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Schematic structure of the starburst galaxies NGC 3310 (left) and NGC 3690 (right) as seen in the ultraviolet (2300Å2300Å) by the Faint Object Camera on HST (M95). The dots and crosses mark star clusters, with size indicating brightness. Isophotes show the distribution of diffuse light (after all clusters and their PSF halos are subtracted). The images have been rectified and oriented with north up, and east on the left. The distorted edges and occulting fingers of FOC are outlined. The two arcsec tick marks on the axis correspond to 175 pc and 430 pc for NGC 3310 and NGC 3690 respectively.
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The duration of starbursts is important for determining how they are regulated and the impact they have on their environment. Starbursts contain numerous prominent star clusters which typically comprise in total ~20% of the ultraviolet light, embedded in a diffuse glow of recently formed stars responsible for the dominant ~80%. Hubble Space Telesco...
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... (UV) images of starburst galax- ies with the Faint Object Camera imaging at λ ≈ 2300Å2300Å in order to examine the distribution of high mass stars which power starbursts. The results of our imaging study are given in Meurer et al. (1995;hereafter M95). The UV struc- ture of starbursts is well exemplified by NGC 3310 and NGC 3690 as shown in Fig. 1. Immediately striking are numerous prominent and compact star clusters. However, the total UV emission is dominated by a diffuse distribution of stars. Typically, this amounts to about 80% of the UV light within starbursts (M95). The nearest starbursts in our sample start to resolve into individual high mass stars which trace the ...
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Citations
... H I is usually the major phase observed in the outer regions of galaxy disks (Warren et al. 2004;Heald et al. 2011;Koribalski et al. 2018). H I emissions are also detected in filaments, plumes and/or bridges, tracing the gravitational interactions with neighboring galaxies (Koribalski et al. 2003;Meyer et al. 2004;Pearson et al. 2016). For many H I rich galaxies, the H I disks of spirals are usually much more extended than the stellar disks, which make them highly susceptible to external forces such as tidal interactions, gas accretion, and ram pressure stripping, while providing fuel for star formation (Meurer 1996;Serra et al. 2012;Bosma 2017;Koribalski et al. 2020). ...
... H I emissions are also detected in filaments, plumes and/or bridges, tracing the gravitational interactions with neighboring galaxies (Koribalski et al. 2003;Meyer et al. 2004;Pearson et al. 2016). For many H I rich galaxies, the H I disks of spirals are usually much more extended than the stellar disks, which make them highly susceptible to external forces such as tidal interactions, gas accretion, and ram pressure stripping, while providing fuel for star formation (Meurer 1996;Serra et al. 2012;Bosma 2017;Koribalski et al. 2020). Therefore, the amount and extent of H I in galaxies vary significantly with environment (Cortese & Hughes 2009;Lemonias et al. 2013;Dénes et al. 2014;Stevens & Brown 2017). ...
... Over the past decades, a number of H I surveys has been conducted to detect H I in the local universe (Koribalski et al. 2020), including the the H I Parkes All-Sky Survey (HIPASS; Staveley-Smith et al. 2000; Barnes et al. 2001;Meyer et al. 2004) in the southern hemisphere, the Northern HIPASS catalogue (NHICAT; Wong et al. 2006), and the Effelsberg Bonn H I Survey (EBHIS; Kerp et al. 2011) in northern hemisphere. The Arecibo Legacy Fast ALFA Survey (ALFALFA; Giovanelli et al. 2005a) provides improved spatial resolution and sensitivity over 7000 deg 2 . ...
We present the first data release of HI sources extracted from a pilot extra- galactic HI survey using the Five-hundred-meter Aperture Spherical radio Telescope (FAST). We extracted sources from three-dimensional(3D) spectral data cubes to perform interactive searching and computing, yielding global HI parameters for each source, extending redshift ranges of HI emission up to z = 0.04. A total of 544 ex- tragalactic HI sources have been detected by the pilot FAST HI drift scan survey covering part of the sky region in right ascension(R.A. or α) and declination(Dec or δ) range 00 h 47 m < R.A.(J2000) < 23 h 22 m and +24 ◦ < Dec.(J2000) < +43 ◦ . Of which, 528 sources are matched with optical counterparts via examination of digi- tal optical survey databases collected from NED ⋆ and Vizier ⋆⋆ data center, and 449 of them have optical velocities. Furthermore, We detect 36 galaxies with HI mass < 10 8 M ⊙ , which is significant for the study of low-mass systems in local universe. We present catalogs for all HI detections with signal to noise ratio(S/N) greater than 5.1. The data are classified into four categories based on their S/N and baseline qualities, which are flagged with code 1 to 4 :(1) 428 sources with signal of S/N > 6.5; (2) 54 sources with signal of 5.1 ≲ S/N ≲ 6.5; (3) 28 sources with relatively poor baselines; (4) 33 sources that are partly masked by strong RFIs. Besides, we find 16 HI sources that have not been matched with any counterparts in the existing galaxy catalogs. This data release can provide guidence for the future extragalactic HI survey with FAST.
... HI is usually the major phase observed in the outer regions of galaxy discs (Warren et al. 2004;Heald et al. 2011;Koribalski et al. 2018). HI emissions are also detected in filaments, plumes and/or bridges, tracing the gravitational interactions with neighbouring galaxies (Pearson et al. 2016;Koribalski et al. 2003;Meyer et al. 2004a). ...
... For many HI rich galaxies, the HI discs of spirals are usually much more extended than the stellar discs, which makes them highly susceptible to external forces such as tidal interactions, gas accretion, and ram pressure stripping, while providing fuel for star formation (Meurer 1996;Bosma 2017;Serra et al. 2012;Koribalski et al. 2020). Therefore, the amount and extent of HI in galaxies varies significantly with environment (Cortese & Hughes 2009;Lemonias et al. 2013;Dénes et al. 2014;Stevens & Brown 2017). ...
We present the first data release of HI sources extracted from a pilot extragalactic HI survey using the Five-hundred-meter Aperture Spherical radio Telescope (FAST). We extracted sources from three-dimensional(3D) spectral data cubes to perform interactive searching and computing, yielding global HI parameters for eachsource, extending redshift ranges of HI emission up to z = 0.04.A total of 544 extragalactic HI sources have been detected by the pilot FAST HI drift scan survey covering part of the sky region in right ascension(R.A. or $\alpha$) and declination(Dec or $\delta$) range $00^{\rm h} 47^{\rm m}< \rm R.A.(J2000)<23^{\rm h}22^{\rm m}$ and $+24^{\circ}<\rm Dec.(J2000)<+43^{\circ}$ . Of which, 528 sources are matched with optical counterparts via examination of digital optical survey databases collected from NED (http://ned.ipac.caltech.edu/Documents/Guides/Searches) and Vizier (https://vizier.u-strasbg.fr/viz-bin/VizieR-2) data center, and 449 of them have optical velocities. Furthermore, We detect 36 galaxies with HI mass $ < 10^8 M_{\odot}$, which is significant for the study of low-mass systems in local universe. We present catalogs for all HI detections with signal to noise ratio(S/N) greater than 5.1. The data are classified into four categories based on their S/N and baseline qualities, which are flagged with code 1 to 4 :(1) 422 sources with signal of S/N \textgreater 6.5; (2) 61 sources with signal of $\rm 5.1\lesssim S/N\lesssim 6.5$; (3) 28 sources with relatively poor baselines; (4) 33 sources that are partly masked by strong RFIs. Besides, we find 16 HI sources that have not been matched with any counterparts in the existing galaxy catalogs. This data release can provide guidence for the future extragalactic HI survey with FAST.
... The most commonly cited timescale for a starburst is 5 to 10 Myr, comparable to the lifetime of massive stars [341][342][343]. However, it has been suggested that the starburst phenomenon can be a longer and more global event than related by the lifetime of individual massive stars or pockets of intense star formation [344][345][346]. In this alternative viewpoint the short duration timescales are instead interpreted as a measure of the flickering created by currently active pockets of star formation that move around the galaxy. ...
In this report we review the important progress made in recent years towards understanding the experimental data on ultra-high-energy ($E \gtrsim 10^9$ GeV) cosmic rays. We begin with a general survey of the available data, including a description of the energy spectrum, the nuclear composition, and the distribution of arrival directions. At this point we also give a synopsis of experimental techniques. After that, we introduce the fundamentals of cosmic ray acceleration and energy loss during propagation, with a view of discussing the conjectured nearby sources. Next, we survey the state of the art regarding the high- and ultra-high-energy cosmic neutrinos which should be produced in association with the observed cosmic rays. These neutrinos can constitute key messengers identifying currently unknown cosmic accelerators, possibly in the distant universe, because their propagation is not influenced by background photon or magnetic fields. Subsequently, we summarize the phenomenology of cosmic ray air showers. We describe the hadronic interaction models used to extrapolate results from collider data to ultra-high energies and the main electromagnetic processes that govern the longitudinal shower evolution. Armed with these two principal shower ingredients and motivation from the underlying physics, we describe the different methods proposed to distinguish the primary particle species. In the end, we explore how ultra-high-energy cosmic rays can be used as probes of beyond standard model physics models.
In this report we review the important progress made in recent years towards understanding the experimental data on ultra-high-energy (E≳10⁹GeV) cosmic rays. We begin with a general survey of the available data, including a description of the energy spectrum, the nuclear composition, and the distribution of arrival directions. At this point we also give a synopsis of experimental techniques. After that, we introduce the fundamentals of cosmic ray acceleration and energy loss during propagation, with a view of discussing the conjectured nearby sources. Next, we survey the state of the art regarding the high- and ultra-high-energy cosmic neutrinos which may be produced in association with the observed cosmic rays. These neutrinos could constitute key messengers identifying currently unknown cosmic accelerators, possibly in the distant universe, because their propagation is not influenced by background photon or magnetic fields. Subsequently, we summarize the phenomenology of cosmic ray air showers. We describe the hadronic interaction models used to extrapolate results from collider data to ultra-high energies and the main electromagnetic processes that govern the longitudinal shower evolution. Armed with these two principal shower ingredients and motivation from the underlying physics, we describe the different methods proposed to distinguish the primary particle species. In the end, we explore how ultra-high-energy cosmic rays can be used as probes of beyond standard model physics models.
We map the spatial distribution of recent star formation over a few x 100 Myr
timescales in fifteen starburst dwarf galaxies using the location of young blue
helium burning stars identified from optically resolved stellar populations in
archival Hubble Space Telescope observations. By comparing the star formation
histories from both the high surface brightness central regions and the diffuse
outer regions, we measure the degree to which the star formation has been
centrally concentrated during the galaxies' starbursts, using three different
metrics for the spatial concentration. We find that the galaxies span a full
range in spatial concentration, from highly centralized to broadly distributed
star formation. Since most starbursts have historically been identified by
relatively short timescale star formation tracers (e.g., Halpha emission),
there could be a strong bias towards classifying only those galaxies with
recent, centralized star formation as starbursts, while missing starbursts that
are spatially distributed.
The starburst phenomenon can shape the evolution of the host galaxy and the surrounding intergalactic medium. The extent of the evolutionary impact is partly determined by the duration of the starburst, which has a direct correlation with both the amount of stellar feedback and the development of galactic winds, particularly for smaller mass dwarf systems. We measure the duration of starbursts in twenty nearby, ongoing, and "fossil" starbursts in dwarf galaxies based on the recent star formation histories derived from resolved stellar population data obtained with the Hubble Space Telescope. Contrary to the shorter times of 3-10 Myr often cited, the starburst durations we measure range from 450to650 Myr in fifteen of the dwarf galaxies and up to 1.3 Gyr in four galaxies; these longer durations are comparable to or longer than the dynamical timescales for each system. The same feedback from massive stars that may quench the flickering star formation does not disrupt the overall burst event in our sample of galaxies. While five galaxies present fossil bursts, fifteen galaxies show ongoing bursts and thus the final durations may be longer than we report here for these systems. One galaxy shows a burst that has been ongoing for only 20 Myr; we are likely seeing the beginning of a burst event in this system. Using the duration of the starbursts, we calculate that the bursts deposited 1053.9-1057.2 erg of energy into the interstellar medium through stellar winds and supernovae, and produced 3%–26% of the host galaxy's mass.
The duration of a starburst is a fundamental parameter affecting the evolution of galaxies yet, to date, observational constraints on the durations of starbursts are not well established. Here we study the recent star formation histories of three nearby dwarf galaxies to rigorously quantify the duration of their starburst events using a uniform and consistent approach. We find that the bursts range from ∼200 to ∼400 Myr in duration resolving the tension between the shorter timescales often derived observationally with the longer timescales derived from dynamical arguments. If these three starbursts are typical of starbursts in dwarf galaxies, then the short timescales (3–10 Myr) associated with starbursts in previous studies are best understood as "flickering" events which are simply small components of the larger starburst. In this sample of three nearby dwarfs, the bursts are not localized events. All three systems show bursting levels of star formation in regions of both high and low stellar density. The enhanced star formation moves around the galaxy during the bursts and covers a large fraction of the area of the galaxy. These massive, long-duration bursts can significantly affect the structure, dynamics, and chemical evolution of the host galaxy and can be the progenitors of "superwinds" that drive much of the recently chemically enriched material from the galaxy into the intergalactic medium.
Stable isotopes of precipitation, ground water and surface water measured on the windward side of East Maui from 0 to 3055 m altitude were used to determine recharge sources for stream flow and ground water. Correct interpretation of the hydrology using rainfall δ18O gradients with altitude required consideration of the influence of fog, as fog samples had isotopic signatures enriched by as much as 3‰ in δ18O and 21‰ in δD compared to volume-weighted average precipitation at the same altitude. The isotopic analyses suggested that fog drip was a major component of stream flow and shallow ground water at higher altitudes in the watershed. 18O/altitude gradients in rainfall were comparable for similar microclimates on Maui (this study) and Hawaii Island (1990–1995 study), however, East Maui δ18O values for rain in trade-wind and high-altitude microclimates were enriched compared to those from Hawaii Island. Isotopes were used to interpret regional hydrology in this volcanic island aquifer system. In part of the study area, stable isotopes indicate discharge of ground water recharged at least 1000 m above the sample site. This deep-flowpath ground water was found in springs from sea level up to 240 m altitude, indicating saturation to altitudes much higher than a typical freshwater lens. These findings help in predicting the effects of ground water development on stream flow in the area.
We use archival HST observations of resolved stellar populations to derive the star formation histories (SFHs) of 18 nearby starburst dwarf galaxies. In this first paper we present the observations, color-magnitude diagrams, and the SFHs of the 18 starburst galaxies, based on a homogeneous approach to the data reduction, differential extinction, and treatment of photometric completeness. We adopt a star formation rate (SFR) threshold normalized to the average SFR of the individual system as a metric for classifying starbursts in SFHs derived from resolved stellar populations. This choice facilitates finding not only currently bursting galaxies but also "fossil" bursts increasing the sample size of starburst galaxies in the nearby (D<8 Mpc) universe. Thirteen of the eighteen galaxies are experiencing ongoing bursts and five galaxies show fossil bursts. From our reconstructed SFHs, it is evident that the elevated SFRs of a burst are sustained for hundreds of Myr with variations on small timescales. A long >100 Myr temporal baseline is thus fundamental to any starburst definition or identification method. The longer lived bursts rule out rapid "self-quenching" of starbursts on global scales. The bursting galaxies' gas consumption timescales are shorter than the Hubble time for all but one galaxy confirming the short-lived nature of starbursts based on fuel limitations. Additionally, we find the strength of the H{\alpha} emission usually correlates with the CMD based SFR during the last 4-10 Myr. However, in four cases, the H{\alpha} emission is significantly less than what is expected for models of starbursts; the discrepancy is due to the SFR changing on timescales of a few Myr. The inherently short timescale of the H{\alpha} emission limits identifying galaxies as starbursts based on the current characteristics which may or may not be representative of the recent SFH of a galaxy. Comment: 53 pages, 11 figures
We present new K-band spectroscopy for a sample of 48 starburst galaxies, obtained using UKIRT in Hawaii. This constitutes a fair sample of the most common types of starburst galaxies found in the nearby Universe, containing galaxies with different morphologies, masses and metallicities, with far-infrared luminosity LIR<10¹⁰ L⊙. The variety of near-infrared spectral features shown by these galaxies implies different bursts characteristics, which suggests that we survey galaxies with different star formation histories or at different stages of their burst evolution.
Using synthetic starburst models, we conclude that the ensemble of parameters that best describes starburst galaxies in the nearby Universe is a constant rate of star formation, a Salpeter initial mass function (IMF) with an upper mass cut-off of Mup=30 M⊙ and bursts ages between 10 Myr and 1 Gyr. The model is fully consistent with the differences observed in the optical and far-infrared (FIR) between the different types of starbursts. It suggests that H ii galaxies have younger bursts and lower metallicities than starburst nucleus galaxies (SBNGs), while luminous infrared galaxies (LIRGs) have younger bursts but higher metallicities.
Although the above solution from the synthetic starburst model is fully consistent with our data, it may not constitute a strong constraint on the duration of the bursts and the IMF. A possible alternative may be a sequence of short bursts (which may follow an universal IMF) over a relatively long period of time. In favour of the multiple-burst hypothesis, we distinguish in our spectra some variations of near-infrared (NIR) features with the aperture that can be interpreted as evidence that the burst regions are not homogeneous in space and time. We also found that the burst stellar populations are dominated by early-type B stars, a characteristic which seems difficult to explain with only one evolved burst.
Our observations suggest that the starburst phenomenon must be a sustained or self-sustained phenomenon: either star formation is continuous in time, or multiple bursts happen in sequence over a relatively long period of time. The generality of our observations implies that this is a characteristic of starburst galaxies in the nearby Universe.
