1,721,687 research outputs found
A star-forming galaxy at z= 5.78 in the Chandra Deep Field South
Full text linkWe report the discovery of a luminous z = 5.78 star-forming galaxy in the Chandra Deep Field South. This galaxy was selected as an ‘i-drop’ from the GOODS public survey imaging with the Hubble Space Telescope/Advanced Camera for Surveys (object 3 in the work of Stanway, Bunker & McMahon 2003). The large colour of (i′−z′)AB = 1.6 indicated a spectral break consistent with the Lyman α forest absorption shortward of Lyman α at z≈ 6. The galaxy is very compact (marginally resolved with ACS with a half-light radius of 0.08 arcsec, so rhl 5. Our spectroscopic redshift for this object confirms the validity of the i′-drop technique of Stanway et al. to select star-forming galaxies atz≈ 6
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High-redshift AGN in the Chandra Deep Fields: the obscured fraction and space density of the sub-L∗ population
Full text linkThis article investigates the population of high-redshift (3≤z<6) active galactic nuclei (AGN) selected in the two deepest X-ray surveys, the 7 Ms Chandra Deep Field-South and 2 Ms Chandra Deep Field-North
Multiwavelength study of x-ray selected star-forming galaxies within the chandra deep field-south
Full text linkWe have combined multiwavelength observations of a selected sample of star-forming galaxies with galaxy evolution models in order to compare the results obtained for different star formation rate (SFR) tracers and to study the effect that the evolution of the star-forming regions has on them. We also aimed at obtaining a better understanding of the corrections due to extinction and nuclear activity on the derivation of the SFR. We selected the sample from Chandra data for the well studied region Chandra Deep Field-South (CDFS) and chose the objects that also have ultraviolet (UV) and infrared (IR) data from Galaxy Evolution Explorer (GALEX) and Great Observatories Origins Deep Survey (GOODS) Spitzer, respectively. Our main finding is that there is good agreement between the extinction corrected SFR(UV) and the SFR(X), and we confirm the use of X-ray luminosities as a trustful tracer of recent star formation activity. Nevertheless, at SFR(UV) larger than about 5Mꙩyr⁻¹ there are several galaxies with an excess of SFR(X) suggesting the presence of an obscured active galactic nucleus (AGN) not detected in the optical spectra.We conclude that the IR luminosity is driven by recent star formation even in those galaxies where the SFR(X) is an order of magnitude higher than the SFR(UV) and therefore may harbour an AGN. One object shows SFR(X) much lower than expected based on the SFR(UV); this SFR(X) ‘deficit’ may be due to an early transient phase before most of the massive X-ray binaries were formed. An X-ray deficit could be used to select extremely young bursts in an early phase just after the explosion of the first supernovae associated with massive stars and before the onset of massive X-ray binaries
The Chandra Deep Field-South Survey: 2 Ms Source Catalogs
No full textWe present point-source catalogs for the ~2 Ms exposure of the Chandra Deep Field-South (CDF-S) this is one of the two most sensitive X-ray surveys ever performed. The survey covers an area of ~436 arcmin2 and reaches on-axis sensitivity limits of ~1.9×1
Chandra Deep Field South : the optically faint population
No full textInternational audienceA not negligible fraction ( ~ 15\ detected in the 1 Msec observation of the Chandra Deep Field South (CDFS) are not detected down to R ∼= 27$, however they are registered in deep near-IR imaging. We use deep multicolor photometry from the VLT (FORS+ISAAC instruments), covering a broad wavelength range, to discuss the adequacy of such techniques for X-ray selected sources and to constrain the nature of this optically faint population
Chandra Deep Field South: the optically faint population
No full textA not negligible fraction (similar to 15%) of X-ray sources detected in the 1 Msec observation of the Chandra Deep Field South (CDFS) are not detected down to Rsimilar or equal to 27. however they are registered in deep near-IR imaging. We use deep multicolor photometry from the VLT (FORS+ISAAC instruments), covering a broad wavelength range, to discuss the adequacy of such techniques for X-ray selected sources and to constrain the nature of this optically faint population
The XMM deep survey in the Chandra Deep Field South
Full text linkThe Chandra Deep Field South (CDF-S) was observed by XMM-Newton for a total
of about 3 Ms in many periods over the past decade (2001-2002 and 2008-2009).
The main goal of the survey was to obtain good quality X-ray spectroscopy of
the AGN responsible for the bulk of the X-ray background. We will present the
scientific highlights of the XMM-Newton survey and briefly discuss the
perspectives of future observations to pursue XMM deep survey science with
current and forthcoming X-ray facilities.The Chandra Deep Field South (CDF-S) was observed by XMM-Newton for about 3 Ms in many periods over the past decade (2001–2002 and 2008–2009). The main goal of the survey was to obtain good quality X-ray spectroscopy of the active galactic nuclei responsible for the bulk of the X-ray background. We present the scientific highlights of the XMM-Newton survey and briefly discuss the perspectives of future observations to pursue XMM deep survey science with current and forthcoming X-ray facilities
The XMM deep survey in the Chandra Deep Field South
No full textThe Chandra Deep Field South (CDF-S) was observed by XMM-Newton for about 3Ms in many periods over the past decade (2001-2002 and 2008-2009). The main goal of the survey was to obtain good quality X-ray spectroscopy of the active galactic nuclei responsible for the bulk of the X-ray background. We present the scientific highlights of the XMM-Newton survey and briefly discuss the perspectives of future observations to pursue XMM deep survey science with current and forthcoming X-ray facilities
The Chandra deep field-south survey: 2 Ms source catalogs
Full text linkWe present point-source catalogs for the ~2 Ms exposure of the Chandra Deep Field-South (CDF-S) this is one of the two most sensitive X-ray surveys ever performed. The survey covers an area of ~436 arcmin2 and reaches on-axis sensitivity limits of ~1.9×10-17 and ~1.3×10-16 ergs cm-2 s-1 for the 0.5-2.0 and 2-8 keV bands, respectively. Four hundred and sixty-two X-ray point sources are detected in at least one of three X-ray bands that were searched; 135 of these sources are new compared to the previous ~1 Ms CDF-S detections. Source positions are determined using centroid and matched-filter techniques; the median positional uncertainty is ~0.36". The X-ray-to-optical flux ratios of the newly detected sources indicate a variety of source types; ~55% of them appear to be active galactic nuclei, while ~45% appear to be starburst and normal galaxies. In addition to the main Chandra catalog, we provide a supplementary catalog of 86 X-ray sources in the ~2 Ms CDF-S footprint that was created by merging the ~250 ks Extended Chandra Deep Field-South with the CDF-S this approach provides additional sensitivity in the outer portions of the CDF-S. A second supplementary catalog that contains 30 X-ray sources was constructed by matching lower significance X-ray sources to bright optical counterparts (R<23.8) the majority of these sources appear to be starburst and normal galaxies. The total number of sources in the main and supplementary catalogs is 578. Optical R-band counterparts and basic optical and infrared photometry are provided for the X-ray sources in the main and supplementary catalogs. We also include existing spectroscopic redshifts for 224 of the X-ray sources. The average backgrounds in the 0.5-2.0 and 2-8 keV bands are 0.066 and 0.167 counts Ms-1 pixel-1, respectively, and the background counts follow Poisson distributions. The effective exposure times and sensitivity limits of the CDF-S are now comparable to those of the ~2 Ms Chandra Deep Field-North (CDF-N). We also present cumulative number counts for the main catalog and compare the results to those for the CDF-N. The soft-band number counts for these two fields agree well with each other at fluxes higher than ~2×10-16 ergs cm-2 s-1, while the CDF-S number counts are up to ~25% smaller than those for the CDF-N at fluxes below ~2×10-16 ergs cm-2 s-1 in the soft band and ~2×10-15 ergs cm-2 s-1 in the hard band, suggesting small field-to-field variations
The Chandra Deep Field-South: The 1 million second exposure
No full textWe present the main results from our 940 ks observation of the Chandra Deep Field-South using the source catalog described in an accompanying paper by Giacconi et al. We extend the measurement of source number counts to 5.5 x 10(-17) ergs cm(-2) s(-1) in the soft 0.5-2 keV band and 4.5 x 10(-16) ergs cm(-2) s(-1) in the hard 2-10 keV band. The hard-band log N-log S shows a significant flattening (slope similar or equal to0.6) below approximate to10(-14) ergs cm(-2) s(-1), leaving at most 10%-15% of the X-ray background to be resolved, the main uncertainty lying in the measurement of the total flux of the X-ray background (XRB). On the other hand, the analysis in the very hard 5-10 keV band reveals a relatively steep log N-log S (slope similar or equal to1.3) down to 10(-15) ergs cm(-2) s(-1). Together with the evidence of a progressive flattening of the average X-ray spectrum near the flux limit, this indicates that there is still a nonnegligible population of faint hard sources to be discovered at energies not well probed by Chandra, which possibly contributes to the 30 keV bump in the spectrum of the XRB. We use optical redshifts and identifications, obtained with the Very Large Telescope, for one-quarter of the sample to characterize the combined optical and X-ray properties of the Chandra Deep Field-South sample. Different source types are well separated in a parameter space that includes X-ray luminosity, hardness ratio, and R-K color. Type II objects, while redder on average than the field population, have colors that are consistent with being hosted by a range of galaxy types. Type II active galactic nuclei are mostly found at z less than or similar to 1, in contrast with predictions based on active galactic nucleus population synthesis models, thus suggesting a revision of their evolutionary parameters
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