike these progenitors, the "cinders" of stellar evolution, white dwarf stars, are remarkably simple objects and their fundamental properties can be measured with little ambiguity from spectroscopy. Here I report observations and an…
Spiral star-forming galaxies are complex astrophysical objects whose baryonic component is dominated by the disk, where most of the star formation resides. The metallicity in the disk is not uniform, and it usually decreases with the distance to the galaxy center, in the so-called radial metallicity gradient. Radial metallicity gradients have been successfully used to set important constraints on galaxy formation and their chemical evolution. This paper focuses on the implications of radial metallicity gradients measured with different probes for a variety of galaxies, and on the foreseen adva…
Chemodynamical models of our Galaxy that have analytic Extended Distribution Functions (EDFs) are likely to play a key role in extracting science from surveys in the era of Gaia.
We study a complete, colour-selected sample of double-degenerate binary systems containing extremely low mass (ELM) <0.25 Msol white dwarfs (WDs). We show, for the first time, that Milky Way disk ELM WDs have a merger rate of approximately 4 x 10^(-5)/yr due to gravitational wave radiation. The merger end-product depends on the mass ratio of the binary. The ELM WD systems that undergo stable mass transfer can account for >3% of AM CVn stars. More importantly, the ELM WD systems that may detonate merge at a rate comparable to the estimated rate of underluminous SNe, rare explosions estimated to…
Milky Way dwarf satellites are unique objects that encode the early structure formation and therefore represent a window into the high redshift Universe. So far, their study was conducted using electromagnetic waves only. The future Laser Interferometer Space Antenna (LISA) has the potential to reveal Milky Way satellites in gravitational waves emitted by double white dwarf (DWD) binaries. We investigate gravitational wave (GW) signals detectable by LISA as a possible tool for the identification and characterisation of the Milky Way satellites. We use the binary population synthesis technique …
We discuss the prospects for new deep, wide-angle surveys of the Galactic cool white dwarf populations using data from Pan-STARRS: the Panoramic Survey Telescope & Rapid Response System.
Whether supernovae are a significant source of dust has been a long-standing debate. The large quantities of dust observed in high-redshift galaxies raise a fundamental question as to the origin of dust in the Universe since stars cannot have evolved to the AGB dust-producing phase in high-redshift galaxies. In contrast, supernovae occur within several millions of years after the onset of star formation. This white paper focuses on dust formation in supernova ejecta with US-Extremely Large Telescope (ELT) perspective during the era of JWST and LSST.
The ionizing photons produced by massive stars are key actors in galaxy evolution. Ionizing photon production and escape is poorly understood. Improved space-based, spatially-resolved, multiplexed spectroscopic capabilities covering observed wavelengths of 1000 to 3000 Angstrom, in concert with spectroscopy from the ELTs and JWST, would lead to definitive answers as to how ionizing photons are produced and leaked, what populations of galaxies are responsible for ionizing photon leakage, what determines whether escape is possible, and how ionizing galaxy populations evolve over cosmic time.
Grand rotation curves (GRC) within ~400 kpc of M31 and the Milky Way were constructed by combining disk rotation velocities and radial velocities of satellite galaxies and globular clusters. The GRC for the Milky Way was revised using the most recent Solar rotation velocity. The derived GRCs were deconvolved into a de Vaucouleurs bulge, exponential disk, and a dark halo with the Navarro-Frenk-White (NFW) density profile by the least chi-squares fitting. Comparison of the best-fit parameters revealed similarity of the disks and bulges of the two galaxies, whereas the dark halo mass of M31 was f…
Hierarchical models of galaxy formation predict that galaxy mergers represent a significant transitional stage of rapid supermassive black hole (SMBH) growth. Yet, the connection between the merging process and enhanced active galactic nuclei (AGN) activity as well as the timescale of SMBH mergers remains highly uncertain. The breakthrough in reconciling the importance of galaxy mergers with black hole growth lies in a thoroughly-studied census of dual AGN across cosmic history, which will be enabled by next-generation observational capabilities, theoretical advances, and simulations. This whi…
High-redshift ($z$) proto-clusters will serve as testing grounds to probe the gas supply furnishing the emerging metals, stars, and large-scale structures we see at the current epoch. This work focuses on the major role large radio/millimeter (mm) single dish facilities will have in constraining the bulk, cold (T $= 10^{1-4}$K) molecular and atomic gas content. To highlight the need for large radio/mm single dishes, we calculate how the high-sensitivity of the Green Bank Telescope's (GBT) unblocked 100m aperture provides vital interferometric short-spacing coverage to support higher-resolution…
The study of the Milky Way structure is vital importance for a better understanding of the universe. This study digs deeper into the structure of Milky Way Galaxys with emphasis to its spiral arms. Multiple data sources were sought including the NASA websites. As found out, the Milky Way is a disk shaped galaxy composed of four spiral arms, two large and the rest are smaller. The spiral arms are regions of actively forming new stars dominated by young stars, dust and gas. Dust and gas are primary materials for the formation of new stars. This dust is also responsible for the reddish appearance…
Globular star clusters are among the first stellar populations to have formed in the Milky Way, and thus only a small sliver of their initial spectrum of stellar types are still burning hydrogen on the main-sequence today. Almost all of the stars born with more mass than 0.8 M_sun have evolved to form the white dwarf cooling sequence of these systems, and the distribution and properties of these remnants uniquely holds clues related to the nature of the now evolved progenitor stars. With ultra-deep HST imaging observations, rich white dwarf populations of four nearby Milky Way globular cluster…
We present orbits and their properties for 152 globular clusters of the Milky Way galaxy obtained using average Gaia DR2 proper motions and other astrometric data from the list of Vasiliev (2019). For orbit integrating we have used the axisymmetric model of the Galactic potential based on the Navarro-Frenk-White dark halo, and modified by Bajkova and Bobylev (2016) using circular velocities of Galactic objects in wide region of Galactocentric distances (up to 200 kpc) from Bhattacharjee et.al. (2014) catalog. Based on the analysis of the obtained orbits, we have modified the composition of the…
There is wide consensus that galaxy outflows are one of the most important processes determining the evolution of galaxies through cosmic time, for example playing a key role in shaping the galaxy mass function. Our understanding of outflows and their drivers, however, is in its infancy --- this is particularly true for the cold (neutral atomic and molecular) phases of outflows, which present observational and modeling challenges. Here we outline several key open questions, briefly discussing the requirements of the observations necessary to make progress, and the relevance of several existing…
Magnetism is one of the most important forces on the interstellar medium (ISM), anisotropically regulating the structure and star formation that drive galactic evolution. Recent high dynamic range observations of diffuse gas and molecular clouds have revealed new links between interstellar structures and the ambient magnetic field. ISM morphology encodes rich physical information, but deciphering it requires high-resolution measurements of the magnetic field: linear polarization of starlight and dust emission, and Zeeman splitting. These measure different components of the magnetic field, and …
This white paper highlights the crucial and urgent synergies required between WFIRST, Subaru Hyper Suprime-Cam or other >25m-class telescopes galaxy observations and SKA 21cm measurements to constrain the nature of reionization (ionization history and topology) and its sources.
We have compelling evidence for stellar-mass black holes (BHs) of ~5-80 M_sun that form through the death of massive stars. We also have compelling evidence for so-called supermassive BHs (10^5-10^10 M_sun) that are predominantly found in the centers of galaxies. We have very good reason to believe there must be BHs with masses in the gap between these ranges: the first ~10^9 M_sun BHs are observed only hundreds of millions of years after the Big Bang, and all theoretically viable paths to making supermassive BHs require a stage of "intermediate" mass. However, no BHs have yet been reliably de…
I present a brief review of some of the most recent and active topics of star formation process in the Milky Way using mid and far infrared observations, and motivated by the research being carried out by our science group using data gathered by the Spitzer and Herschel space telescopes. These topics include bringing together the scaling relationships found in extragalactic systems with that of the local nearby molecular clouds, the synthetic modeling of the Milky Way and estimates of its star formation rate.
White dwarf stars are a well-established tool for studying Galactic stellar populations. Two white dwarfs in a tight binary system offer us an additional messenger - gravitational waves - for exploring the Milky Way and its immediate surroundings. Gravitational waves produced by double white dwarf (DWD) binaries can be detected by the future Laser Interferometer Space Antenna (LISA). Numerous and widespread DWDs have the potential to probe shapes, masses and formation histories of the stellar populations in the Galactic neighbourhood. In this work we outline a method for estimating the total s…
Supermassive black holes are located at the center of most, if not all, massive galaxies. They follow close correlations with global properties of their host galaxies (scaling relations), and are thought to play a crucial role in galaxy evolution. Yet, we lack a complete understanding of fundamental aspects of their growth across cosmic time. In particular, we still do not understand: (1) whether black holes or their host galaxies grow faster and (2) what is the maximum mass that black holes can reach. The high angular resolution capability and sensitivity of 30-m class telescopes will revolut…
Future gravitational wave detectors, such as the Laser Interferometer Space Antenna (\textit{LISA}), will be able to resolve a significant number of the ultra compact stellar-mass binaries in our own Galaxy and its neighborhood. These will be mostly double white dwarf (DWD) binaries, and their underlying population characteristics can be directly correlated to the different properties of the Galaxy. In particular, with \textit{LISA} we will be able to resolve $\sim\mathcal{O}(10^4)$ binaries, while the rest will generate a confusion foreground signal. Analogously to how the total electromagnet…
The closest galaxy center, our own Central Molecular Zone (CMZ; the central 500 pc of the Milky Way), is a powerful laboratory for studying the secular processes that shape galaxies across cosmic time, from large-scale gas flows and star formation to stellar feedback and interaction with a central supermassive black hole. Research over the last decade has revealed that the process of converting gas into stars in galaxy centers differs from that in galaxy disks. The CMZ is the only galaxy center in which we can identify and weigh individual forming stars, so it is the key location to establish …
We present Brut, an algorithm to identify bubbles in infrared images of the Galactic midplane. Brut is based on the Random Forest algorithm, and uses bubbles identified by >35,000 citizen scientists from the Milky Way Project to discover the identifying characteristics of bubbles in images from the Spitzer Space Telescope. We demonstrate that Brut's ability to identify bubbles is comparable to expert astronomers. We use Brut to re-assess the bubbles in the Milky Way Project catalog, and find that 10-30% of the objects in this catalog are non-bubble interlopers. Relative to these interlopers, h…
A number of recent studies indicates a significant amount of ionized gas in a form of the hot gas halo around the Milky Way. The halo extends over the region of 100 kpc and may be acountable for the missing baryon mass. In this paper we calculate the contribution of the proposed halo to the dispersion measure (DM) of the pulsars. The Navarro, Frenk & White (NFW), Maller & Bullock (MB) and Feldmann, Hooper & Gnedin (FHG) density distibutions are considered for the gas halo. The data set includes pulsars with the distance known independently from the DM, e.g. pulsars in globular clusters, LMC, S…
We discuss the predicted performance of the HARMONI spectrograph and the ELT in the context of two specific science cases: resolved stellar populations of Local Volume galaxies and Galactic archaeology in dense environments. We have produced and analysed a set of simulated data-cubes using the HSIM software, mimicking observations across the giant elliptical galaxy Centaurus A and in the nuclear bulge of the Milky Way. We use our results to demonstrate the instruments capabilities to perform stellar absorption line spectroscopy in a large number of stars which will allow us to study the detail…
The transfer of circumstellar disk mass and momentum onto the protostar and out into the environment occurs via a variety of mechanisms including magnetospheric accretion, jets, outflows, and disk winds. The interplay of these processes determine both the conditions under which planet formation occurs and the lifetime of the disk. Metallic emission lines, along with the Balmer series of hydrogen, probe the kinematics of gas within the planet-forming and central regions of circumstellar disks. High-spectral resolution study of these emission lines provides critical information on mass and momen…
The inversion of the white dwarf luminosity function provides an independent way to prove the past star formation history of the Milky Way independent of any cosmological models. In Rowell & Hambly (2011), the effective volume method uses the average properties of all the objects in a given bin, so a significant amount of information is lost in the early stage of the analysis, in this work, I explore the possibility of assigning objects individually in a probabilistic way using the generalised Schmidt density estimator (1/Vmax).
High-accuracy absolute proper motions, radial velocities, and distances have now been measured for a number of dwarf-galaxy companions of the Milky Way, making it possible to study their 3D dynamics. Galactic orbits for 11 such galaxies (Fornax, Sagittarius, Ursa Minor, LMC, SMC, Sculptor, Sextans, Carina, Draco, Leo I, Leo II) have been derived using two previously refined models for the Galactic potential with the Navarro-Frenk-White and Allen-Santill'an expressions for the potential of the dark-matter halo, and two different masses for the Galaxy within 200 kpc - 0.75x10^12 Mo and 1.45x10^1…
We provide new values of the orbital parameters of 152 globular clusters, which are calculated using the new mean proper motions obtained from the Gaia EDR3 catalog data. The orbits were integrated 5 Gyr back in an axisymmetric three-component potential with a spherical bulge, disk component, and spherical dark halo in the Navarro-Frenk-White form, which we refined using the rotation curve of objects with large galactocentric distances up to 200 kpc. The obtained orbital parameters were compared with the orbital parameters of the same globular clusters calculated earlier in the same gravitatio…
We study the effect of different Type Ia SN nucleosynthesis prescriptions on the Milky Way chemical evolution. To this aim, we run detailed one-infall and two-infall chemical evolution models, adopting a large compilation of yield sets corresponding to different white dwarf progenitors (near-Chandrasekar and sub-Chandrasekar) taken from the literature. We adopt a fixed delay time distribution function for Type Ia SNe , in order to avoid degeneracies in the analysis of the different nucleosynthesis channels. We also combine yields for different Type Ia SN progenitors in order to test the contri…
The bandwith, sensitivity and sheer survey speed of the SKA offers unique potential for deep spectroscopic surveys of the Milky Way. Within the frequency bands available to the SKA lie many transitions that trace the ionised, radical and molecular components of the interstellar medium and which will revolutionise our understanding of many physical processes. In this chapter we describe the impact on our understanding of the Milky Way that can be achieved by spectroscopic SKA surveys, including "out of the box" early science with radio recombination lines, Phase 1 surveys of the molecular ISM u…
Diagnosing the physical and chemical conditions within star-forming galaxies (SFGs) is of paramount importance to understanding key components of galaxy formation and evolution: star-formation, gas enrichment, outflows, and accretion. Well established optical emission-line diagnostics used to discern such properties (i.e., metal content, density, strength/shape of ionizing radiation) will be observationally inaccessible for the earliest galaxies, emphasizing the need for robust, reliable interstellar medium (ISM) diagnostics at ultraviolet (UV) wavelengths. Calibrating these UV diagnostics req…
Crucial progress in our understanding of star formation and feedback will depend on the ability to obtain spatially resolved spectroscopic observations of \ion{H}{ii} regions, from which reliable instantaneous measurements of their physical conditions can be obtained. Acquiring these datasets across full galactic systems will prove crucial for obtaining population samples that enable us to understand the time evolution of similar regions, and the variability of conditions among coeval regions. Separating the spatial and temporal dependencies in such way for different physical processes involve…
Recent advances with the VLBA have resulted in ~10 micro-arcsec astrometry for compact sources in external galaxies, and measurement of the proper motion of Local Group galaxies has been demonstrated. With improved telescopes and equipment, we could greatly improve upon and expand these measurements, including a measurement of the proper motion of the Andromeda galaxy, which is key to understanding the history and fate of the Local Group. The combination of optical velocities and radio astrometric data would allow detailed modeling of the mass distributions of the disks, bulges, and dark matte…
The early phases of galaxy formation constitute one of the most exciting frontiers in astrophysics. It is during this era that the first luminous sources reionize the intergalactic medium - the moment when structure formation affects every baryon in the Universe. Here we argue that we will obtain a complete picture of this era by combining observations of galaxies with direct measurements of the reionization process: the former will provide a detailed understanding of bright sources, while the latter will constrain the (substantial) faint source population. We further describe how optimizing t…
Current X-ray observations and simulations show that gravitational lensing can be used to infer the structure near the event horizons of black holes, constrain the dynamics and evolution of black-hole accretion and outflows, test general relativity in the strong-gravity regime and place constraints on the evolution of dark matter in the lensing galaxies. These science goals currently cannot be achieved in a statistically large sample of z = 0.5 - 5 lensed quasars due to the limited capabilities of current X-ray telescopes and the relatively low number (~200) of known lensed quasars. The latter…
Since autumn 2008 an L-band 7-Feed-Array is operated for astronomical science at the 100-m radio telescope at Effelsberg. This receiver is used to perform an unbiased, fully sampled HI survey of the whole northern hemisphere observing both the galactic and extragalactic sky in parallel - the Effelsberg-Bonn HI survey (EBHIS). We present first results based on the Milky Way data. Up to now two larger coherent regions were mapped each covering about 2000 square degrees. One of these fields covers the northern part of the high-velocity cloud complex GCN. With the better angular resolution of the …
The outer regions of globular clusters can enable us to answer many fundamental questions concerning issues ranging from the formation and evolution of clusters and their multiple stellar populations to the study of stars near and beyond the hydrogen-burning limit and to the dynamics of the Milky Way. The outskirts of globular clusters are still uncharted territories observationally. A very efficient way to explore them is through high-precision proper motions of low-mass stars over a large field of view. The Wide Field InfraRed Survey Telescope (WFIRST) combines all these characteristics in a…
We present the Deep Synoptic Array (DSA-110) discovery and interferometric localization of the so far non-repeating FRB 20220319D. The FRB originates in a young, rapidly star-forming barred spiral galaxy, IRAS 02044$+$7048, at just 50 Mpc. Although the NE2001 and YMW16 models for the Galactic interstellar-medium (ISM) contribution to the DM of FRB 20220319D exceed its total observed DM, we show that uncertainties in these models accommodate an extragalactic origin for the burst. We derive a conservative upper limit on the DM contributed by the circumgalactic medium (CGM) of the Milky Way: the …
We determine the main properties of the Galactic binary black hole (BBH) population detectable by LISA and strategies to distinguish them from the much more numerous white dwarf binaries. We simulate BBH populations based on cosmological simulations of Milky Way-like galaxies and binary evolution models. We then determine their gravitational wave emission as observed by LISA and build mock catalogs. According to our model LISA will detect $\approx4(6)$ binary black holes assuming 4(10) years of operations. Those figures grow to $\approx6(9)$ when models are re-normalized to the inferred LIGO/V…
Nearby dwarf galaxies are local analogues of high-redshift and metal-poor stellar populations. Most of these systems ceased star formation long ago, but they retain signatures of their past that can be unraveled by detailed study of their resolved stars. Archaeological examination of dwarf galaxies with resolved stellar spectroscopy provides key insights into the first stars and galaxies, galaxy formation in the smallest dark matter halos, stellar populations in the metal-free and metal-poor universe, the nature of the first stellar explosions, and the origin of the elements. Extremely large t…
The wavelength range 912-2000A (hereafter far-UV) provides access to absorption lines of the interstellar medium (ISM), circumgalactic medium (CGM), and intergalactic medium (IGM) in phases spanning a wide range of ionization, density, temperature, and molecular gas fraction. Far-UV space telescopes have enabled detailed studies of the ISM in the Milky Way, paving the way to understand in particular depletion of elements by condensation onto dust grains, molecular gas formation pathways, ionization processes, and the dynamics of shocks. An interesting prospect is to transpose the same level of…
Galaxy evolution is driven by many complex interrelated processes as galaxies accrete gas, form new stars, grow their stellar masses and central black holes, and subsequently quench. The processes that drive these transformations is poorly understood, but it is clear that the local environment on multiple scales plays a significant role. Today's massive clusters are dominated by spheroidal galaxies with low levels of star formation while those in the field are mostly still actively forming their stars. In order to understand the physical processes that drive both the mass build up in galaxies …
We analyze the white dwarf population in miniJPAS, the first square degree observed with 56 medium-band, 145 A in width optical filters by the Javalambre Physics of the accelerating Universe Astrophysical Survey (J-PAS), to provide a data-based forecast for the white dwarf science with low-resolution (R ~ 50) photo-spectra. We define the sample of the bluest point-like sources in miniJPAS with r < 21.5 mag, point-like probability larger than 0.5, (u-r) < 0.80 mag, and (g-i) < 0.25 mag. This sample comprises 33 sources with spectroscopic information, 11 white dwarfs and 22 QSOs. We estimate the…
The X-ray regime is a largely underused resource for constraining interstellar dust grain models and improving our understanding of the physical processes that dictate how grains evolve over their lifetimes. This is mostly due to current detectors' relatively low sensitivity and high background, limiting the targets to the brightest sources. The improved sensitivity of the next generation of X-ray detectors will allow studies of much fainter sources, at much higher angular resolution, expanding our sampled sightlines in both quality and quantity.
Many recent observational and theoretical studies suggest that globular clusters (GCs) host compact object populations large enough to play dominant roles in their overall dynamical evolution. Yet direct detection, particularly of black holes and neutron stars, remains rare and limited to special cases, such as when these objects reside in close binaries with bright companions. Here we examine the potential of microlensing detections to further constrain these dark populations. Based on state-of-the-art GC models from the CMC Cluster Catalog, we estimate the microlensing event rates for black …
Over the past decade, research in resolved stellar populations has made great strides in exploring the nature of dark matter, in unraveling the star formation, chemical enrichment, and dynamical histories of the Milky Way and nearby galaxies, and in probing fundamental physics from general relativity to the structure of stars. Large surveys have been particularly important to the biggest of these discoveries. In the coming decade, current and planned surveys will push these research areas still further through a large variety of discovery spaces, giving us unprecedented views into the low surf…
Models of the chemical evolution of the interstellar medium, galaxies, and the Universe rely on our understanding of the amounts and chemical composition of the material returned by stars and supernovae. Stellar yields are obtained from stellar-evolution models, which currently lack predictive prescriptions of stellar mass loss, although it significantly affects stellar lifetimes, nucleosynthesis, and chemical ejecta. Galaxy properties are derived from observations of the integrated light of bright member stars. Stars in the late stages of their evolution are among the infrared-brightest objec…
We explore the formation of double-compact-object binaries in Milky Way (MW) globular clusters (GCs) that may be detectable by the Laser Interferometer Space Antenna (LISA). We use a set of 137 fully evolved GC models that, overall, effectively match the properties of the observed GCs in the MW. We estimate that, in total, the MW GCs contain $\sim21$ sources that will be detectable by LISA. These detectable sources contain all combinations of black hole (BH), neutron star, and white dwarf components. We predict $\sim7$ of these sources will be BH-BH binaries. Furthermore, we show that some of …
The Milky Way and all other galaxies are missing most of their baryons in that the ratio of the known baryonic mass to the gravitating mass (within the virial radius), is several times less than the cosmic ratio determined from WMAP. This implies that either the baryons never fell into galaxies or that powerful galactic winds removed most of the baryons. It is possible to discriminate between these two pathways if we can discover the missing baryons and measure its properties: spatial distribution; temperature; and metallicity. The missing baryons from galaxies are expected to have temperature…
