Pathways to quiescence: SHARDS view on the star formation histories of massive quiescent galaxies at 1.0 < z < 1.5

We present star formation histories (SFHs) for a sample of 104 massive (stellar mass M > 10^10 M_⊙) quiescent galaxies (MQGs) at z = 1.0–1.5 from the analysis of spectrophotometric data from the Survey for High-z Absorption Red and Dead Sources (SHARDS) and HST/WFC3 G102 and G141 surveys of the GOODS-North field, jointly with broad-band observations from ultraviolet (UV) to far-infrared (far-IR). The sample is constructed on the basis of rest-frame UVJ colours and specific star formation rates (sSFRs = SFR/Mass). The spectral energy distributions (SEDs) of each galaxy are compared to models assuming a delayed exponentially declining SFH. A Monte Carlo algorithm characterizes the degeneracies, which we are able to break taking advantage of the SHARDS data resolution, by measuring indices such as MgUV and D4000. The population of MQGs shows a duality in their properties. The sample is dominated (85 per cent) by galaxies with young mass-weighted ages, t_M t_M < 2 Gyr, short star formation time-scales, 〈τ〉 ∼ 60–200 Myr, and masses log(M/M_⊙) ∼ 10.5. There is an older population (15 per cent) with t_M t_M = 2–4 Gyr, longer star formation time-scales, 〈τ〉∼ 400 Myr, and larger masses, log(M/M_⊙) ∼ 10.7. The SFHs of our MQGs are consistent with the slope and the location of the main sequence of star-forming galaxies at z > 1.0, when our galaxies were 0.5–1.0 Gyr old. According to these SFHs, all the MQGs experienced a luminous infrared galaxy phase that lasts for ∼500 Myr, and half of them an ultraluminous infrared galaxy phase for ∼100 Myr. We find that the MQG population is almost assembled at z ∼ 1, and continues evolving passively with few additions to the population.

The evolutionary paths among galaxy types on the red sequence at 0.3 < Z < 1.5

We have studied the main evolutionary paths among the galaxy types residing on the massive end of the Red Sequence and nearby locations on the Green Valley during the last ∼9 Gyr. The morphological and star formation properties of a sample of these galaxies at 0 . 3 < z < 1 .5 with stellar masses M_∗ > 5 × 10^10 M_⊙ have been analysed. We present direct observational evidence for the first time of the existence of two main evolutionary paths among the different red galaxy types since z ∼ 1 .5, which provide some clues on the nature of the processes that have governed the assembly of present-day massive quiescent galaxies. The results are in excellent agreement with the hierarchical evolutionary framework proposed in the Eliche-Moral et al. (2010) model. Data from SHARDS (one of the ESO/GTC Large Programmes approved in 2009A) will complement and improve the present findings, shedding some light into many of the still unsettled questions concerning the migration of galaxies from the Blue Cloud to the Red Sequence at z < 1 .5.

The X-ray outburst of the Galactic Centre magnetar SGR J1745−2900 during the first 1.5 year

In 2013 April a new magnetar, SGR 1745−2900, was discovered as it entered an outburst, at only 2.4 arcsec angular distance from the supermassive black hole at the centre of the Milky Way, Sagittarius A*. SGR 1745−2900 has a surface dipolar magnetic field of ∼2 × 1014 G, and it is the neutron star closest to a black hole ever observed. The new source was detected both in the radio and X-ray bands, with a peak X-ray luminosity LX ∼ 5 × 1035 erg s−1. Here we report on the long-term Chandra (25 observations) and XMM–Newton (eight observations) X-ray monitoring campaign of SGR 1745−2900 from the onset of the outburst in 2013 April until 2014 September. This unprecedented data set allows us to refine the timing properties of the source, as well as to study the outburst spectral evolution as a function of time and rotational phase. Our timing analysis confirms the increase in the spin period derivative by a factor of ∼2 around 2013 June, and reveals that a further increase occurred between 2013 October 30 and 2014 February 21. We find that the period derivative changed from 6.6 × 10−12 to 3.3 × 10−11 s s−1 in 1.5 yr. On the other hand, this magnetar shows a slow flux decay compared to other magnetars and a rather inefficient surface cooling. In particular, starquake-induced crustal cooling models alone have difficulty in explaining the high luminosity of the source for the first ∼200 d of its outburst, and additional heating of the star surface from currents flowing in a twisted magnetic bundle is probably playing an important role in the outburst evolution.

Herrn de la Cepede's Naturgeschichte der Amphibien, oder der enerlegenden vierfussigen Thiere und der Schlangen : Eine Fortsetzung von Buffon's Naturgeschichte / Aus dem französischen übersetzt ... von Johann Matthäus Bechstein. Bd. 1-5.

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Herrn de la Cepede's Naturgeschichte der Amphibien, oder der enerlegenden vierfussigen Thiere und der Schlangen : Eine Fortsetzung von Buffon's Naturgeschichte / Aus dem französischen übersetzt ... von Johann Matthäus Bechstein. Bd. 1-5.

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Herrn de la Cepede's Naturgeschichte der Amphibien, oder der enerlegenden vierfussigen Thiere und der Schlangen : Eine Fortsetzung von Buffon's Naturgeschichte / Aus dem französischen übersetzt ... von Johann Matthäus Bechstein. Bd. 1-5.

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Herrn de la Cepede's Naturgeschichte der Amphibien, oder der enerlegenden vierfussigen Thiere und der Schlangen : Eine Fortsetzung von Buffon's Naturgeschichte / Aus dem französischen übersetzt ... von Johann Matthäus Bechstein. Bd. 1-5.

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Testimonies of Students, Number 1-5, 1768 April

Handwritten testimonies of students regarding their actions during the rebellion. Each student's statement was numbered, and groups of statements were also assigned a number, as indicated in the list below.

Boston, Massachusetts Region, Digital Elevation Model (1:5,000), 2005 - Integer version

This raster layer represents surface elevation for the Boston Region, Massachusetts. This datalayer is a subset (covering only the Boston region) of the Massachusetts statewide digital elevation model. It was created from the digital terrain models that were produced as part of the 1:5,000 Black and White Digital Orthophoto imagery project. Cellsize is 5 meters by 5 meters. Each cell has an integer value, in meters, which represents its elevation above or below sea level.

Boston, Massachusetts Region 1:5,000 Color Ortho Imagery (1/2-meter Resolution), 2001

1/2-meter resolution 1:5,000 orthophoto image of the Boston region from April 2001. This datalayer is a subset (covering only the Boston region) of the Massachusetts statewide orthophoto image series available from MassGIS. It consists of 23 orthophoto quads mosaicked together (MassGIS orthophoto quad ID: 229890, 229894, 229898, 229902, 233886, 233890, 233894, 233898, 233902, 233906, 233910, 237890, 237894, 237898, 237902, 237906, 237910, 241890, 241894, 241898, 241902, 245898, 245902). These medium resolution true color images are considered the new "basemap" for the Commonwealth by MassGIS and the Executive Office of Environmental Affairs (EOEA). MassGIS/EOEA and the Massachusetts Highway Department jointly funded the project. The photography for the mainland was captured in April 2001 when deciduous trees were mostly bare and the ground was generally free of snow. The geographic extent of this dataset is the same as that of the MassGIS dataset: Boston, Massachusetts Region LIDAR First Return Elevation Data, 2002 [see cross references].