34 research outputs found
The prevalence and properties of cold gas inflows and outflows around galaxies in the local Universe
We perform a stacking analysis of the neutral
\nad\,5889,5895\,\AA\ ISM doublet using the SDSS DR7
spectroscopic data set to probe the prevalence and characteristics of cold
(T\,\,10\,K) galactic-scale gas flows in local (0.0250.1) inactive and AGN-host galaxies across the SFR-M plane. We
find low-velocity outflows to be prevalent in regions of high SFRs and stellar
masses (10 log M/M 11.5), however we do
not find any detections in the low mass (log M/M 10)
regime. We also find tentative detections of inflowing gas in high mass
galaxies across the star-forming population. We derive mass outflow rates in
the range of 0.14-1.74\,Myr and upper limits on inflow rates
<1\,Myr, allowing us to place constraints on the mass loading
factor (=/SFR) for use in simulations of the local
Universe. We discuss the fate of the outflows by comparing the force provided
by the starburst to the critical force needed to push the outflow outward, and
find the vast majority of the outflows unlikely to escape the host system.
Finally, as outflow detection rates and central velocities do not vary strongly
with the presence of a (weak) active supermassive black hole, we determine that
star formation appears to be the primary driver of outflows at 0.Comment: Accepted in MNRAS. 36 pages, 15 figure
A Spectroscopic Redshift Measurement for a Luminous Lyman Break Galaxy at z=7.730 using Keck/MOSFIRE
We present a spectroscopic redshift measurement of a very bright Lyman break
galaxy at z=7.7302+-0.0006 using Keck/MOSFIRE. The source was pre-selected
photometrically in the EGS field as a robust z~8 candidate with H=25.0 mag
based on optical non-detections and a very red Spitzer/IRAC [3.6]-[4.5]
broad-band color driven by high equivalent width [OIII]+Hbeta line emission.
The Lyalpha line is reliably detected at 6.1 sigma and shows an asymmetric
profile as expected for a galaxy embedded in a relatively neutral
inter-galactic medium near the Planck peak of cosmic reionization. The line has
a rest-frame equivalent width of EW0=21+-4 A and is extended with
V_FWHM=360+90-70 km/s. The source is perhaps the brightest and most massive z~8
Lyman break galaxy in the full CANDELS and BoRG/HIPPIES surveys, having
assembled already 10^(9.9+-0.2) M_sol of stars at only 650 Myr after the Big
Bang. The spectroscopic redshift measurement sets a new redshift record for
galaxies. This enables reliable constraints on the stellar mass, star-formation
rate, formation epoch, as well as combined [OIII]+Hbeta line equivalent widths.
The redshift confirms that the IRAC [4.5] photometry is very likely dominated
by line emission with EW0(OIII+Hbeta)= 720-150+180 A. This detection thus adds
to the evidence that extreme rest-frame optical emission lines are a ubiquitous
feature of early galaxies promising very efficient spectroscopic follow-up in
the future with infrared spectroscopy using JWST and, later, ELTs.Comment: 6 pages, 4 figures, small updates to match ApJL accepted versio
Closing in on the sources of cosmic reionization: first results from the GLASS-JWST program
The escape fraction of Lyman-continuum (LyC) photons () is a key
parameter for determining the sources of cosmic reionization at . At
these redshifts, owing to the opacity of the intergalactic medium, the LyC
emission cannot be measured directly. However, LyC leakers during the epoch of
reionization could be identified using indirect indicators that have been
extensively tested at low and intermediate redshifts. These include a high
[OIII]/[OII] flux ratio, high star-formation surface density, and compact
sizes. In this work, we present observations of 29
gravitationally lensed galaxies in the Abell 2744 cluster field. From a
combined analysis of JWST-NIRSpec and NIRCam data, we accurately derived their
physical and spectroscopic properties: our galaxies have low masses
, blue UV spectral slopes (), compact
sizes ( kpc), and high [OIII]/[OII] flux ratios. We confirm
that these properties are similar to those characterizing low-redshift LyC
leakers. Indirectly inferring the fraction of escaping ionizing photons, we
find that more than 80% of our galaxies have predicted values larger
than 0.05, indicating that they would be considered leakers. The average
predicted value of our sample is 0.12, suggesting that similar
galaxies at have provided a substantial contribution to cosmic
reionization.Comment: Accepted for publication in the 4. Extragalactic astronomy section of
A&A, 12 pages, 8 figure
Centrally concentrated molecular gas driving galactic-scale ionised gas outflows in star-forming galaxies
We perform a joint analysis of high spatial resolution molecular gas and star-formation rate (SFR) maps in main-sequence star-forming galaxies experiencing galactic-scale outflows of ionized gas. Our aim is to understand the mechanism that determines which galaxies are able to launch these intense winds. We observed CO(1â0) at 1-arcsec resolution with ALMA in 16 edge-on galaxies, which also have 2-arcsec spatial-resolution optical integral field observations from the SAMI Galaxy Survey. Half the galaxies in the sample were previously identified as harbouring intense and large-scale outflows of ionized gas (âoutflow typesâ) and the rest serve as control galaxies. The data set is complemented by integrated CO(1â0) observations from the IRAM 30-m telescope to probe the total molecular gas reservoirs. We find that the galaxies powering outflows do not possess significantly different global gas fractions or star-formation efficiencies when compared with a control sample. However, the ALMA maps reveal that the molecular gas in the outflow-type galaxies is distributed more centrally than in the control galaxies. For our outflow-type objects, molecular gas and star-formation are largely confined within their inner effective radius (reff), whereas in the control sample, the distribution is more diffuse, extending far beyond reff. We infer that outflows in normal star-forming galaxies may be caused by dynamical mechanisms that drive molecular gas into their central regions, which can result in locally enhanced gas surface density and star-formation
CANDELS multi-wavelength catalogs: source identification and photometry in the CANDELS COSMOS survey field
We present a multi-wavelength photometric catalog in the COSMOS field as part of the observations by the Cosmic Assembly Near-infrared Deep Extragalactic Legacy Survey. The catalog is based on Hubble Space Telescope Wide Field Camera 3 (HST/WFC3) and Advanced Camera for Surveys observations of the COSMOS field (centered at R.A.: 10h00m28s, Decl.:+02h12m21s). The final catalog has 38671 sources with photometric data in 42 bands from UV to the infrared (~0.3-8 ÎŒm). This includes broadband photometry from HST, CFHT, Subaru, the Visible and Infrared Survey Telescope for Astronomy, and Spitzer Space Telescope in the visible, near-infrared, and infrared bands along with intermediate- and narrowband photometry from Subaru and medium-band data from Mayall NEWFIRM. Source detection was conducted in the WFC3 F160W band (at 1.6 ÎŒm) and photometry is generated using the Template FITting algorithm. We further present a catalog of the physical properties of sources as identified in the HST F160W band and measured from the multi-band photometry by fitting the observed spectral energy distributions of sources against templates
Kraje ÄeskĂ© republiky - 2009
Obsahuje zĂĄkladnĂ ukazatele za ĂșroveĆ NUTS 2 a NUTS 3
Photometric and Spectroscopic analysis of lensed re-ionising sources at the frontier of the Universe
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