We present a study of the infrared properties of X-ray selected, moderate-luminosity (i.e. L
X= 1042-1044 erg s−1) active galactic nuclei (AGNs) up to z ≈ 3, in order to explore the links between ...star formation in galaxies and accretion on to their central black holes. We use 100 and 160 μ m fluxes from GOODS-Herschel - the deepest survey yet undertaken by the Herschel telescope - and show that in the vast majority of cases (i.e. >94 per cent) these fluxes are dominated by emission from the host galaxy. As such, these far-infrared bands provide an uncontaminated view of star formation in the AGN host galaxies. We find no evidence of any correlation between the X-ray and infrared luminosities of moderate AGNs at any redshift, suggesting that global star formation is decoupled from nuclear (i.e. AGN) activity in these galaxies. On the other hand, we confirm that the star formation rates of AGN hosts increase strongly with redshift, by a factor of 43+27
− 18 from z < 0.1 to z = 2-3 for AGNs with the same range of X-ray luminosities. This increase is entirely consistent with the factor of 25-50 increase in the specific star formation rates (SSFRs) of normal, star-forming (i.e. main-sequence) galaxies over the same redshift range. Indeed, the average SSFRs of AGN hosts are only marginally (i.e. ≈20 per cent) lower than those of main-sequence galaxies at all surveyed redshifts, with this small deficit being due to a fraction of AGNs residing in quiescent (i.e. low SSFR) galaxies. We estimate that 79 ± 10 per cent of moderate-luminosity AGNs are hosted in main-sequence galaxies, 15 ± 7 per cent in quiescent galaxies and <10 per cent in strongly starbursting galaxies. We derive the fractions of all main-sequence galaxies at z < 2 that are experiencing a period of moderate nuclear activity, noting that it is strongly dependent on galaxy stellar mass (M
stars), rising from just a few per cent at M
stars∼ 1010 M⊙ to ≳20 per cent at M
stars≥ 1011 M⊙. Our results indicate that it is galaxy stellar mass that is most important in dictating whether a galaxy hosts a moderate-luminosity AGN. We argue that the majority of moderate nuclear activity is fuelled by internal mechanisms rather than violent mergers, which suggests that high-redshift disc instabilities could be an important AGN feeding mechanism.
We present APEX LABOCA 870 μm observations of the field around the high-redshift radio galaxy MRC1138−262 at z = 2.16. We detect 16 submillimeter galaxies (SMGs) in this ~140 arcmin2 bolometer map ...with flux densities in the range 3–11 mJy. The raw number counts indicate a density of SMGs that is up to four times that of blank field surveys. Based on an exquisite multiwavelength database, including VLA 1.4 GHz radio and infrared observations, we investigate whether these sources are members of the protocluster structure at z ≈ 2.2. Using Herschel PACS and SPIRE and Spitzer MIPS photometry, we derive reliable far-infrared (FIR) photometric redshifts for all sources. Follow-up VLT ISAAC and SINFONI NIR spectra confirm that four of these SMGs have redshifts of z ≈ 2.2. We also present evidence that another SMG in this field, detected earlier at 850 μm, has a counterpart that exhibits Hα and CO(1–0) emission at z = 2.15. Including the radio galaxy and two SMGs with FIR photometric redshifts at z = 2.2, we conclude that at least eight submm sources are part of the protocluster at z = 2.16 associated with the radio galaxy MRC1138−262. We measure a star formation rate density SFRD ~1500 M⊙ yr-1 Mpc-3, four magnitudes higher than the global SFRD of blank fields at this redshift. Strikingly, these eight sources are concentrated within a region of 2 Mpc (the typical size of clusters in the local universe) and are distributed within the filaments traced by the HAEs at z ≈ 2.2. This concentration of massive, dusty starbursts is not centered on the submillimeter-bright radio galaxy which could support the infalling of these sources into the cluster center. Approximately half (6/11) of the SMGs that are covered by the Hα imaging data are associated with HAEs, demonstrating the potential of tracing SMG counterparts with this population. To summarize, our results demonstrate that submillimeter observations may enable us to study (proto)clusters of massive, dusty starbursts.
Many theoretical models require powerful active galactic nuclei (AGNs) to suppress star formation in distant galaxies and reproduce the observed properties of today's massive galaxies. A recent study ...based on Herschel-SPIRE submillimeter observations claimed to provide direct support for this picture, reporting a significant decrease in the mean star formation rates (SFRs) of the most luminous AGNs (L sub(X) > 10 super(44) erg s super(-1)) at z approximate 1-3 in the Chandra Deep Field-North (CDF-N). In this Letter, we extend these results using Herschel-SPIRE 250 mu m data in the COSMOS and Chandra Deep Field-South fields to achieve an order-of-magnitude improvement in the number of sources at L sub(X) > 10 super(44) erg s super(-1). On the basis of our analysis, we find no strong evidence for suppressed star formation in L sub(X) > 10 super(44) erg s super(-1) AGNs at z approximate 1-3. The mean SFRs of the AGNs are constant over the broad X-ray luminosity range of L sub(X) approximate 10 super(43)-10 super(45) erg s super(-1) (with mean SFRs consistent with typical star-forming galaxies at z approximate 2; left angle bracketSFRsright angle bracket approximate 100-200 M sub(middot in circle) yr super(-1)). We suggest that the previous CDF-N results were likely due to low number statistics. We discuss our results in the context of current theoretical models.
The European Space Agency (ESA) Planetary Science Archive (PSA) is undergoing a significant refactoring of all its components to improve the services provided to the scientific community and the ...public. The PSA supports ESA's missions exploring the Solar System by archiving scientific peer-reviewed observations as well as engineering data sets. This includes the Giotto, SMART-1, Huygens, Venus Express, Mars Express, Rosetta, Exomars 2016, Exomars RSP, BepiColombo, and JUICE missions. The PSA is offering a newly designed graphical user interface which is simultaneously meant to maximize the interaction with scientific observations and also minimise the efforts needed to download these scientific observations. The PSA still offers the same services as before (i.e., FTP, documentation, helpdesk, etc.). In addition, it will support the two formats of the Planetary Data System (i.e., PDS3 and PDS4), as well as providing new ways for searching the data products with specific metadata and geometrical parameters. As well as enhanced services, the PSA will also provide new services to improve the visualisation of data products and scientific content (e.g., spectra, etc.). Together with improved access to the spacecraft engineering data sets, the PSA will provide easier access to scientific data products that will help to maximize the science return of ESA's space missions.
•The PSA has changed his interface to improve science accessibility and discovery through ESA missions.•The PSA hosts close to 50 TB of data with almost 10 millions products.•The development of the PSA will provide a full multi-mission -instrument archive with geometrical and GIS capabilities.•Science ready products from comets, asteroids and planets are available for free.
Context. Dust attenuation curves in external galaxies are useful for studying their dust properties as well as interpreting their intrinsic spectral energy distributions. These functions are not very ...well known in the UV range whether at low or high redshift. In particular, the presence or absence of a UV bump at 2175 Å remains an open issue that has consequences on the interpretation of broad band colours of galaxies involving the UV range. Aims. We want to study the dust attenuation curve in the UV range at z > 1 where the UV is redshifted into the visible and with Herschel data to constrain dust emission and a global dust attenuation. In particular, we search for a UV bump and related implications for dust attenuation determinations. Methods. We use deep photometric data of the Chandra Deep Field South obtained with intermediate and broad band filters by the MUSYC project to sample the UV rest frame of galaxies with 1 < z < 2. Herschel/PACS and Spitzer/MIPS data are used to measure the dust emission. We select 30 galaxies with high S/N in all bands. Their SEDs from the UV to the far-IR are fitted using the CIGALE code and the characteristics of the dust attenuation curves obtained as Bayesian outputs of the SED fitting process. Results. The mean dust attenuation curve we derive exhibits a significant UV bump at 2175 Å whose amplitude corresponds to 35% (76%) that of the Milky Way (Large Magellanic Cloud: LMC2 supershell) extinction curve. An analytical expression of the average attenuation curve (A(λ)/AV) is given and found to be slightly steeper than the Calzetti et al. one, although at a 1σ level. Our galaxy sample is used to study the derivation of the slopes of the UV continuum from broad band colours, including the rest frame GALEX FUV − NUV colour. Systematic errors induced by the presence of the bump are quantified. We compare dust attenuation factors measured with CIGALE to the slope of the UV continuum and find that there is a large scatter around the relation valid for local starbursts (~0.7 mag). The uncertainties on the determination of the UV slope lead to an extra systematic error in a range of 0.3 to 0.7 mag on dust attenuation when a filter overlaps the UV bump.
Aims. We study the impact of galaxy-galaxy interactions on the far-infrared properties of galaxies and its evolution at 0 < z < 1.2. Methods. Using the high-z galaxies in the fields of Great ...Observatories Origins Deep Survey (GOODS) observed by the Herschel Space Observatory in the framework of the GOODS-Herschel key program and the local IRAS or AKARI-selected galaxies in the field of Sloan Digital Sky Survey Data Release 7, we investigate the dependence of galaxy properties on the morphology of and the distance to the nearest neighbor galaxy. Results. We find that the star-formation rates (SFRs) and the specific SFRs (SSFRs) of galaxies on average depend on the morphology of and the distance to the nearest neighbor galaxy in this redshift range. When a late-type galaxy has a close neighbor galaxy, the SFR and the SSFR increase as it approaches a late-type neighbor, which is supported by Kolmogorov-Smirnov (K-S) and Monte Carlo (MC) tests with a significance level of >99%. However, the SFR and the SSFR decrease or do not change much as the galaxy approaches an early-type neighbor. The bifurcations of SFRs and SSFRs depending on the neighbor’s morphology seem to occur at Rn ≈ 0.5rvir,nei (virial radius of the neighbor), which is supported by K-S and MC tests with a significance level of >98%. For all redshift bins, the SSFRs of late-type galaxies interacting with late-type neighbors are increased by factors of about 1.8 ± 0.7 and 4.0 ± 1.2 compared to those of non-interacting galaxies when the pair separation is smaller than 0.5rvir,nei and 0.1rvir,nei, respectively. The dust temperature of both local and high-z late-type galaxies that strongly interact with late-type neighbors (i.e. Rn ≤ 0.1rvir,nei) appears to be higher than that of non-interacting galaxies with a significance level of 96−99%. However, the dust temperature of local late-type galaxies that strongly interact with early-type neighbors seems to be lower than or similar to that of non-interacting galaxies. Conclusions. Our results suggest that galaxy-galaxy interactions and mergers have been strongly affecting the SFR and the dust properties of star-forming galaxies over at least 8 billion years.
We present a detailed study of the infrared spectral energy distribution of the high-redshift radio galaxy MRC 1138-26 at z = 2.156, also known as the Spiderweb Galaxy. By combining photometry from ...Spitzer, Herschel, and LABOCA we fit the rest-frame 5-300 mu m emission using a two-component, starburst, and active galactic nucleus (AGN) model. The total infrared (8-1000 mu m) luminosity of this galaxy is (1.97 + or - 0.28) x 10 super(13) L sub(middot in circle) with (1.17 + or - 0.27) and (0.79 + or - 0.09) x 10 super(13) L sub(middot in circle) due to the AGN and starburst components, respectively. The high derived AGN accretion rate of ~20% Eddington and the measured star formation rate (SFR) of 1390 + or - 150 M sub(middot in circle) yr super(-1) suggest that this massive system is in a special phase of rapid central black hole and host galaxy growth, likely caused by a gas-rich merger in a dense environment. The accretion rate is sufficient to power both the jets and the previously observed large outflow. The high SFR and strong outflow suggest that this galaxy could potentially exhaust its fuel for stellar growth in a few tens of Myr, although the likely merger of the radio galaxy with nearby satellites suggests that bursts of star formation may recur again on timescales of several hundreds of Myr. The age of the radio lobes implies the jet started after the current burst of star formation, and therefore we are possibly witnessing the transition from a merger-induced starburst phase to a radio-loud AGN phase. We also note tentative evidence for CII158 mu m emission. This paper marks the first results from the Herschel Galaxy Evolution Project (Project HeRGE), a systematic study of the evolutionary state of 71 high-redshift, 1 < z < 5.2, radio galaxies.
Aims. Star formation in massive galaxies is quenched at some point during hierarchical mass assembly. To understand where and when the quenching processes takes place, we study the evolution of the ...total star formation rate per unit total halo mass (Σ(SFR)/M) in three different mass scales: low mass halos (field galaxies), groups, and clusters, up to a redshift z ≈ 1.6. Methods. We use deep far-infrared PACS data at 100 and 160 μm to accurately estimate the total star formation rate of the luminous infrared galaxy population of 9 clusters with mass ~1015 M⊙, and 9 groups/poor clusters with mass ~5 × 1013 M⊙. Estimates of the field Σ(SFR)/M are derived from the literature, by dividing the star formation rate density by the mean comoving matter density of the universe. Results. The field Σ(SFR)/M increases with redshift up to z ~ 1 and it is constant thereafter. The evolution of the Σ(SFR)/M – z relation in galaxy systems is much faster than in the field. Up to redshift z ~ 0.2, the field has a higher Σ(SFR)/M than galaxy groups and galaxy clusters. At higher redshifts, galaxy groups and the field have similar Σ(SFR)/M, while massive clusters have significantly lower Σ(SFR)/M than both groups and the field. There is a hint of a reversal of the SFR activity vs. environment at z ~ 1.6, where the group Σ(SFR)/M lies above the field Σ(SFR)/M − z relation. We discuss possible interpretations of our results in terms of the processes of downsizing, and star-formation quenching.
Using extremely deep PACS 100- and 160 μm Herschel data from the GOODS-Herschel program, we identify 21 infrared bright galaxies previously missed in the deepest 24 μm surveys performed by ...Spitzer/MIPS. These MIPS dropouts are predominantly found in two redshift bins, centred at z ~ 0.4 and ~1.3. Their S100/S24 flux density ratios are similar to those of local (ultra-) luminous infrared galaxies (LIRGs and ULIRGs), whose silicate absorption features at 18 μm (at z ~ 0.4) and 9.7 μm (at z ~ 1.3) are shifted into the 24 μm MIPS band at these redshifts. The high-z sub-sample consists of 11 infrared luminous sources, accounting for ~2% of the whole GOODS-Herschel sample and putting strong upper limits on the fraction of LIRGs/ULIRGs at 1.0 < z < 1.7 that are missed by the 24 μm surveys. We find that a S100/S24 > 43 colour cut selects galaxies with a redshift distribution similar to that of the MIPS dropouts and when combined with a second colour cut, S16/S8 > 4, isolates sources at 1.0 < z < 1.7. We show that these sources have elevated specific star formation rates (sSFR) compared to main sequence galaxies at these redshifts and are likely to be compact starbursts with moderate/strong 9.7 μm silicate absorption features in their mid-IR spectra. Herschel data reveal that their infrared luminosities extrapolated from the 24 μm flux density are underestimated, on average, by a factor of ~3. These silicate break galaxies account for 16% (8%) of the ULIRG (LIRG) population in the GOODS fields, indicating a lower limit in their space density of 2.0 × 10-5 Mpc-3. Finally, we provide estimates of the fraction of z < 2 MIPS dropout sources as a function of the 24-, 100-, 160-, 250- and 350 μm sensitivity limits, and conclude that previous predictions of a population of silicate break galaxies missed by the major 24 μm extragalactic surveys have beenoverestimated.
We report the serendipitous detection of a significant overdensity of Herschel-Spectral and Photometric Imaging Receiver 250 μm sources in the vicinity of MRC 1138−26. We use an adaptive kernel ...density estimate to quantify the significance, including a comparison with other fields. The overdensity has a size of ∼3.5-4 arcmin and stands out at ∼5σ with respect to the background estimate. No features with similar significance were found in four Herschel-observed extragalactic control fields: GOODS-North, Lockman, COSMOS and UDS. The chance of having a similar overdensity in a field with the same number but randomly distributed sources is less than 2 per cent. The clump is also visible as a low-surface-brightness feature in the Planck 857 GHz map. We detect 76 sources at 250 μm (with a signal-to-noise ratio greater than 3), in a region of 4 arcmin radius (or 1.51 ± 0.17 arcmin−2); 43 of those (or 0.86 ± 0.13 arcmin−2) are above a flux density limit of 20 mJy. This is a factor of 3.6 in excess over the average 0.24 ± 0.02 arcmin−2 in the four control fields, considering only the sources above 20 mJy. We also find an excess in the number counts of sources with 250 μm flux densities between 30 and 40 mJy, compared to deep extragalactic blank-field number counts. Assuming a fixed dust temperature (30 K) and emissivity (β = 1.5), a crude, blackbody-derived redshift distribution, z
BB, of the detected sources is significantly different from the distributions in the control fields and exhibits a significant peak at z
BB 1.5, although the actual peak redshift is highly degenerate with the temperature. We tentatively suggest, based on z
BB and the similar S250/S350 colours of the sources within the peak, that a significant fraction of the sources in the clump may be at a similar redshift. Since the overdensity lies ∼ 7 arcmin south of the z = 2.16 Spiderweb protocluster MRC 1138−26, an intriguing possibility (that is presently unverifiable given the data in hand) is that it lies within the same large-scale structure.
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